Provided by: s-nail_14.9.15-1_amd64 
NAME
S-nail [v14.9.15] — send and receive Internet mail
SYNOPSIS
s-nail [-DdEFinv~#] [-: spec] [-A account] [:-a attachment:] [:-b bcc-addr:] [:-C "field: body":]
[:-c cc-addr:] [-M type | -m file | -q file | -t] [-r from-addr] [:-S var[=value]:] [-s subject]
[:-T "field: addr":] [:-X cmd:] [:-Y cmd:] [-.] :to-addr: [-- :mta-option:]
s-nail [-DdEeHiNnRv~#] [-: spec] [-A account] [:-C "field: body":] [-L spec] [-r from-addr] [:-S
var[=value]:] [-u user] [:-X cmd:] [:-Y cmd:] [-- :mta-option:]
s-nail [-DdEeHiNnRv~#] [-: spec] [-A account] [:-C "field: body":] -f [-L spec] [-r from-addr] [:-S
var[=value]:] [:-X cmd:] [:-Y cmd:] [file] [-- :mta-option:]
s-nail -h | --help
s-nail -V | --version
DESCRIPTION
Note: S-nail (S-nail) will see major changes in v15.0 (circa 2020). Some backward
incompatibilities cannot be avoided. “COMMANDS” change to “Shell-style argument quoting”, and
shell metacharacters will become (more) meaningful. Some commands accept new syntax today via wysh
(“Command modifiers”). Behaviour is flagged [v15-compat] and [no v15-compat], setting v15-compat
(“INTERNAL VARIABLES”) will choose new behaviour when applicable; giving it a value makes wysh an
implied default. [Obsolete] flags what will vanish. Using -d or -v enables obsoletion warnings.
Warning! v15-compat (with value) will be a default in v14.10.0!
S-nail provides a simple and friendly environment for sending and receiving mail. It is intended to
provide the functionality of the POSIX mailx(1) command, but is MIME capable and optionally offers
extensions for line editing, S/MIME, SMTP and POP3, among others. S-nail divides incoming mail into its
constituent messages and allows the user to deal with them in any order. It offers many “COMMANDS” and
“INTERNAL VARIABLES” for manipulating messages and sending mail. It provides the user simple editing
capabilities to ease the composition of outgoing messages, and increasingly powerful and reliable non-
interactive scripting capabilities.
Options
-: spec, --resource-files=..
Explicitly control which of the “Resource files” shall be sourced (loaded): if the letter ‘s’
is (case-insensitively) part of the spec then the system wide s-nail.rc is sourced, likewise
the letter ‘u’ controls sourcing of the user's personal ~/.mailrc file, whereas the letters ‘-’
and ‘/’ explicitly forbid sourcing of any resource files. Scripts should use this option: to
avoid environmental noise they should “detach” from any configuration and create a script-
specific environment, setting any of the desired “INTERNAL VARIABLES” via -S and running
configurating commands via -X. This option overrides -n.
-A name, --account=..
Executes an account command for the given user email account name after program startup is
complete (all resource files are loaded, any -S setting is being established, but -X commands
have not been evaluated yet). Being a special incarnation of defined macros for the purpose of
bundling longer-lived settings, activating such an email account also switches to the accounts
“primary system mailbox” (most likely the inbox). If the operation fails the program will exit
if it is used non-interactively, or if any of errexit or posix are set.
-a file[=input-charset[#output-charset]], --attach=..
Attach file to the message (for compose mode opportunities refer to ~@ and ~^). “Filename
transformations” (also see file) will be performed, except that shell variables are not
expanded. Shall file not be accessible but contain a ‘=’ character, then anything before the
last ‘=’ will be used as the filename, anything thereafter as a character set specification.
If an input character set is specified, but no output character set, then the given input
character set is fixed as-is, and no conversion will be applied; giving the empty string or the
special string hyphen-minus ‘-’ will be treated as if ttycharset has been specified (the
default).
If an output character set has also been given then the conversion will be performed exactly as
specified and on-the-fly, not considering the file type and content. As an exception the empty
string or hyphen-minus ‘-’, select the default conversion algorithm (see “Character sets”): no
conversion is performed on-the-fly, file and its contents will be MIME-classified (“HTML mail
and MIME attachments, The mime.types files”); Only this mode is supported without support for
character set conversions (features does not mention ‘+iconv’).
-B ([Obsolete]: S-nail will always use line-buffered output, to gain line-buffered input even in
batch mode enable batch mode via -#.)
-b addr, --bcc=..
Send a blind carbon copy to recipient addr, if the setting of expandaddr, one of the “INTERNAL
VARIABLES”, allows; the ‘shquote’ expandaddr flag is supported. The option may be used
multiple times. Also see the section “On sending mail, and non-interactive mode”.
-C "field: body", --custom-header=..
Create a custom header which persists for an entire session. A custom header consists of the
field name followed by a colon ‘:’ and the field content body, e.g., ‘-C "Blah: Neminem laede;
imo omnes, quantum potes, juva"’. Standard header field names cannot be overwritten by custom
headers. Runtime adjustable custom headers are available via the variable customhdr, and in
compose mode ~^, one of the “COMMAND ESCAPES”, as well as digmsg are the most flexible and
powerful options to manage message headers. This option may be used multiple times.
-c addr, --cc=..
Just like -b, except it places the argument in the list of carbon copies.
-D, --disconnected
([Option]) Startup with disconnected set.
-d, --debug
Almost enable a sandbox mode with the internal variable debug; the same can be achieved via ‘-S
debug’ or ‘set debug’.
-E, --discard-empty-messages
set skipemptybody and thus discard messages with an empty message part body.
-e, --check-and-exit
Just check if mail is present (in the system inbox or the one specified via -f): if yes, return
an exit status of zero, a non-zero value otherwise. To restrict the set of mails to consider
in this evaluation a message specification can be added with the option -L. Quickrun: does not
open an interactive session.
-F Save the message to send in a file named after the local part of the first recipient's address
(instead of in record).
-f, --file
Read in the contents of the user's “secondary mailbox” MBOX (or the specified file) for
processing; when S-nail is quit, it writes undeleted messages back to this file (but be aware
of the hold option). The optional file argument will undergo some special “Filename
transformations” (as via file). Note that file is not an argument to the flag -f, but is
instead taken from the command line after option processing has been completed. In order to
use a file that starts with a hyphen-minus, prefix with a relative path, as in
‘./-hyphenbox.mbox’.
-H, --header-summary
Display a summary of headers for the given file (depending on -u, inbox or MAIL, or as
specified via -f), then exit. A configurable summary view is available via the option -L.
This mode does not honour showlast. Quickrun: does not open an interactive session.
-h, --help
Show a brief usage summary; use --long-help for a list long options.
-i set ignore to ignore tty interrupt signals.
-L spec, --header-search=..
Display a summary of headers of all messages that match the given spec in the file found by the
same algorithm used by -H, then exit. See the section “Specifying messages” for the format of
spec. This mode does not honour showlast.
If the -e option has been given in addition no header summary is produced, but S-nail will
instead indicate via its exit status whether spec matched any messages (‘0’) or not (‘1’); note
that any verbose output is suppressed in this mode and must instead be enabled explicitly
(e.g., by using the option -v). Quickrun: does not open an interactive session.
-M type Special send mode that will flag standard input with the MIME ‘Content-Type:’ set to the given
known type (“HTML mail and MIME attachments, The mime.types files”) and use it as the main
message body. [v15 behaviour may differ] Using this option will bypass processing of
message-inject-head and message-inject-tail. Also see -q, -m, -t.
-m file Special send mode that will MIME classify the specified file, and use it as the main message
body. [v15 behaviour may differ] Using this option will bypass processing of
message-inject-head and message-inject-tail. Also see -q, -M, -t.
-N, --no-header-summary
inhibit the initial display of message headers when reading mail or editing a mailbox folder by
calling unset for the internal variable header.
-n Standard flag that inhibits reading the system wide s-nail.rc upon startup. The option -:
allows more control over the startup sequence; also see “Resource files”.
-q file, --quote-file=..
Special send mode that will initialize the message body with the contents of the specified
file, which may be standard input ‘-’ only in non-interactive context. Also see -M, -m, -t.
-R, --read-only
Any mailbox folder aka file opened will be in read-only mode.
-r from-addr, --from-address=..
Whereas the source address that appears in the from header of a message (or in the sender
header if the former contains multiple addresses) is honoured by the built-in SMTP transport,
it is not used by a file-based mta (Mail-Transfer-Agent) for the RFC 5321 reverse-path used for
relaying and delegating a message to its destination(s), for delivery errors etc., but it
instead uses the local identity of the initiating user.
When this command line option is used the given single addressee from-addr will be assigned to
the internal variable from, but in addition the command line option -f from-addr will be passed
to a file-based mta whenever a message is sent. Shall from-addr include a user name the
address components will be separated and the name part will be passed to a file-based mta
individually via -F name. Even though not a recipient the ‘shquote’ expandaddr flag is
supported.
If an empty string is passed as from-addr then the content of the variable from (or, if that
contains multiple addresses, sender) will be evaluated and used for this purpose whenever the
file-based mta is contacted. By default, without -r that is, neither -f nor -F command line
options are used when contacting a file-based MTA, unless this automatic deduction is enforced
by seting the internal variable r-option-implicit.
Remarks: many default installations and sites disallow overriding the local user identity like
this unless either the MTA has been configured accordingly or the user is member of a group
with special privileges. Passing an invalid address will cause an error.
-S var[=value], --set=..
set (or, with a prefix string ‘no’, as documented in “INTERNAL VARIABLES”, unset) variable and
optionally assign value, if supported; [v15 behaviour may differ] the entire expression is
evaluated as if specified within dollar-single-quotes (see “Shell-style argument quoting”) if
the internal variable v15-compat is set. If the operation fails the program will exit if any
of errexit or posix are set. Settings established via -S cannot be changed from within
“Resource files” or an account switch initiated by -A. They will become mutable again before
commands registered via -X are executed.
-s subject, --subject=..
Specify the subject of the message to be sent. Newline (NL) and carriage-return (CR) bytes are
invalid and will be normalized to space (SP) characters.
-T "field: addr", --target=..
Add addr to the list of receivers targeted by field, for now supported are only ‘bcc’, ‘cc’,
‘fcc’, and ‘to’. Field and body (address) are separated by a colon ‘:’ and optionally blank
(space, tabulator) characters. The ‘shquote’ expandaddr flag is supported. addr is parsed
like a message header address line, as if it would be part of a template message fed in via -t,
and the same modifier suffix is supported. This option may be used multiple times.
-t, --template
The text message given (on standard input) is expected to contain, separated from the message
body by an empty line, one or multiple plain text message headers. [v15 behaviour may differ]
Readily prepared MIME mail messages cannot be passed. Headers can span multiple consecutive
lines if follow lines start with any amount of whitespace. A line starting with the number
sign ‘#’ in the first column is ignored. Message recipients can be given via the message
headers ‘To:’, ‘Cc:’, ‘Bcc:’ (the ‘?single’ modifier enforces treatment as a single addressee,
e.g., ‘To?single: exa, <m@ple>’) or ‘Fcc:’, they will be added to any recipients specified on
the command line, and are likewise subject to expandaddr validity checks. If a message subject
is specified via ‘Subject:’ then it will be used in favour of one given on the command line.
More optional headers are ‘Reply-To:’ (possibly overriding reply-to), ‘Sender:’ (sender),
‘From:’ (from and / or option -r). ‘Message-ID:’, ‘In-Reply-To:’, ‘References:’ and
‘Mail-Followup-To:’, by default created automatically dependent on message context, will be
used if specified (a special address massage will however still occur for the latter). Any
other custom header field (also see -C, customhdr and ~^) is passed through entirely unchanged,
and in conjunction with the options -~ or -# it is possible to embed “COMMAND ESCAPES”. Also
see -M, -m, -q.
-u user, --inbox-of=..
Initially read the “primary system mailbox” of user, appropriate privileges presumed;
effectively identical to ‘-f %user’.
-V, --version
Show S-nails version and exit. The command version will also show the list of features: ‘$
s-nail -:/ -Xversion -Xx’.
-v, --verbose
setting the internal variable verbose enables display of some informational context messages.
(Will increase the level of verbosity when used multiple times.)
-X cmd, --startup-cmd=..
Add the given (or multiple for a multiline argument) cmd to a list of commands to be executed
before normal operation starts. The commands will be evaluated as a unit, just as via source.
Correlates with -# and errexit.
-Y cmd, --cmd=..
Add the given (or multiple for a multiline argument) cmd to a list of commands to be executed
after normal operation has started. The commands will be evaluated successively in the given
order, and as if given on the program's standard input — before interactive prompting begins in
interactive mode, after standard input has been consumed otherwise.
-~, --enable-cmd-escapes
Enable “COMMAND ESCAPES” in compose mode even in non-interactive use cases. This can be used
to, e.g., automatically format the composed message text before sending the message:
$ ( echo 'line one. Word. Word2.';\
echo '~| /usr/bin/fmt -tuw66' ) |\
LC_ALL=C s-nail -d~:/ -Sttycharset=utf-8 bob@exam.ple
-#, --batch-mode
Enables batch mode: standard input is made line buffered, the complete set of (interactive)
commands is available, processing of “COMMAND ESCAPES” is enabled in compose mode, and diverse
“INTERNAL VARIABLES” are adjusted for batch necessities, exactly as if done via -S: emptystart,
noerrexit, noheader, noposix, quiet, sendwait, typescript-mode as well as MAIL, MBOX and inbox
(the latter three to /dev/null). Also, the values of COLUMNS and LINES are looked up, and
acted upon. The following prepares an email message in a batched dry run:
$ LC_ALL=C printf 'm bob\n~s ubject\nText\n~.\nx\n' |\
LC_ALL=C s-nail -d#:/ -X'alias bob bob@exam.ple'
-., --end-options
This flag forces termination of option processing in order to prevent “option injection”
(attacks). It also forcefully puts S-nail into send mode, see “On sending mail, and non-
interactive mode”.
All given to-addr arguments and all receivers established via -b and -c as well as -T are subject to the
checks established by expandaddr, one of the “INTERNAL VARIABLES”; they all support the flag ‘shquote’.
If the setting of expandargv allows their recognition all mta-option arguments given at the end of the
command line after a ‘--’ separator will be passed through to a file-based mta (Mail-Transfer-Agent) and
persist for the entire session. expandargv constraints do not apply to the content of mta-arguments.
A starter
S-nail is a direct descendant of BSD Mail, itself a successor to the Research Unix mail which “was there
from the start” according to “HISTORY”. It thus represents the user side of the Unix mail system,
whereas the system side (Mail-Transfer-Agent, MTA) was traditionally taken by sendmail(8), and most MTAs
provide a binary of this name for compatibility purposes. If the [Option]al SMTP mta is included in the
features of S-nail then the system side is not a mandatory precondition for mail delivery.
Because S-nail strives for compliance with POSIX mailx(1) it is likely that some configuration settings
have to be adjusted before using it is a smooth experience. (Rather complete configuration examples can
be found in the section “EXAMPLES”.) The provided global s-nail.rc (one of the “Resource files”)
template bends those standard imposed settings of the “INTERNAL VARIABLES” a bit towards more user
friendliness and safety, however.
For example, it sets hold and keepsave in order to suppress the automatic moving of messages to the
“secondary mailbox” MBOX that would otherwise occur (see “Message states”), and keep to not remove empty
system MBOX mailbox files (or all empty such files if posix aka POSIXLY_CORRECT mode has been enabled) to
avoid mangling of file permissions when files eventually get recreated.
To enter interactive mode even if the initial mailbox is empty it sets emptystart, editheaders to allow
editing of headers as well as fullnames to not strip down addresses in compose mode, and quote to include
the message that is being responded to when replying, which is indented by an indentprefix that also
deviates from standard imposed settings. mime-counter-evidence is fully enabled, too.
Some random remarks. The file mode creation mask can be managed explicitly via the variable umask.
Files and shell pipe output can be sourced for evaluation, also during startup from within the “Resource
files”.
On sending mail, and non-interactive mode
To send a message to one or more people, using a local or built-in mta (Mail-Transfer-Agent) transport to
actually deliver the generated mail message, S-nail can be invoked with arguments which are the names of
people to whom the mail will be sent, and the command line options -b and -c can be used to add (blind)
carbon copy receivers:
# Via test MTA
$ echo Hello, world | s-nail -:/ -Smta=test -s test $LOGNAME
# Via sendmail(1) MTA
$ </dev/null s-nail -:/ -s test $LOGNAME
# Debug dry-run mode:
$ </dev/null LC_ALL=C s-nail -d -:/ \
-Sttycharset=utf8 -Sfullnames \
-b bcc@exam.ple -c cc@exam.ple -. \
'(Lovely) Bob <bob@exam.ple>' eric@exam.ple
# With SMTP (no real sending due to -d debug dry-run)
$ LC_ALL=C s-nail -d -:/ -Sv15-compat -Sttycharset=utf8 \
-S mta=smtps://mylogin@exam.ple:465 -Ssmtp-auth=none \
-S from=scriptreply@exam.ple \
-a /etc/mail.rc -. \
eric@exam.ple < /tmp/letter.txt
If standard input is a terminal rather than the message to be sent, the user is expected to type in the
message contents. In this compose mode S-nail treats lines beginning with the character ‘~’ special –
these are so-called “COMMAND ESCAPES”, which can be used to read in files, process shell commands, add
and edit attachments and more; e.g., ~v or ~e will start the VISUAL text EDITOR, respectively, to revise
the message in its current state, ~h allows editing of the most important message headers, with the
potent ~^ custom headers can be created, for example (more specifically than with -C and customhdr).
[Option]ally ~? gives an overview of most other available command escapes.
The command escape ~. (see there) will call hooks, insert automatic injections and receivers, leave
compose mode and send the message once it is completed. Aborting letter composition is possible with
either of ~x or ~q, the latter of which will save the message in the file denoted by DEAD unless nosave
is set. And unless ignoreeof is set the effect of ~. can also be achieved by typing end-of-transmission
(EOT) via ‘control-D’ (‘^D’) at the beginning of an empty line, and ~q is always reachable by typing end-
of-text (ETX) twice via ‘control-C’ (‘^C’).
A number of “ENVIRONMENT” and “INTERNAL VARIABLES” can be used to alter default behavior. setting (also
via -S) editalong will automatically startup an editor when compose mode is entered, and editing of
headers additionally to plain body content can be enabled via editheaders: [v15 behaviour may differ]
some, but not all headers can be created, edited or deleted in an editor, then. askcc and askbcc will
cause the user to be prompted actively for (blind) carbon-copy recipients, respectively, and (the
default) asksend will request confirmation whether the message shall be sent.
The envelope sender address is defined by from, explicitly defining an originating hostname may be
desirable, especially with the built-in SMTP Mail-Transfer-Agent mta. “Character sets” for outgoing
message and MIME part content are configurable via sendcharsets, whereas input data is assumed to be in
ttycharset. Message data will be passed over the wire in a mime-encoding. MIME parts aka attachments
need to be assigned a mimetype, usually taken out of “The mime.types files”. Saving a copy of sent
messages in a record mailbox may be desirable – as for most mailbox file targets the value will undergo
“Filename transformations”. Some introductional -d or debug sandbox dry-run tests will prove
correctness.
Message recipients are subject to alternates filtering, and may not only be email addresses, but can also
be names of mailboxes and even complete shell command pipe specifications. If the variable expandaddr is
not set then only email addresses like ‘bob@exam.ple’ and plain user names (including MTA aliases) may be
used, other types will be filtered out, giving a warning message. expandaddr indeed allows further
control over and adjustments of message recipients, e.g., user names can be expanded to network addresses
by specifying ‘namehostex’. A network address that contains no domain-, but only a valid local user
‘<name>’ in angle brackets will be automatically expanded to a valid address when hostname is not set, or
set to a non-empty value; setting it to the empty value instructs S-nail that the used mta will perform
the necessary expansion. The command addrcodec may help to generate standard compliant network
addresses.
If the variable expandaddr is set then an extended set of recipient addresses will be accepted: Any name
that starts with a vertical bar ‘|’ character specifies a command pipe – the command string following the
‘|’ is executed and the message is sent to its standard input; Likewise, any name that consists only of
hyphen-minus ‘-’ or starts with the character solidus ‘/’ or the character sequence dot solidus ‘./’ is
treated as a file, regardless of the remaining content. Any other name which contains a commercial at
‘@’ character is a network address; Any other name which starts with a plus sign ‘+’ character is a
mailbox name; Any other name which contains a solidus ‘/’ character but no exclamation mark ‘!’ or
percent sign ‘%’ character before is also a mailbox name; What remains is treated as a network address.
$ echo bla | s-nail -Sexpandaddr -s test ./mbox.mbox
$ echo bla | s-nail -Sexpandaddr -s test '|cat >> ./mbox.mbox'
$ echo safe | LC_ALL=C \
s-nail -:/ -Sv15-compat -Sttycharset=utf8 \
--set mime-force-sendout \
-Sexpandaddr=fail,-all,+addr,failinvaddr -s test \
-. bob@exam.ple
To create file-carbon-copies the special recipient header ‘Fcc:’ may be used as often as desired. Its
entire value (or body in standard terms) is interpreted as a file target, after having been subject to
“Filename transformations”. Beside using the command escape ~^ (to create a ‘Fcc’ header) this is the
only way to create a file-carbon-copy without introducing an ambiguity regarding the interpretation of
the address, e.g., to use file names with leading vertical bars or commercial ats. Like all other
recipients ‘Fcc:’ is subject to the checks of expandaddr. Any local file and pipe command addressee
honours the setting of mbox-fcc-and-pcc.
It is possible to create personal distribution lists via the alias command, so that, for instance, the
user can send mail to ‘cohorts’ and have it go to a group of people. Different to the alias mechanism of
most local mtas, often documented in aliases(5) and subject to the ‘name’ constraint of expandaddr,
personal aliases will be expanded by S-nail before the message is sent. They are thus a convenient
alternative to specifying each addressee by itself, correlate with the active set of alternates, and are
subject to metoo filtering. [Option]ally MTA aliases can be expanded before sending messages by setting
mta-aliases.
? alias cohorts bill jkf mark kridle@ucbcory ~/cohorts.mbox
? alias mark mark@exam.ple
? set mta-aliases=/etc/aliases
For the purpose of arranging a complete environment of settings that can be switched to with a single
command or command line option there are accounts. Alternatively it is also possible to use a flat
configuration, making use of so-called variable chains which automatically pick ‘USER@HOST’ or ‘HOST’
context-dependent variable variants: for example addressing ‘File pop3://yaa@exam.ple’ would find
pop3-no-apop-yaa@exam.ple, pop3-no-apop-exam.ple and pop3-no-apop in order. See “On URL syntax and
credential lookup” and “INTERNAL VARIABLES”.
The compose mode hooks on-compose-enter, on-compose-splice, on-compose-leave and on-compose-cleanup may
be set to defined macros and provide reliable and increasingly powerful mechanisms to perform automated
message adjustments dependent on message context, for example addition of message signatures
(message-inject-head, message-inject-tail) or creation of additional receiver lists (also by setting
autocc, autobcc). To achieve that the command digmsg may be used in order to query and adjust status of
message(s). The splice hook can also make use of “COMMAND ESCAPES”. ([v15 behaviour may differ] The
compose mode hooks work for forward, mail, reply and variants; resend and Resend only provide the hooks
on-resend-enter and on-resend-cleanup, which are pretty restricted due to the nature of the operation.)
To avoid environmental noise scripts should “detach” S-nail from any configuration files and create a
script-local environment, ideally with the command line options -: to disable any configuration file in
conjunction with repetitions of -S to specify variables:
$ env LC_ALL=C s-nail -:/ \
-Sv15-compat \
-Sttycharset=utf-8 -Smime-force-sendout \
-Sexpandaddr=fail,-all,failinvaddr \
-S mta=smtps://mylogin@exam.ple:465 -Ssmtp-auth=login \
-S from=scriptreply@exam.ple \
-s 'Subject to go' -a attachment_file \
-Sfullnames -. \
'Recipient 1 <rec1@exam.ple>' rec2@exam.ple \
< content_file
As shown, scripts can “fake” a locale environment, the above specifies the all-compatible 7-bit clean
LC_ALL “C”, but will nonetheless take and send UTF-8 in the message text by using ttycharset. If
character set conversion is compiled in (features includes the term ‘+iconv’) invalid (according to
ttycharset) character input data would normally cause errors; setting mime-force-sendout will instead, as
a last resort, classify the input as binary data, and therefore allow message creation to be successful.
(Such content can then be inspected either by installing a pipe-TYPE/SUBTYPE handler for
‘application/octet-stream’, or possibly automatically through mime-counter-evidence).
In interactive mode, which is introduced in the next section, messages can be sent by calling the mail
command with a list of recipient addresses:
$ s-nail -d -Squiet -Semptystart
"/var/spool/mail/user": 0 messages
? mail "Recipient 1 <rec1@exam.ple>", rec2@exam.ple
...
? # Will do the right thing (tm)
? m rec1@exam.ple rec2@exam.ple
On reading mail, and interactive mode
When invoked without addressees S-nail enters interactive mode in which mails may be read. When used
like that the user's system inbox (for more on mailbox types please see the command file) is read in and
a one line header of each message therein is displayed if the variable header is set. The visual style
of this summary of headers can be adjusted through the variable headline and the possible sorting
criterion via autosort. Scrolling through screenfuls of headers can be performed with the command z. If
the initially opened mailbox is empty S-nail will instead exit immediately (after displaying a message)
unless the variable emptystart is set.
At the prompt the command list will give a listing of all available commands and help will [Option]ally
give a summary of some common ones. If the [Option]al documentation strings are available (see features)
one can type ‘help X’ (or ‘?X’) and see the actual expansion of ‘X’ and what its purpose is, i.e.,
commands can be abbreviated (note that POSIX defines some abbreviations, so that the alphabetical order
of commands does not necessarily relate to the abbreviations; it is however possible to define overwrites
with commandalias). These commands can also produce a more verbose output.
Messages are given numbers (starting at 1) which uniquely identify messages; the current message – the
“dot” – will either be the first new message, or the first unread message, or the first message of the
mailbox; the internal variable showlast will instead cause usage of the last message for this purpose.
The command headers will display a screenful of header summaries containing the “dot”, whereas from will
display only the summaries of the given messages, defaulting to the “dot”.
Message content can be displayed with the command type (‘t’, alias print). Here the variable crt
controls whether and when S-nail will use the configured PAGER for display instead of directly writing to
the user terminal screen, the sole difference to the command more, which will always use the PAGER. The
command top will instead only show the first toplines of a message (maybe even compressed if topsqueeze
is set). Message display experience may improve by setting and adjusting mime-counter-evidence, and also
see “HTML mail and MIME attachments”.
By default the current message (“dot”) is displayed, but like with many other commands it is possible to
give a fancy message specification (see “Specifying messages”), e.g., ‘t:u’ will display all unread
messages, ‘t.’ will display the “dot”, ‘t 1 5’ will type the messages 1 and 5, ‘t 1-5’ will type the
messages 1 through 5, and ‘t-’ and ‘t+’ will display the previous and the next message, respectively.
The command search (a more substantial alias for from) will display a header summary of the given message
specification list instead of their content, e.g., the following will search for subjects:
? from '@Some subject to search for'
In the default setup all header fields of a message will be typed, but fields can be white- or
blacklisted for a variety of applications by using the command headerpick, e.g., to restrict their
display to a very restricted set for type: ‘headerpick type retain from to cc subject’. In order to
display all header fields of a message regardless of currently active ignore or retain lists, use the
commands Type and Top; Show will show the raw message content. Note that historically the global
s-nail.rc not only adjusts the list of displayed headers, but also sets crt. ([v15 behaviour may differ]
A yet somewhat restricted) Reliable scriptable message inspection is available via digmsg.
Dependent upon the configuration a line editor (see the section “On terminal control and line editor”)
aims at making the user experience with the many “COMMANDS” a bit nicer. When reading the system inbox,
or when -f (or file) specified a mailbox explicitly prefixed with the special ‘%:’ modifier (to propagate
it to a “primary system mailbox”), then messages which have been read (see “Message states”) will be
automatically moved to a “secondary mailbox”, the user's MBOX file, when the mailbox is left, either by
changing the active mailbox or by quitting S-nail – this automatic moving from a system- or primary- to
the secondary mailbox is not performed when the variable hold is set. Messages can also be explicitly
moved to other mailboxes, whereas copy keeps the original message. write can be used to write out data
content of specific parts of messages.
After examining a message the user can reply ‘r’ to the sender and all recipients (which will also be
placed in ‘To:’ unless recipients-in-cc is set), or Reply ‘R’ exclusively to the sender(s). The command
Lreply knows how to apply a special addressee massage, see “Mailing lists”. Dependent on the presence
and value of quote the message being replied to will be included in a quoted form. forwarding a message
will allow editing the new message: the original message will be contained in the message body, adjusted
according to headerpick. It is possible to resend or Resend messages: the former will add a series of
‘Resent-’ headers, whereas the latter will not; different to newly created messages editing is not
possible and no copy will be saved even with record unless the additional variable record-resent is set.
When sending, replying or forwarding messages comments and full names will be stripped from recipient
addresses unless the internal variable fullnames is set.
Of course messages can be delete ‘d’, and they can spring into existence again via undelete, or when the
S-nail session is ended via the exit or xit commands to perform a quick program termation. To end a mail
processing session regulary and perform a full program exit one may issue the command quit. It will,
among others, move read messages to the “secondary mailbox” MBOX as necessary, discard deleted messages
in the current mailbox, and update the [Option]al (see features) line editor history-file. By the way,
whenever the main event loop is about to look out for the next input line it will trigger the hook
on-main-loop-tick.
HTML mail and MIME attachments
Messages which are HTML-only become more and more common, and of course many messages come bundled with a
bouquet of MIME (Multipurpose Internet Mail Extensions) parts. To get a notion of MIME types S-nail has
a default set of types built-in, onto which the content of “The mime.types files” will be added (as
configured and allowed by mimetypes-load-control). Types can also become registered with the command
mimetype. To improve interaction with faulty MIME part declarations which are often seen in real-life
messages, setting mime-counter-evidence will allow verification of the given assertion, and possible
provision of an alternative, better MIME type.
Whereas S-nail [Option]ally supports a simple HTML-to-text filter for displaying HTML messages (indicated
by ‘+filter-html-tagsoup’ in features), it cannot handle MIME types other than plain text itself.
Instead programs need to become registered to deal with specific MIME types or file extensions. These
programs may either prepare plain text versions of their input in order to enable S-nail to integrate
their output neatlessly in its own message visualization (a mode which is called copiousoutput), or
display the content themselves, for example in an external graphical window: such handlers will only be
considered by and for the command mimeview.
To install a handler program for a specific MIME type an according pipe-TYPE/SUBTYPE variable needs to be
set; to instead define a handler for a specific file extension the respective pipe-EXTENSION variable can
be used – these handlers take precedence. [Option]ally S-nail supports mail user agent configuration as
defined in RFC 1524; this mechanism (see “The Mailcap files”) will be queried for display or quote
handlers if none of the former two did; it will be the sole source for handlers of other purpose. A last
source for handlers is the MIME type definition itself, if a type-marker has been registered with the
command mimetype, which many of the built-in MIME types do.
For example, to display a HTML message inline (converted to a more fancy plain text representation than
the built-in filter is capable to produce) with either of the text-mode browsers lynx(1) or elinks(1),
teach S-nail about MathML documents and make it display them as plain text, and to open PDF attachments
in an external PDF viewer, asynchronously and with some other magic attached:
? if [ "$features" !% +filter-html-tagsoup ]
? #set pipe-text/html='?* elinks -force-html -dump 1'
? set pipe-text/html='?* lynx -stdin -dump -force_html'
? # Display HTML as plain text instead
? #set pipe-text/html=?
? endif
? mimetype ? application/mathml+xml mathml
? wysh set pipe-application/pdf='?&=? \
trap "rm -f \"${MAILX_FILENAME_TEMPORARY}\"" EXIT;\
trap "trap \"\" INT QUIT TERM; exit 1" INT QUIT TERM;\
mupdf "${MAILX_FILENAME_TEMPORARY}"'
Mailing lists
Known or subscribed-to mailing lists may be flagged in the summary of headers (headline format character
‘%L’), and will gain special treatment when sending mails: the variable followup-to-honour will ensure
that a ‘Mail-Followup-To:’ header is honoured when a message is being replied to (reply and Lreply), and
followup-to controls creation of this header when creating mails, if the necessary user setup (from,
sender); is available; then, it may also be created automatically, e.g., when list-replying via Lreply,
when reply is used and the messages ‘Mail-Followup-To:’ is honoured etc.
The commands mlist and mlsubscribe manage S-nails notion of which addresses are mailing lists. With the
[Option]al regular expression support any such address which contains magic regular expression characters
(‘^[]*+?|$’; see re_format(7) or regex(7), dependent on the host system) will be compiled and used as
one, possibly matching many addresses.
? set followup-to followup-to-honour=ask-yes \
reply-to-honour=ask-yes
? mlist a1@b1.c1 a2@b2.c2 '.*@lists\.c3$'
? mlsubscribe a4@b4.c4 exact@lists.c3
Known and subscribed lists differ in that for the latter the users address is not part of a generated
‘Mail-Followup-To:’. There are exceptions, for example if multiple lists are addressed and not all have
the subscription attribute. When replying to a message its list address (‘List-Post:’ header) is
automatically and temporarily treated like a known mlist; dependent on the variable reply-to-honour an
existing ‘Reply-To:’ is used instead (if it is a single address on the same domain as ‘List-Post:’) in
order to accept a list administrator's wish that is supposed to have been manifested like that.
For convenience and compatibility with mail programs that do not honour the non-standard M-F-T, an
automatic user entry in the carbon-copy ‘Cc:’ address list of generated message can be created by setting
followup-to-add-cc. This entry will be added whenever the user will be placed in the ‘Mail-Followup-To:’
list, and is not a regular addressee already.
Signed and encrypted messages with S/MIME
[Option] S/MIME provides two central mechanisms: message signing and message encryption. A signed
message contains some data in addition to the regular text. The data can be used to verify that the
message has been sent using a valid certificate, that the sender address matches that in the certificate,
and that the message text has not been altered. Signing a message does not change its regular text; it
can be read regardless of whether the recipients software is able to handle S/MIME. It is thus usually
possible to sign all outgoing messages if so desired.
Encryption, in contrast, makes the message text invisible for all people except those who have access to
the secret decryption key. To encrypt a message, the specific recipients public encryption key must be
known. It is therefore not possible to send encrypted mail to people unless their key has been retrieved
from either previous communication or public key directories. Because signing is performed with private
keys, and encryption with public keys, messages should always be signed before becoming encrypted.
A central concept to S/MIME is that of the certification authority (CA). A CA is a trusted institution
that issues certificates. For each of these certificates it can be verified that it really originates
from the CA, provided that the CA's own certificate is previously known. A set of CA certificates is
usually delivered and installed together with the cryptographical library that is used on the local
system. Therefore reasonable security for S/MIME on the Internet is provided if the source that provides
that library installation is trusted. It is also possible to use a specific pool of trusted
certificates. If this is desired, smime-ca-no-defaults should be set to avoid using the default
certificate pool, and smime-ca-file and/or smime-ca-dir should be pointed to a trusted pool of
certificates. A certificate cannot be more secure than the method its CA certificate has been retrieved
with.
This trusted pool of certificates is used by the command verify to ensure that the given S/MIME messages
can be trusted. If so, verified sender certificates that were embedded in signed messages can be saved
locally with the command certsave, and used by S-nail to encrypt further communication with these
senders:
? certsave FILENAME
? set smime-encrypt-USER@HOST=FILENAME \
smime-cipher-USER@HOST=AES256
To sign outgoing messages, in order to allow receivers to verify the origin of these messages, a personal
S/MIME certificate is required. S-nail supports password-protected personal certificates (and keys), see
smime-sign-cert. The section “On URL syntax and credential lookup” gives an overview of the possible
sources of user credentials, and “S/MIME step by step” shows examplarily how a private S/MIME certificate
can be obtained. In general, if such a private key plus certificate “pair” is available, all that needs
to be done is to set some variables:
? set smime-sign-cert=ME@exam.ple.paired \
smime-sign-digest=SHA512 \
smime-sign
Variables of interest for S/MIME in general are smime-ca-dir, smime-ca-file, smime-ca-flags,
smime-ca-no-defaults, smime-crl-dir, smime-crl-file. For S/MIME signing of interest are smime-sign,
smime-sign-cert, smime-sign-include-certs and smime-sign-digest. Additional variables of interest for
S/MIME en- and decryption: smime-cipher and smime-encrypt-USER@HOST. S/MIME is available if ‘+smime’ is
included in features.
[v15 behaviour may differ] Note that neither S/MIME signing nor encryption applies to message subjects or
other header fields yet. Thus they may not contain sensitive information for encrypted messages, and
cannot be trusted even if the message content has been verified. When sending signed messages, it is
recommended to repeat any important header information in the message text.
On URL syntax and credential lookup
[v15-compat] For accessing protocol-specific resources usage of Uniform Resource Locators (URL, RFC 3986)
has become omnipresent. S-nail expects and understands URLs in a “normalized” variant which is not used
in data exchange, but only meant as a compact, easy-to-use way of defining and representing information
in a well-known notation; as such they do not conform to any real standard. Optional parts are placed in
brackets ‘[]’, optional either because there also exist other ways to define the information in question,
or because the part is protocol-specific, e.g., ‘/path’ is used by the [Option]al Maildir file type and
the IMAP protocol, but not by POP3. If as part of the URL any of ‘USER’ and ‘PASSWORD’ is specified,
then the URL percent encoded form must be used (RFC 3986; the command urlcodec can be used to perform the
encoding):
PROTOCOL://[USER[:PASSWORD]@]server[:port][/path]
Many internal variables of S-nail exist in multiple versions, called variable chains for the rest of this
document: the plain ‘variable’ as well as ‘variable-HOST’ and ‘variable-USER@HOST’. Here ‘HOST’ indeed
means ‘server:port’ if a ‘port’ had been specified in the respective URL, otherwise it refers to the
plain ‘server’. Also, ‘USER’ is not truly the ‘USER’ that had been found when doing the user chain
lookup as is described below, i.e., this ‘USER’ will never be in URL percent encoded form, whether it
came from an URL or not; i.e., variable chain name extensions of “INTERNAL VARIABLES” must not be URL
percent encoded.
For example, whether an hypothetical URL ‘smtp://hey%3Ayou@our.house’ had been given that includes a
user, or whether the URL was ‘smtp://our.house’ and the user had been found differently, to lookup the
variable chain smtp-use-starttls S-nail first looks for whether ‘smtp-use-starttls-hey:you@our.house’ is
defined, then whether ‘smtp-use-starttls-our.house’ exists before finally ending up looking at the plain
variable itself.
S-nail obeys the following logic scheme when dealing with the necessary credential information of an
account:
• A user is always required. If no ‘USER’ has been given in the URL the variables user-HOST and user
are looked up. If no such variable(s) can be found then S-nail will, when enforced by the [Option]al
variables netrc-lookup-HOST or netrc-lookup, search “The .netrc file” of the user for a ‘HOST’
specific entry which provides a ‘login’ name: this lookup will only succeed if unambiguous (one
possible matching entry for ‘HOST’).
If there is still no ‘USER’ then S-nail will fall back to the user who is supposed to run S-nail, the
identity of which has been fixated during S-nail startup and is known to be a valid user on the
current host.
• Authentication: unless otherwise noted this will lookup the PROTOCOL-auth-USER@HOST,
PROTOCOL-auth-HOST, PROTOCOL-auth variable chain, falling back to a protocol-specific default should
this have no success.
• If no ‘PASSWORD’ has been given in the URL, then if the ‘USER’ has been found through the [Option]al
netrc-lookup that may have already provided the password, too. Otherwise the variable chain
password-USER@HOST, password-HOST, password is looked up and used if existent.
Afterwards the complete [Option]al variable chain netrc-lookup-USER@HOST, netrc-lookup-HOST,
netrc-lookup is looked up. If set, the netrc cache is searched for a password only (multiple user
accounts for a single machine may exist as well as a fallback entry without user but with a
password).
If at that point there is still no password available, but the (protocols') chosen authentication
type requires a password, then in interactive mode the user will be prompted on the terminal.
Note: S/MIME verification works relative to the values found in the ‘From:’ (or ‘Sender:’) header
field(s), which means that the values of smime-sign, smime-sign-cert, smime-sign-include-certs and
smime-sign-digest will not be looked up using the ‘USER’ and ‘HOST’ chains from above but instead use the
corresponding values from the message that is being worked on. In unusual cases multiple and different
‘USER’ and ‘HOST’ combinations may therefore be involved – on the other hand those unusual cases become
possible. The usual case is as short as:
set mta=smtp://USER:PASS@HOST smtp-use-starttls \
smime-sign smime-sign-cert=+smime.pair
The section “EXAMPLES” contains complete example configurations.
Encrypted network communication
[Option] SSL (Secure Sockets Layer) aka its successor TLS (Transport Layer Security) are protocols which
aid in securing communication by providing a safely initiated and encrypted network connection. A
central concept of TLS is that of certificates: as part of each network connection setup a (set of)
certificates will be exchanged, and by using those the identity of the network peer can be
cryptographically verified; if possible the TLS/SNI (ServerNameIndication) extension will be enabled in
order to allow servers fine-grained control over the certificates being used. TLS works by using a
locally installed pool of trusted certificates, and verifying the connection peer succeeds if that
provides a certificate which has been issued or is trusted by any certificate in the trusted local pool.
The local pool of trusted so-called CA (Certification Authority) certificates is usually delivered with
the used TLS library, and will be selected automatically. It is also possible to use a specific pool of
trusted certificates. If this is desired, tls-ca-no-defaults should be set to avoid using the default
certificate pool, and tls-ca-file and/or (with special preparation) tls-ca-dir should be pointed to a
trusted pool of certificates. A certificate cannot be more secure than the method its CA certificate has
been retrieved with. For inspection or other purposes, the certificate of a server (as seen when
connecting to it) can be fetched like this:
$ </dev/null openssl s_client -showcerts -connect \
the-server.example:pop3s 2>&1 | tee log.txt
S-nail also supports a mode of operation in which certificates are not at all matched against a local
pool of CA certificates. Instead a message digest will be calculated for the certificate presented by
the connection peer, and be compared against tls-fingerprint (a variable chain that picks up ‘USER@HOST’
or ‘HOST’ context-dependent variable variants), and the connection will succeed if the calculated digest
equals the expected one. The used message digest can be configured via (the chain)
tls-fingerprint-digest. The command tls may be helpful.
It depends on the used protocol whether encrypted communication is possible, and which configuration
steps have to be taken to enable it. Some protocols, e.g., POP3S, are implicitly encrypted, others, like
POP3, can upgrade a plain text connection if so requested. For example, to use the ‘STLS’ that POP3
offers (a member of) the variable (chain) pop3-use-starttls needs to be set, with convenience via
shortcut:
shortcut encpop1 pop3s://pop1.exam.ple
shortcut encpop2 pop3://pop2.exam.ple
set pop3-use-starttls-pop2.exam.ple
set mta=smtps://smtp.exam.ple:465
set mta=smtp://smtp.exam.ple smtp-use-starttls
Normally that is all there is to do, given that TLS libraries try to provide safe defaults, plenty of
knobs however exist to adjust settings. For example certificate verification settings can be fine-tuned
via tls-ca-flags, and the TLS configuration basics are accessible via tls-config-pairs, for example to
specify the allowed protocols or cipher lists that a communication channel may use. In the past hints on
how to restrict the set of protocols to highly secure ones were indicated, but as of the time of this
writing the list of protocols or ciphers may need to become relaxed in order to be able to connect to
some servers; the following example allows connecting to a “Lion” that uses OpenSSL 0.9.8za from June
2014 (refer to “INTERNAL VARIABLES” for more on variable chains):
wysh set tls-config-pairs-lion@exam.ple='MinProtocol=TLSv1.1,\
CipherString=TLSv1.2:!aNULL:!eNULL:\
ECDHE-RSA-AES256-SHA:ECDHE-ECDSA-AES256-SHA:\
DHE-RSA-AES256-SHA:@STRENGTH'
The OpenSSL program ciphers(1) can be used and should be referred to when creating a custom cipher list.
Variables of interest for TLS in general are tls-ca-dir, tls-ca-file, tls-ca-flags, tls-ca-no-defaults,
tls-config-file, tls-config-module, tls-config-pairs, tls-crl-dir, tls-crl-file, tls-rand-file as well as
tls-verify. Also see tls-features. TLS is available if ‘+tls’ is included in features.
Character sets
[Option] S-nail detects the character set of the terminal by using mechanisms that are controlled by the
LC_CTYPE environment variable (in fact LC_ALL, LC_CTYPE, LANG, in that order, see there). The internal
variable ttycharset will be set to the detected terminal character set accordingly, and will thus show up
in the output of commands like, e.g., set and varshow.
However, the user may give ttycharset a value during startup, making it possible to send mail in a
completely “faked” locale environment, an option which can be used to generate and send, e.g., 8-bit
UTF-8 input data in a pure 7-bit US-ASCII ‘LC_ALL=C’ environment (an example of this can be found in the
section “On sending mail, and non-interactive mode”). Changing the value does not mean much beside that,
because several aspects of the real character set are implied by the locale environment of the system,
which stays unaffected by ttycharset.
Messages and attachments which consist of 7-bit clean data will be classified as consisting of
charset-7bit character data. This is a problem if the ttycharset character set is a multibyte character
set that is also 7-bit clean. For example, the Japanese character set ISO-2022-JP is 7-bit clean but
capable to encode the rich set of Japanese Kanji, Hiragana and Katakana characters: in order to notify
receivers of this character set the mail message must be MIME encoded so that the character set
ISO-2022-JP can be advertised! To achieve this, the variable charset-7bit must be set to ISO-2022-JP.
(Today a better approach regarding email is the usage of UTF-8, which uses 8-bit bytes for non-US-ASCII
data.)
If the [Option]al character set conversion capabilities are not available (features does not include the
term ‘+iconv’), then ttycharset will be the only supported character set, it is simply assumed that it
can be used to exchange 8-bit messages (over the wire an intermediate, configurable mime-encoding may be
applied), and the rest of this section does not apply; it may however still be necessary to explicitly
set it if automatic detection fails, since in that case it defaults to LATIN1 aka ISO-8859-1 unless the
operating system environment is known to always and exclusively support UTF-8 locales.
[Option] When reading messages, their text is converted into ttycharset as necessary in order to display
them on the user's terminal. Unprintable characters and invalid byte sequences are detected and replaced
by proper substitution characters. Character set mappings for source character sets can be established
with the command charsetalias, which may be handy to work around faulty character set catalogues (e.g.,
to add a missing LATIN1 to ISO-8859-1 mapping), or to enforce treatment of one character set as another
one (e.g., to interpret LATIN1 as CP1252). Also see charset-unknown-8bit to deal with another hairy
aspect of message interpretation.
When sending messages their parts and attachments are classified. Whereas no character set conversion is
performed on those parts which appear to be binary data, the character set being used must be declared
within the MIME header of an outgoing text part if it contains characters that do not conform to the set
of characters that are allowed by the email standards. Permissible values for character sets used in
outgoing messages can be declared using the sendcharsets variable, and charset-8bit, which defines a
catch-all last-resort fallback character set that is implicitly appended to the list of character sets in
sendcharsets.
When replying to a message and the variable reply-in-same-charset is set, then the character set of the
message being replied to is tried first (still being a subject of charsetalias). And it is also possible
to make S-nail work even more closely related to the current locale setting automatically by using the
variable sendcharsets-else-ttycharset, please see there for more information.
All the specified character sets are tried in order unless the conversion of the part or attachment
succeeds. If none of the tried (8-bit) character sets is capable to represent the content of the part or
attachment, then the message will not be send and its text will optionally be saved in DEAD. If that is
not acceptable, the variable mime-force-sendout can be set in order to force sending of non-convertible
text as ‘application/octet-stream’ classified binary content instead; like this receivers still have the
option to inspect message content (for example by setting mime-counter-evidence).
In general, if a message saying “cannot convert from a to b” appears, either some characters are not
appropriate for the currently selected (terminal) character set, or the needed conversion is not
supported by the system. In the first case, it is necessary to set an appropriate LC_CTYPE locale and/or
the variable ttycharset. The best results are usually achieved when S-nail is run in a UTF-8 locale on
an UTF-8 capable terminal, in which case the full Unicode spectrum of characters is available. In this
setup characters from various countries can be displayed, while it is still possible to use more simple
character sets for sending to retain maximum compatibility with older mail clients.
On the other hand the POSIX standard defines a locale-independent 7-bit “portable character set” that
should be used when overall portability is an issue, the even more restricted subset named “portable
filename character set” consists of A-Z, a-z, 0-9, period ‘.’, underscore ‘_’ and hyphen-minus ‘-’.
Message states
S-nail differentiates in between several message states; the current state will be reflected in the
summary of headers if the attrlist of the configured headline allows, and “Specifying messages” dependent
on their state is possible. When operating on the system inbox, or in any other “primary system
mailbox”, special actions, like the automatic moving of messages to the “secondary mailbox” MBOX, may be
applied when the mailbox is left (also implicitly by program termination, unless the command exit was
used) – however, because this may be irritating to users which are used to “more modern” mail-user-
agents, the provided global s-nail.rc template sets the internal hold and keepsave variables in order to
suppress this behaviour.
‘new’ Message has neither been viewed nor moved to any other state. Such messages are retained even
in the “primary system mailbox”.
‘unread’ Message has neither been viewed nor moved to any other state, but the message was present
already when the mailbox has been opened last: Such messages are retained even in the “primary
system mailbox”.
‘read’ The message has been processed by one of the following commands: ~f, ~m, ~F, ~M, copy, mbox,
next, pipe, Print, print, top, Type, type, undelete. The commands dp and dt will always try to
automatically “step” and type the “next” logical message, and may thus mark multiple messages
as read, the delete command will do so if the internal variable autoprint is set.
Except when the exit command is used, messages that are in a “primary system mailbox” and are
in ‘read’ state when the mailbox is left will be saved in the “secondary mailbox” MBOX unless
the internal variable hold it set.
‘deleted’ The message has been processed by one of the following commands: delete, dp, dt. Only undelete
can be used to access such messages.
‘preserved’ The message has been processed by a preserve command and it will be retained in its current
location.
‘saved’ The message has been processed by one of the following commands: save or write. Unless when
the exit command is used, messages that are in a “primary system mailbox” and are in ‘saved’
state when the mailbox is left will be deleted; they will be saved in the “secondary mailbox”
MBOX when the internal variable keepsave is set.
In addition to these message states, flags which otherwise have no technical meaning in the mail system
except allowing special ways of addressing them when “Specifying messages” can be set on messages. These
flags are saved with messages and are thus persistent, and are portable between a set of widely used
MUAs.
answered Mark messages as having been answered.
draft Mark messages as being a draft.
flag Mark messages which need special attention.
Specifying messages
[Only new quoting rules] Commands which take “Message list arguments”, such as from aka search, type and
delete, can be given a list of message numbers as arguments to apply to a number of messages at once.
Thus ‘delete 1 2’ deletes messages 1 and 2, whereas ‘delete 1-5’ will delete the messages 1 through 5.
In sorted or threaded mode (see the sort command), ‘delete 1-5’ will delete the messages that are located
between (and including) messages 1 through 5 in the sorted/threaded order, as shown in the headers
summary. The following special message names exist:
. The current message, the so-called “dot”.
; The message that was previously the current message; needs to be quoted.
, The parent message of the current message, that is the message with the Message-ID given in the
‘In-Reply-To:’ field or the last entry of the ‘References:’ field of the current message.
- The previous undeleted message, or the previous deleted message for the undelete command; In
sorted or ‘thread’ed mode, the previous such message in the according order.
+ The next undeleted message, or the next deleted message for the undelete command; In sorted or
‘thread’ed mode, the next such message in the according order.
^ The first undeleted message, or the first deleted message for the undelete command; In sorted
or ‘thread’ed mode, the first such message in the according order.
$ The last message; In sorted or ‘thread’ed mode, the last such message in the according order.
Needs to be quoted.
&x In ‘thread’ed sort mode, selects the message addressed with x, where x is any other message
specification, and all messages from the thread that begins at it. Otherwise it is identical
to x. If x is omitted, the thread beginning with the current message is selected.
* All messages.
` All messages that were included in the “Message list arguments” of the previous command; needs
to be quoted.
x-y An inclusive range of message numbers. Selectors that may also be used as endpoints include
any of .;-+^$.
address A case-insensitive “any substring matches” search against the ‘From:’ header, which will match
addresses (too) even if showname is set (and POSIX says “any address as shown in a header
summary shall be matchable in this form”); However, if the allnet variable is set, only the
local part of the address is evaluated for the comparison, not ignoring case, and the setting
of showname is completely ignored. For finer control and match boundaries use the ‘@’ search
expression.
/string All messages that contain string in the subject field (case ignored according to locale). See
also the searchheaders variable. If string is empty, the string from the previous
specification of that type is used again.
[@name-list]@expr
All messages that contain the given case-insensitive search expression; If the [Option]al
regular expression support is available expr will be interpreted as (an extended) one if any of
the “magic regular expression characters” is seen. If the optional @name-list part is missing
the search is restricted to the subject field body, but otherwise name-list specifies a comma-
separated list of header fields to search, e.g.,
'@to,from,cc@Someone i ought to know'
In order to search for a string that includes a ‘@’ (commercial at) character the name-list is
effectively non-optional, but may be given as the empty string. Also, specifying an empty
search expression will effectively test for existence of the given header fields. Some special
header fields may be abbreviated: ‘f’, ‘t’, ‘c’, ‘b’ and ‘s’ will match ‘From’, ‘To’, ‘Cc’,
‘Bcc’ and ‘Subject’, respectively and case-insensitively. [Option]ally, and just like expr,
name-list will be interpreted as (an extended) regular expression if any of the “magic regular
expression characters” is seen.
The special names ‘header’ or ‘<’ can be used to search in (all of) the header(s) of the
message, and the special names ‘body’ or ‘>’ and ‘text’ or ‘=’ will perform full text searches
– whereas the former searches only the body, the latter also searches the message header ([v15
behaviour may differ] this mode yet brute force searches over the entire decoded content of
messages, including administrativa strings).
This specification performs full text comparison, but even with regular expression support it
is almost impossible to write a search expression that safely matches only a specific address
domain. To request that the body content of the header is treated as a list of addresses, and
to strip those down to the plain email address which the search expression is to be matched
against, prefix the effective name-list with a tilde ‘~’:
'@~f,c@@a\.safe\.domain\.match$'
:c All messages of state or with matching condition ‘c’, where ‘c’ is one or multiple of the
following colon modifiers:
a answered messages (cf. the variable markanswered).
d ‘deleted’ messages (for the undelete and from commands only).
f flagged messages.
L Messages with receivers that match mlsubscribed addresses.
l Messages with receivers that match mlisted addresses.
n ‘new’ messages.
o Old messages (any not in state ‘read’ or ‘new’).
r ‘read’ messages.
S [Option] Messages with unsure spam classification (see “Handling spam”).
s [Option] Messages classified as spam.
t Messages marked as draft.
u ‘unread’ messages.
[Option] IMAP-style SEARCH expressions may also be used. These consist of keywords and criterions, and
because “Message list arguments” are split into tokens according to “Shell-style argument quoting” it is
necessary to quote the entire IMAP search expression in order to ensure that it remains a single token.
This addressing mode is available with all types of mailbox folders; S-nail will perform the search
locally as necessary. Strings must be enclosed by double quotes ‘"’ in their entirety if they contain
whitespace or parentheses; within the quotes, only reverse solidus ‘\’ is recognized as an escape
character. All string searches are case-insensitive. When the description indicates that the “envelope”
representation of an address field is used, this means that the search string is checked against both a
list constructed as
'("name" "source" "local-part" "domain-part")'
for each address, and the addresses without real names from the respective header field. These search
expressions can be nested using parentheses, see below for examples.
(criterion)
All messages that satisfy the given criterion.
(criterion1 criterion2 ... criterionN)
All messages that satisfy all of the given criteria.
(or criterion1 criterion2)
All messages that satisfy either criterion1 or criterion2, or both. To connect more than two
criteria using ‘or’ specifications have to be nested using additional parentheses, as with ‘(or
a (or b c))’, since ‘(or a b c)’ really means ‘((a or b) and c)’. For a simple ‘or’ operation
of independent criteria on the lowest nesting level, it is possible to achieve similar effects
by using three separate criteria, as with ‘(a) (b) (c)’.
(not criterion)
All messages that do not satisfy criterion.
(bcc "string")
All messages that contain string in the envelope representation of the ‘Bcc:’ field.
(cc "string")
All messages that contain string in the envelope representation of the ‘Cc:’ field.
(from "string")
All messages that contain string in the envelope representation of the ‘From:’ field.
(subject "string")
All messages that contain string in the ‘Subject:’ field.
(to "string")
All messages that contain string in the envelope representation of the ‘To:’ field.
(header name "string")
All messages that contain string in the specified ‘Name:’ field.
(body "string")
All messages that contain string in their body.
(text "string")
All messages that contain string in their header or body.
(larger size)
All messages that are larger than size (in bytes).
(smaller size)
All messages that are smaller than size (in bytes).
(before date)
All messages that were received before date, which must be in the form ‘d[d]-mon-yyyy’, where
‘d’ denotes the day of the month as one or two digits, ‘mon’ is the name of the month – one of
‘Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec’, and ‘yyyy’ is the year as four digits, e.g.,
‘28-Dec-2012’.
(on date)
All messages that were received on the specified date.
(since date)
All messages that were received since the specified date.
(sentbefore date)
All messages that were sent on the specified date.
(senton date)
All messages that were sent on the specified date.
(sentsince date)
All messages that were sent since the specified date.
() The same criterion as for the previous search. This specification cannot be used as part of
another criterion. If the previous command line contained more than one independent criterion
then the last of those criteria is used.
On terminal control and line editor
[Option] Terminal control will be realized through one of the standard Unix libraries, either the Termcap
Access Library (libtermcap, -ltermcap), or, alternatively, the Terminal Information Library (libterminfo,
-lterminfo), both of which will be initialized to work with the environment variable TERM. Terminal
control will enhance or enable interactive usage aspects, e.g., “Coloured display”, and extend behaviour
of the Mailx-Line-Editor (MLE), which may learn the byte-sequences of keys like the cursor- and function-
keys.
The internal variable termcap can be used to overwrite settings or to learn (correct(ed)) keycodes.
Actual library interaction can be disabled completely by setting termcap-disable; termcap will be queried
regardless, which is true even if the [Option]al library support has not been enabled at configuration
time as long as some other [Option] which (may) query terminal control sequences has been enabled.
S-nail can be told to enter an alternative exclusive screen, the so-called ca-mode, by setting
termcap-ca-mode; this requires sufficient terminal support, and the used PAGER may also need special
configuration, dependent on the value of crt.
[Option] The built-in Mailx-Line-Editor (MLE) should work in all environments which comply to the ISO C
standard ISO/IEC 9899/AMD1:1995 (“ISO C90, Amendment 1”), and will support wide glyphs if possible (the
necessary functionality had been removed from ISO C, but was included in X/Open Portability Guide Issue 4
(“XPG4”)). Usage of a line editor in interactive mode can be prevented by setting line-editor-disable.
Especially if the [Option]al terminal control support is missing setting entries in the internal variable
termcap will help shall the MLE misbehave, see there for more. The MLE can support a little bit of
colour.
[Option] If the history feature is available then input from line editor prompts will be saved in a
history list that can be searched in and be expanded from. Such saving can be prevented by prefixing
input with any amount of whitespace. Aspects of history, like allowed content and maximum size, as well
as whether history shall be saved persistently, can be configured with the internal variables
history-file, history-gabby, history-gabby-persist and history-size. There also exists the macro hook
on-history-addition which can be used to apply fine control on what enters history.
The MLE supports a set of editing and control commands. By default (as) many (as possible) of these will
be assigned to a set of single-letter control codes, which should work on any terminal (and can be
generated by holding the “control” key while pressing the key of desire, e.g., ‘control-D’). If the
[Option]al bind command is available then the MLE commands can also be accessed freely by assigning the
command name, which is shown in parenthesis in the list below, to any desired key-sequence, and the MLE
will instead and also use bind to establish its built-in key bindings (more of them if the [Option]al
terminal control is available), an action which can then be suppressed completely by setting
line-editor-no-defaults. “Shell-style argument quoting” notation is used in the following; combinations
not mentioned either cause job control signals or do not generate a (unique) keycode:
‘\cA’ Go to the start of the line (mle-go-home).
‘\cB’ Move the cursor backward one character (mle-go-bwd).
‘\cC’ raise(3) ‘SIGINT’ (mle-raise-int).
‘\cD’ Forward delete the character under the cursor; quits S-nail if used on the empty line unless
the internal variable ignoreeof is set (mle-del-fwd).
‘\cE’ Go to the end of the line (mle-go-end).
‘\cF’ Move the cursor forward one character (mle-go-fwd).
‘\cG’ Cancel current operation, full reset. If there is an active history search or tabulator
expansion then this command will first reset that, reverting to the former line content; thus a
second reset is needed for a full reset in this case (mle-reset).
‘\cH’ Backspace: backward delete one character (mle-del-bwd).
‘\cI’ [Only new quoting rules] Horizontal tabulator: try to expand the word before the cursor,
supporting the usual “Filename transformations” (mle-complete; this is affected by
mle-quote-rndtrip and line-editor-cpl-word-breaks).
‘\cJ’ Newline: commit the current line (mle-commit).
‘\cK’ Cut all characters from the cursor to the end of the line (mle-snarf-end).
‘\cL’ Repaint the line (mle-repaint).
‘\cN’ [Option] Go to the next history entry (mle-hist-fwd).
‘\cO’ ([Option]ally context-dependent) Invokes the command dt.
‘\cP’ [Option] Go to the previous history entry (mle-hist-bwd).
‘\cQ’ Toggle roundtrip mode shell quotes, where produced, on and off (mle-quote-rndtrip). This
setting is temporary, and will be forgotten once the command line is committed; also see
shcodec.
‘\cR’ [Option] Complete the current line from (the remaining) older history entries
(mle-hist-srch-bwd).
‘\cS’ [Option] Complete the current line from (the remaining) newer history entries
(mle-hist-srch-fwd).
‘\cT’ Paste the snarf buffer (mle-paste).
‘\cU’ The same as ‘\cA’ followed by ‘\cK’ (mle-snarf-line).
‘\cV’ Prompts for a Unicode character (hexadecimal number without prefix, see vexpr) to be inserted
(mle-prompt-char). Note this command needs to be assigned to a single-letter control code in
order to become recognized and executed during input of a key-sequence (only three single-
letter control codes can be used for that shortcut purpose); this control code is then special-
treated and thus cannot be part of any other sequence (because it will trigger the
mle-prompt-char function immediately).
‘\cW’ Cut the characters from the one preceding the cursor to the preceding word boundary
(mle-snarf-word-bwd).
‘\cX’ Move the cursor forward one word boundary (mle-go-word-fwd).
‘\cY’ Move the cursor backward one word boundary (mle-go-word-bwd).
‘\cZ’ raise(3) ‘SIGTSTP’ (mle-raise-tstp).
‘\c[’ Escape: reset a possibly used multibyte character input state machine and [Option]ally a
lingering, incomplete key binding (mle-cancel). This command needs to be assigned to a single-
letter control code in order to become recognized and executed during input of a key-sequence
(only three single-letter control codes can be used for that shortcut purpose). This control
code may also be part of a multi-byte sequence, but if a sequence is active and the very
control code is currently also an expected input, then the active sequence takes precedence and
will consume the control code.
‘\c\’ ([Option]ally context-dependent) Invokes the command ‘z+’.
‘\c]’ ([Option]ally context-dependent) Invokes the command ‘z$’.
‘\c^’ ([Option]ally context-dependent) Invokes the command ‘z0’.
‘\c_’ Cut the characters from the one after the cursor to the succeeding word boundary
(mle-snarf-word-fwd).
‘\c?’ Backspace: mle-del-bwd.
– mle-bell: ring the audible bell.
– [Option] mle-clear-screen: move the cursor home and clear the screen.
– mle-fullreset: different to mle-reset this will immediately reset a possibly active search etc.
– mle-go-screen-bwd: move the cursor backward one screen width.
– mle-go-screen-fwd: move the cursor forward one screen width.
– mle-raise-quit: raise(3) ‘SIGQUIT’.
Coloured display
[Option] S-nail can be configured to support a coloured display and font attributes by emitting ANSI aka
ISO 6429 SGR (select graphic rendition) escape sequences. Usage of colours and font attributes solely
depends upon the capability of the detected terminal type that is defined by the environment variable
TERM and which can be fine-tuned by the user via the internal variable termcap.
On top of what S-nail knows about the terminal the boolean variable colour-pager defines whether the
actually applicable colour and font attribute sequences should also be generated when output is going to
be paged through the external program defined by the environment variable PAGER (also see crt). This is
not enabled by default because different pager programs need different command line switches or other
configuration in order to support those sequences. S-nail however knows about some widely used pagers
and in a clean environment it is often enough to simply set colour-pager; please refer to that variable
for more on this topic.
Colours and font attributes can be managed with the multiplexer command colour, and uncolour can be used
to remove mappings of a given colour type. If the variable colour-disable is set then any active usage
of colour and font attribute sequences is suppressed without affecting possibly established colour
mappings. Since colours are available if any of the standard I/O descriptors it opened on a terminal, it
might make sense to conditionalize the colour setup by encapsulating it with if (‘terminal’ indeed means
“interactive”):
if terminal && [ "$features" =% +colour ]
colour iso view-msginfo ft=bold,fg=green
colour iso view-header ft=bold,fg=red (from|subject) # regex
colour iso view-header fg=red
uncolour iso view-header from,subject
colour iso view-header ft=bold,fg=magenta,bg=cyan
colour 256 view-header ft=bold,fg=208,bg=230 "subject,from"
colour mono view-header ft=bold
colour mono view-header ft=bold,ft=reverse subject,from
endif
Handling spam
[Option] S-nail can make use of several spam interfaces for the purpose of identification of, and, in
general, dealing with spam messages. A precondition of most commands in order to function is that the
spam-interface variable is set to one of the supported interfaces. “Specifying messages” that have been
identified as spam is possible via their (volatile) ‘is-spam’ state by using the ‘:s’ and ‘:S’
specifications, and their attrlist entries will be used when displaying the headline in the summary of
headers.
• spamrate rates the given messages and sets their ‘is-spam’ flag accordingly. If the spam interface
offers spam scores these can be shown in headline by using the format ‘%$’.
• spamham, spamspam and spamforget will interact with the Bayesian filter of the chosen interface and
learn the given messages as “ham” or “spam”, respectively; the last command can be used to cause
“unlearning” of messages; it adheres to their current ‘is-spam’ state and thus reverts previous
teachings.
• spamclear and spamset will simply set and clear, respectively, the mentioned volatile ‘is-spam’
message flag, without any interface interaction.
The spamassassin(1) based spam-interface ‘spamc’ requires a running instance of the spamd(1) server in
order to function, started with the option --allow-tell shall Bayesian filter learning be possible.
$ spamd -i localhost:2142 -i /tmp/.spamsock -d [-L] [-l]
$ spamd --listen=localhost:2142 --listen=/tmp/.spamsock \
--daemonize [--local] [--allow-tell]
Thereafter S-nail can make use of these interfaces:
$ s-nail -Sspam-interface=spamc -Sspam-maxsize=500000 \
-Sspamc-command=/usr/local/bin/spamc \
-Sspamc-arguments="-U /tmp/.spamsock" -Sspamc-user=
or
$ s-nail -Sspam-interface=spamc -Sspam-maxsize=500000 \
-Sspamc-command=/usr/local/bin/spamc \
-Sspamc-arguments="-d localhost -p 2142" -Sspamc-user=
Using the generic filter approach allows usage of programs like bogofilter(1). Here is an example,
requiring it to be accessible via PATH:
$ s-nail -Sspam-interface=filter -Sspam-maxsize=500000 \
-Sspamfilter-ham="bogofilter -n" \
-Sspamfilter-noham="bogofilter -N" \
-Sspamfilter-nospam="bogofilter -S" \
-Sspamfilter-rate="bogofilter -TTu 2>/dev/null" \
-Sspamfilter-spam="bogofilter -s" \
-Sspamfilter-rate-scanscore="1;^(.+)$"
Because messages must exist on local storage in order to be scored (or used for Bayesian filter
training), it is possibly a good idea to perform the local spam check last. Spam can be checked
automatically when opening specific folders by setting a specialized form of the internal variable
folder-hook.
define spamdelhook {
# Server side DCC
spamset (header x-dcc-brand-metrics "bulk")
# Server-side spamassassin(1)
spamset (header x-spam-flag "YES")
del :s # TODO we HAVE to be able to do `spamrate :u ! :sS'
move :S +maybe-spam
spamrate :u
del :s
move :S +maybe-spam
}
set folder-hook-SOMEFOLDER=spamdelhook
See also the documentation for the variables spam-interface, spam-maxsize, spamc-command,
spamc-arguments, spamc-user, spamfilter-ham, spamfilter-noham, spamfilter-nospam, spamfilter-rate and
spamfilter-rate-scanscore.
COMMANDS
S-nail reads input in lines. An unquoted reverse solidus ‘\’ at the end of a command line “escapes” the
newline character: it is discarded and the next line of input is used as a follow-up line, with all
leading whitespace removed; once an entire line is completed, the whitespace characters space, tabulator,
newline as well as those defined by the variable ifs are removed from the beginning and end. Placing any
whitespace characters at the beginning of a line will prevent a possible addition of the command line to
the [Option]al history.
The beginning of such input lines is then scanned for the name of a known command: command names may be
abbreviated, in which case the first command that matches the given prefix will be used. “Command
modifiers” may prefix a command in order to modify its behaviour. A name may also be a commandalias,
which will become expanded until no more expansion is possible. Once the command that shall be executed
is known, the remains of the input line will be interpreted according to command-specific rules,
documented in the following.
This behaviour is different to the sh(1)ell, which is a programming language with syntactic elements of
clearly defined semantics, and therefore capable to sequentially expand and evaluate individual elements
of a line. S-nail will never be able to handle ‘? set one=value two=$one’ in a single statement, because
the variable assignment is performed by the command (set), not the language.
The command list can be used to show the list of all commands, either alphabetically sorted or in prefix
search order (these do not match, also because the POSIX standard prescribes a set of abbreviations).
[Option]ally the command help (or ?), when given an argument, will show a documentation string for the
command matching the expanded argument, as in ‘?t’, which should be a shorthand of ‘?type’; with these
documentation strings both commands support a more verbose listing mode which includes the argument type
of the command and other information which applies; a handy suggestion might thus be:
? define __xv {
# Before v15: need to enable sh(1)ell-style on _entire_ line!
localopts yes;wysh set verbose;ignerr eval "${@}";return ${?}
}
? commandalias xv '\call __xv'
? xv help set
Command modifiers
Commands may be prefixed by one or multiple command modifiers. Some command modifiers can be used with a
restricted set of commands only, the verbose version of list will ([Option]ally) show which modifiers
apply.
• The modifier reverse solidus \, to be placed first, prevents commandalias expansions on the remains
of the line, e.g., ‘\echo’ will always evaluate the command echo, even if an (command)alias of the
same name exists. commandalias content may itself contain further command modifiers, including an
initial reverse solidus to prevent further expansions.
• The modifier ignerr indicates that any error generated by the following command should be ignored by
the state machine and not cause a program exit with enabled errexit or for the standardized exit
cases in posix mode. ?, one of the “INTERNAL VARIABLES”, will be set to the real exit status of the
command regardless.
• local will alter the called command to apply changes only temporarily, local to block-scope, and can
thus only be used inside of a defined macro or an account definition. Specifying it implies the
modifier wysh. Block-scope settings will not be inherited by macros deeper in the call chain, and
will be garbage collected once the current block is left. To record and unroll changes in the global
scope use the command localopts.
• scope does yet not implement any functionality.
• u does yet not implement any functionality.
• Some commands support the vput modifier: if used, they expect the name of a variable, which can
itself be a variable, i.e., shell expansion is applied, as their first argument, and will place their
computation result in it instead of the default location (it is usually written to standard output).
The given name will be tested for being a valid sh(1) variable name, and may therefore only consist
of upper- and lowercase characters, digits, and the underscore; the hyphen-minus may be used as a
non-portable extension; digits may not be used as first, hyphen-minus may not be used as last
characters. In addition the name may either not be one of the known “INTERNAL VARIABLES”, or must
otherwise refer to a writable (non-boolean) value variable. The actual put operation may fail
nonetheless, e.g., if the variable expects a number argument only a number will be accepted. Any
error during these operations causes the command as such to fail, and the error number ! will be set
to ^ERR-NOTSUP, the exit status ? should be set to ‘-1’, but some commands deviate from the latter,
which is documented.
• Last, but not least, the modifier wysh can be used for some old and established commands to choose
the new “Shell-style argument quoting” rules over the traditional “Old-style argument quoting”. This
modifier is implied if v15-compat is set to a non-empty value.
Old-style argument quoting
[v15 behaviour may differ] This section documents the old, traditional style of quoting non-message-list
arguments to commands which expect this type of arguments: whereas still used by the majority of such
commands, the new “Shell-style argument quoting” may be available even for those via wysh, one of the
“Command modifiers”. Nonetheless care must be taken, because only new commands have been designed with
all the capabilities of the new quoting rules in mind, which can, e.g., generate control characters.
• An argument can be enclosed between paired double-quotes ‘"argument"’ or single-quotes
‘'argument'’; any whitespace, shell word expansion, or reverse solidus characters (except as
described next) within the quotes are treated literally as part of the argument. A double-
quote will be treated literally within single-quotes and vice versa. Inside such a quoted
string the actually used quote character can be used nonetheless by escaping it with a reverse
solidus ‘\’, as in ‘"y\"ou"’.
• An argument that is not enclosed in quotes, as above, can usually still contain space
characters if those spaces are reverse solidus escaped, as in ‘you\ are’.
• A reverse solidus outside of the enclosing quotes is discarded and the following character is
treated literally as part of the argument.
Shell-style argument quoting
sh(1)ell-style, and therefore POSIX standardized, argument parsing and quoting rules are used by most
commands. [v15 behaviour may differ] Most new commands only support these new rules and are flagged
[Only new quoting rules], some elder ones can use them with the command modifier wysh; in the future only
this type of argument quoting will remain.
A command line is parsed from left to right and an input token is completed whenever an unquoted,
otherwise ignored, metacharacter is seen. Metacharacters are vertical bar |, ampersand &, semicolon ;,
as well as all characters from the variable ifs, and / or space, tabulator, newline. The additional
metacharacters left and right parenthesis (, ) and less-than and greater-than signs <, > that the sh(1)
supports are not used, and are treated as ordinary characters: for one these characters are a vivid part
of email addresses, and it seems highly unlikely that their function will become meaningful to S-nail.
Compatibility note: [v15 behaviour may differ] Please note that even many new-style commands do not
yet honour ifs to parse their arguments: whereas the sh(1)ell is a language with syntactic elements
of clearly defined semantics, S-nail parses entire input lines and decides on a per-command base
what to do with the rest of the line. This also means that whenever an unknown command is seen all
that S-nail can do is cancellation of the processing of the remains of the line.
It also often depends on an actual subcommand of a multiplexer command how the rest of the line
should be treated, and until v15 we are not capable to perform this deep inspection of arguments.
Nonetheless, at least the following commands which work with positional parameters fully support
ifs for an almost shell-compatible field splitting: call, call_if, read, vpospar, xcall.
Any unquoted number sign ‘#’ at the beginning of a new token starts a comment that extends to the end of
the line, and therefore ends argument processing. An unquoted dollar sign ‘$’ will cause variable
expansion of the given name, which must be a valid sh(1)ell-style variable name (see vput): “INTERNAL
VARIABLES” as well as “ENVIRONMENT” (shell) variables can be accessed through this mechanism, brace
enclosing the name is supported (i.e., to subdivide a token).
Whereas the metacharacters space, tabulator, newline only complete an input token, vertical bar |,
ampersand & and semicolon ; also act as control operators and perform control functions. For now
supported is semicolon ;, which terminates a single command, therefore sequencing the command line and
making the remainder of the line a subject to reevaluation. With sequencing, multiple command argument
types and quoting rules may therefore apply to a single line, which can become problematic before v15:
e.g., the first of the following will cause surprising results.
? echo one; set verbose; echo verbose=$verbose.
? echo one; wysh set verbose; echo verbose=$verbose.
Quoting is a mechanism that will remove the special meaning of metacharacters and reserved words, and
will prevent expansion. There are four quoting mechanisms: the escape character, single-quotes, double-
quotes and dollar-single-quotes:
• The literal value of any character can be preserved by preceding it with the escape character
reverse solidus ‘\’.
• Arguments which are enclosed in ‘'single-quotes'’ retain their literal value. A single-quote
cannot occur within single-quotes.
• The literal value of all characters enclosed in ‘"double-quotes"’ is retained, with the
exception of dollar sign ‘$’, which will cause variable expansion, as above, backquote (grave
accent) ‘`’, (which not yet means anything special), reverse solidus ‘\’, which will escape any
of the characters dollar sign ‘$’ (to prevent variable expansion), backquote (grave accent)
‘`’, double-quote ‘"’ (to prevent ending the quote) and reverse solidus ‘\’ (to prevent
escaping, i.e., to embed a reverse solidus character as-is), but has no special meaning
otherwise.
• Arguments enclosed in ‘$'dollar-single-quotes'’ extend normal single quotes in that reverse
solidus escape sequences are expanded as follows:
‘\a’ bell control character (ASCII and ISO-10646 BEL).
‘\b’ backspace control character (ASCII and ISO-10646 BS).
‘\E’ escape control character (ASCII and ISO-10646 ESC).
‘\e’ the same.
‘\f’ form feed control character (ASCII and ISO-10646 FF).
‘\n’ line feed control character (ASCII and ISO-10646 LF).
‘\r’ carriage return control character (ASCII and ISO-10646 CR).
‘\t’ horizontal tabulator control character (ASCII and ISO-10646 HT).
‘\v’ vertical tabulator control character (ASCII and ISO-10646 VT).
‘\\’ emits a reverse solidus character.
‘\'’ single quote.
‘\"’ double quote (escaping is optional).
‘\NNN’ eight-bit byte with the octal value ‘NNN’ (one to three octal digits), optionally
prefixed by an additional ‘0’. A 0 byte will suppress further output for the quoted
argument.
‘\xHH’ eight-bit byte with the hexadecimal value ‘HH’ (one or two hexadecimal characters, no
prefix, see vexpr). A 0 byte will suppress further output for the quoted argument.
‘\UHHHHHHHH’
the Unicode / ISO-10646 character with the hexadecimal codepoint value ‘HHHHHHHH’ (one
to eight hexadecimal characters) — note that Unicode defines the maximum codepoint ever
to be supported as ‘0x10FFFF’ (in planes of ‘0xFFFF’ characters each). This escape is
only supported in locales that support Unicode (see “Character sets”), in other cases
the sequence will remain unexpanded unless the given code point is ASCII compatible or
(if the [Option]al character set conversion is available) can be represented in the
current locale. The character NUL will suppress further output for the quoted
argument.
‘\uHHHH’
Identical to ‘\UHHHHHHHH’ except it takes only one to four hexadecimal characters.
‘\cX’ Emits the non-printable (ASCII and compatible) C0 control codes 0 (NUL) to 31 (US), and
127 (DEL). Printable representations of ASCII control codes can be created by mapping
them to a different, visible part of the ASCII character set. Adding the number 64
achieves this for the codes 0 to 31, e.g., 7 (BEL): ‘7 + 64 = 71 = G’. The real
operation is a bitwise logical XOR with 64 (bit 7 set, see vexpr), thus also covering
code 127 (DEL), which is mapped to 63 (question mark): ‘? vexpr ^ 127 64’.
Whereas historically circumflex notation has often been used for visualization purposes
of control codes, e.g., ‘^G’, the reverse solidus notation has been standardized:
‘\cG’. Some control codes also have standardized (ISO-10646, ISO C) aliases, as shown
above (e.g., ‘\a’, ‘\n’, ‘\t’): whenever such an alias exists it will be used for
display purposes. The control code NUL (‘\c@’, a non-standard extension) will suppress
further output for the remains of the token (which may extend beyond the current
quote), or, depending on the context, the remains of all arguments for the current
command.
‘\$NAME’
Non-standard extension: expand the given variable name, as above. Brace enclosing the
name is supported.
‘\`{command}’
Not yet supported, just to raise awareness: Non-standard extension.
Caveats:
? echo 'Quotes '${HOME}' and 'tokens" differ!"# no comment
? echo Quotes ${HOME} and tokens differ! # comment
? echo Don"'"t you worry$'\x21' The sun shines on us. $'\u263A'
Message list arguments
Many commands operate on message list specifications, as documented in “Specifying messages”. The
argument input is first split into individual tokens via “Shell-style argument quoting”, which are then
interpreted as the mentioned specifications. If no explicit message list has been specified, many
commands will search for and use the next message forward that satisfies the commands' requirements, and
if there are no messages forward of the current message, the search proceeds backwards; if there are no
good messages at all to be found, an error message is shown and the command is aborted. The verbose
output of the command list will indicate whether a command searches for a default message, or not.
Raw data arguments for codec commands
A special set of commands, which all have the string “codec” in their name, e.g., addrcodec, shcodec,
urlcodec, take raw string data as input, which means that the content of the command input line is passed
completely unexpanded and otherwise unchanged: like this the effect of the actual codec is visible
without any noise of possible shell quoting rules etc., i.e., the user can input one-to-one the desired
or questionable data. To gain a level of expansion, the entire command line can be evaluated first,
e.g.,
? vput shcodec res encode /usr/Schönes Wetter/heute.txt
? echo $res
$'/usr/Sch\u00F6nes Wetter/heute.txt'
? shcodec d $res
$'/usr/Sch\u00F6nes Wetter/heute.txt'
? eval shcodec d $res
/usr/Schönes Wetter/heute.txt
Filename transformations
Filenames, where expected, and unless documented otherwise, are subsequently subject to the following
filename transformations, in sequence:
• If the given name is a registered shortcut, it will be replaced with the expanded shortcut.
• The filename is matched against the following patterns or strings:
# (Number sign) is expanded to the previous file.
% (Percent sign) is replaced by the invoking user's primary system mailbox, which either
is the (itself expandable) inbox if that is set, the standardized absolute pathname
indicated by MAIL if that is set, or a built-in compile-time default otherwise.
%user Expands to the primary system mailbox of user (and never the value of inbox, regardless
of its actual setting).
& (Ampersand) is replaced with the invoking user's secondary mailbox, the MBOX.
+file Refers to a file in the folder directory (if that variable is set).
%:filespec Expands to the same value as filespec, but has special meaning when used with, e.g.,
the command file: the file will be treated as a primary system mailbox by, e.g., the
mbox and save commands, meaning that messages that have been read in the current session
will be moved to the MBOX mailbox instead of simply being flagged as read.
• Meta expansions may be applied to the resulting filename, as allowed by the operation and
applicable to the resulting access protocol (also see “On URL syntax and credential lookup”).
For the file-protocol, a leading tilde ‘~’ character will be replaced by the expansion of HOME,
except when followed by a valid user name, in which case the home directory of the given user
is used instead.
A shell expansion as if specified in double-quotes (see “Shell-style argument quoting”) may be
applied, so that any occurrence of ‘$VARIABLE’ (or ‘${VARIABLE}’) will be replaced by the
expansion of the variable, if possible; “INTERNAL VARIABLES” as well as “ENVIRONMENT” (shell)
variables can be accessed through this mechanism.
Shell pathname wildcard pattern expansions (glob(7)) may be applied as documented. If the
fully expanded filename results in multiple pathnames and the command is expecting only one
file, an error results.
In interactive context, in order to allow simple value acceptance (via “ENTER”), arguments will
usually be displayed in a properly quoted form, e.g., a file ‘diet\ is \curd.txt’ may be
displayed as ‘'diet\ is \curd.txt'’.
Commands
The following commands are available:
! Executes the SHELL command which follows, replacing unescaped exclamation marks with the
previously executed command if the internal variable bang is set. This command supports vput
as documented in “Command modifiers”, and manages the error number !. A 0 or positive exit
status ? reflects the exit status of the command, negative ones that an error happened before
the command was executed, or that the program did not exit cleanly, but, e.g., due to a signal:
the error number is ^ERR-CHILD, then.
In conjunction with the vput modifier the following special cases exist: a negative exit status
occurs if the collected data could not be stored in the given variable, which is a ^ERR-NOTSUP
error that should otherwise not occur. ^ERR-CANCELED indicates that no temporary file could be
created to collect the command output at first glance. In case of catchable out-of-memory
situations ^ERR-NOMEM will occur and S-nail will try to store the empty string, just like with
all other detected error conditions.
# The comment-command causes the entire line to be ignored. Note: this really is a normal
command which' purpose is to discard its arguments, not a “comment-start” indicating special
character, which means that, e.g., trailing comments on a line are not possible (except for
commands which use “Shell-style argument quoting”).
+ Goes to the next message in sequence and types it (like “ENTER”).
- Display the preceding message, or the n'th previous message if given a numeric argument n.
= Shows the message number of the current message (the “dot”) when used without arguments, that
of the given list otherwise. Output numbers will be separated from each other with the first
character of ifs, and followed by the first character of if-ws, if that is not empty and not
identical to the first. If that results in no separation at all a space character is used.
This command supports vput (see “Command modifiers”), and manages the error number !.
? [Option] Show a brief summary of commands. [Option] Given an argument a synopsis for the
command in question is shown instead; commands can be abbreviated in general and this command
can be used to see the full expansion of an abbreviation including the synopsis, try, e.g.,
‘?h’, ‘?hel’ and ‘?help’ and see how the output changes. This mode also supports a more
verbose output, which will provide the information documented for list.
| A synonym for the pipe command.
account, unaccount
(ac, una) Creates, selects or lists (an) account(s). Accounts are special incarnations of
defined macros and group commands and variable settings which together usually arrange the
environment for the purpose of creating an email account. Different to normal macros settings
which are covered by localopts – here by default enabled! – will not be reverted before the
account is changed again. The special account ‘null’ (case-insensitive) always exists, and all
but it can be deleted by the latter command, and in one operation with the special name ‘*’.
Also for all but it a possibly set on-account-cleanup hook is called once they are left,
including program exit.
Without arguments a listing of all defined accounts is shown. With one argument the given
account is activated: the system inbox of that account will be activated (as via file), a
possibly installed folder-hook will be run, and the internal variable account will be updated.
The two argument form is identical to defining a macro as via define:
account myisp {
set folder=~/mail inbox=+syste.mbox record=+sent.mbox
set from='(My Name) myname@myisp.example'
set mta=smtp://mylogin@smtp.myisp.example
}
addrcodec
Perform email address codec transformations on raw-data argument, rather according to email
standards (RFC 5322; [v15 behaviour may differ] will furtherly improve). Supports vput (see
“Command modifiers”), and manages the error number !. The first argument must be either
[+[+[+]]]e[ncode], d[ecode], s[kin] or skinl[ist] and specifies the operation to perform on the
rest of the line.
Decoding will show how a standard-compliant MUA will display the given argument, which should
be an email address. Please be aware that most MUAs have difficulties with the address
standards, and vary wildly when (comments) in parenthesis, “double-quoted” strings, or quoted-
pairs, as below, become involved. [v15 behaviour may differ] S-nail currently does not perform
decoding when displaying addresses.
Skinning is identical to decoding but only outputs the plain address, without any string,
comment etc. components. Another difference is that it may fail with the error number ! set to
^ERR-INVAL if decoding fails to find a(n) (valid) email address, in which case the unmodified
input will be output again.
skinlist first performs a skin operation, and thereafter checks a valid address for whether it
is a registered mailing list (see mlist and mlsubscribe), eventually reporting that state in
the error number ! as ^ERR-EXIST. (This state could later become overwritten by an I/O error,
though.)
Encoding supports four different modes, lesser automated versions can be chosen by prefixing
one, two or three plus signs: the standard imposes a special meaning on some characters, which
thus have to be transformed to so-called quoted-pairs by pairing them with a reverse solidus
‘\’ in order to remove the special meaning; this might change interpretation of the entire
argument from what has been desired, however! Specify one plus sign to remark that parenthesis
shall be left alone, two for not turning double quotation marks into quoted-pairs, and three
for also leaving any user-specified reverse solidus alone. The result will always be valid, if
a successful exit status is reported ([v15 behaviour may differ] the current parser fails this
assertion for some constructs). [v15 behaviour may differ] Addresses need to be specified in
between angle brackets ‘<’, ‘>’ if the construct becomes more difficult, otherwise the current
parser will fail; it is not smart enough to guess right.
? addrc enc "Hey, you",<diet@exam.ple>\ out\ there
"\"Hey, you\", \\ out\\ there" <diet@exam.ple>
? addrc d "\"Hey, you\", \\ out\\ there" <diet@exam.ple>
"Hey, you", \ out\ there <diet@exam.ple>
? addrc s "\"Hey, you\", \\ out\\ there" <diet@exam.ple>
diet@exam.ple
alias, unalias
[Only new quoting rules] (a, una) Define or list, and remove, respectively, address aliases.
Address aliases are a method of creating personal distribution lists that map a single alias
name to none to multiple receivers; aliases are expanded after message composing is completed.
The latter command removes all given aliases, the special name asterisk ‘*’ will remove all
existing aliases. When used without arguments the former shows a list of all currently known
aliases, with one argument only the target(s) of the given one. When given two arguments,
hyphen-minus ‘-’ being the first, the target(s) of the second is/are expanded recursively.
In all other cases the given address alias is newly defined or will be appended to: target
arguments must either be valid alias names, or any other address type. Recursive expansion of
(what looks like) alias name(s) targets can be prevented by prefixing the target with the
modifier reverse solidus \. A valid alias name conforms to the Postfix MTA aliases(5) rules,
and may consist of alphabetic characters, digits, the underscore, the number sign, colon,
commercial at and hyphen-minus; extensions: exclamation mark ‘!’, period ‘.’ as well as “any
character that has the high bit set” may be used: ‘[[:alnum:]_#:@!.-]+’. The number sign may
need be quoted to avoid misinterpretation as the shell comment character.
[v15 behaviour may differ] Unfortunately the colon is currently not supported, as it interferes
with normal address parsing rules. [v15 behaviour may differ] Such high bit characters will
likely cause warnings at the moment for the same reasons why colon is unsupported; also, in the
future locale dependent character set validity checks will be performed.
alternates, unalternates
[Only new quoting rules] (alt) Manage a list of alternate addresses or names of the active
user, members of which will be removed from recipient lists (except one). There is a set of
implicit alternates which is formed of the values of LOGNAME, from, sender and reply-to. from
will not be used if sender is set. The latter command removes the given list of alternates,
the special name ‘*’ will discard all existing alternate names.
The former command manages the error number !. It shows the current set of alternates when
used without arguments; in this mode only it also supports vput (see “Command modifiers”).
Otherwise the given arguments (after being checked for validity) are appended to the list of
alternate names; in posix mode they replace that list instead.
answered, unanswered
Take a message lists and mark each message as (not) having been answered. Messages will be
marked answered when being replyd to automatically if the markanswered variable is set. See
the section “Message states”.
bind, unbind
[Option][Only new quoting rules] The bind command extends the MLE (see “On terminal control and
line editor”) with freely configurable key bindings. The latter command removes from the given
context the given key binding, both of which may be specified as a wildcard ‘*’, so that, e.g.,
‘unbind * *’ will remove all bindings of all contexts. Due to initialization order unbinding
will not work for built-in key bindings upon program startup, however: please use
line-editor-no-defaults for this purpose instead.
With zero arguments, or with a context name the former command shows all key bindings (of the
given context; an asterisk ‘*’ will iterate over all contexts); a more verbose listing will be
produced if either of debug or verbose are set. With two or more arguments a binding is
(re)established: the first argument is the context to which the binding shall apply, the second
argument is a comma-separated list of the “keys” which form the binding, and any remaining
arguments form the expansion. To indicate that a binding shall not be auto-committed, but that
the expansion shall instead be furtherly editable by the user, a commercial at ‘@’ (that will
be removed) can be placed last in the expansion, from which leading and trailing whitespace
will finally be removed. Reverse solidus cannot be used as the last character of expansion.
An empty expansion will be rejected.
Contexts define when a binding applies, i.e., a binding will not be seen unless the context for
which it is defined for is currently active. This is not true for the shared binding ‘base’,
which is the foundation for all other bindings and as such always applies, its bindings,
however, only apply secondarily. The available contexts are the shared ‘base’, the ‘default’
context which is used in all not otherwise documented situations, and ‘compose’, which applies
to compose mode only.
“Keys” which form the binding are specified as a comma-separated list of byte-sequences, where
each list entry corresponds to one key(press). A list entry may, indicated by a leading colon
character ‘:’, also refer to the name of a terminal capability; several dozen names will be
compiled in and may be specified either by their terminfo(5), or, if existing, by their
termcap(5) name, regardless of the actually used [Option]al terminal control library. It is
possible to use any capability, as long as the name is resolvable by the [Option]al control
library or was defined via the internal variable termcap. Input sequences are not case-
normalized, so that an exact match is required to update or remove a binding. Examples:
? bind base $'\E',d mle-snarf-word-fwd # Esc(ape)
? bind base $'\E',$'\c?' mle-snarf-word-bwd # Esc,Delete
? bind default $'\cA',:khome,w 'echo Editable binding@'
? bind default a,b,c rm -irf / @ # Also editable
? bind default :kf1 File %
? bind compose :kf1 ~v
Note that the entire comma-separated list is first parsed (over) as a shell-token with
whitespace as the field separator, before being parsed and expanded for real with comma as the
field separator, therefore whitespace needs to be properly quoted, see “Shell-style argument
quoting”. Using Unicode reverse solidus escape sequences renders a binding defunctional if the
locale does not support Unicode (see “Character sets”), and using terminal capabilities does so
if no (corresponding) terminal control support is (currently) available.
The following terminal capability names are built-in and can be used in terminfo(5) or (if
available) the two-letter termcap(5) notation. See the respective manual for a list of
capabilities. The program infocmp(1) can be used to show all the capabilities of TERM or the
given terminal type; using the -x flag will also show supported (non-standard) extensions.
kbs or kb Backspace.
kdch1 or kD Delete character.
kDC or *4 — shifted variant.
kel or kE Clear to end of line.
kext or @9 Exit.
kich1 or kI Insert character.
kIC or #3 — shifted variant.
khome or kh Home.
kHOM or #2 — shifted variant.
kend or @7 End.
knp or kN Next page.
kpp or kP Previous page.
kcub1 or kl Left cursor (with more modifiers: see below).
kLFT or #4 — shifted variant.
kcuf1 or kr Right cursor (ditto).
kRIT or %i — shifted variant.
kcud1 or kd Down cursor (ditto).
kDN — shifted variant (only terminfo).
kcuu1 or ku Up cursor (ditto).
kUP — shifted variant (only terminfo).
kf0 or k0 Function key 0. Add one for each function key up to kf9 and k9, respectively.
kf10 or k; Function key 10.
kf11 or F1 Function key 11. Add one for each function key up to kf19 and F9,
respectively.
Some terminals support key-modifier combination extensions, e.g., ‘Alt+Shift+xy’. For example,
the delete key, kdch1: in its shifted variant, the name is mutated to kDC, then a number is
appended for the states ‘Alt’ (kDC3), ‘Shift+Alt’ (kDC4), ‘Control’ (kDC5), ‘Shift+Control’
(kDC6), ‘Alt+Control’ (kDC7), finally ‘Shift+Alt+Control’ (kDC8). The same for the left cursor
key, kcub1: KLFT, KLFT3, KLFT4, KLFT5, KLFT6, KLFT7, KLFT8.
It is advisable to use an initial escape or other control character (e.g., ‘\cA’) for bindings
which describe user key combinations (as opposed to purely terminal capability based ones), in
order to avoid ambiguities whether input belongs to key sequences or not; it also reduces
search time. Adjusting bind-timeout may help shall keys and sequences be falsely recognized.
call [Only new quoting rules] Calls the given macro, which must have been created via define (see
there for more), otherwise an ^ERR-NOENT error occurs. Calling macros recursively will at some
time excess the stack size limit, causing a hard program abortion; if recursively calling a
macro is the last command of the current macro, consider to use the command xcall, which will
first release all resources of the current macro before replacing the current macro with the
called one.
call_if Identical to call if the given macro has been created via define, but does not fail nor warn if
the macro does not exist.
cd (ch) Change the working directory to HOME or the given argument. Synonym for chdir.
certsave [Option] Only applicable to S/MIME signed messages. Takes an optional message list and a
filename and saves the certificates contained within the message signatures to the named file
in both human-readable and PEM format. The certificates can later be used to send encrypted
messages to the respective message senders by setting smime-encrypt-USER@HOST variables.
charsetalias, uncharsetalias
[Only new quoting rules] Manage alias mappings for (conversion of) “Character sets”. Alias
processing is not performed for “INTERNAL VARIABLES”, e.g., charset-8bit, and mappings are
ineffective if character set conversion is not available (features does not announce ‘+iconv’).
Expansion happens recursively for cases where aliases point to other aliases (built-in loop
limit: 8).
The latter command deletes all aliases given as arguments, or all at once when given the
asterisk ‘*’. The former shows the list of all currently defined aliases if used without
arguments, or the target of the given single argument; when given two arguments, hyphen-minus
‘-’ being the first, the second is instead expanded recursively. In all other cases the given
arguments are treated as pairs of character sets and their desired target alias name, creating
new or updating already existing aliases.
chdir (ch) Change the working directory to HOME or the given argument. Synonym for cd.
collapse, uncollapse
Only applicable to ‘thread’ed sort mode. Takes a message list and makes all replies to these
messages invisible in header summaries, except for ‘new’ messages and the “dot”. Also when a
message with collapsed replies is displayed, all of these are automatically uncollapsed. The
latter command undoes collapsing.
colour, uncolour
[Option][Only new quoting rules] Manage colour mappings of and for a “Coloured display”. The
type of colour is given as the (case-insensitive) first argument, which must be one of ‘256’
for 256-colour terminals, ‘8’, ‘ansi’ or ‘iso’ for the standard 8-colour ANSI / ISO 6429 colour
palette and ‘1’ or ‘mono’ for monochrome terminals. Monochrome terminals cannot deal with
colours, but only (some) font attributes.
Without further arguments the list of all currently defined mappings for the given colour type
is shown (as a special case giving ‘all’ or ‘*’ will show the mappings of all types).
Otherwise the second argument defines the mappable slot, and the third argument a (comma-
separated list of) colour and font attribute specification(s), and the optional fourth argument
can be used to specify a precondition: if conditioned mappings exist they are tested in
(creation) order unless a (case-insensitive) match has been found, and the default mapping (if
any has been established) will only be chosen as a last resort. The types of precondition
available depend on the mappable slot (see “Coloured display” for some examples), the following
of which exist:
Mappings prefixed with ‘mle-’ are used for the [Option]al built-in Mailx-Line-Editor (MLE, see
“On terminal control and line editor”) and do not support preconditions.
mle-position This mapping is used for the position indicator that is visible when a line
cannot be fully displayed on the screen.
mle-prompt Used for the prompt.
mle-error Used for the occasionally appearing error indicator that is joined onto prompt.
[v15 behaviour may differ] Also used for error messages written on standard
error .
Mappings prefixed with ‘sum-’ are used in header summaries, and they all understand the
preconditions ‘dot’ (the current message) and ‘older’ for elder messages (only honoured in
conjunction with datefield-markout-older).
sum-dotmark This mapping is used for the “dotmark” that can be created with the ‘%>’ or ‘%<’
formats of the variable headline.
sum-header For the complete header summary line except the “dotmark” and the thread
structure.
sum-thread For the thread structure which can be created with the ‘%i’ format of the
variable headline.
Mappings prefixed with ‘view-’ are used when displaying messages.
view-from_ This mapping is used for so-called ‘From_’ lines, which are MBOX file format
specific header lines (also see mbox-rfc4155).
view-header For header lines. A comma-separated list of headers to which the mapping
applies may be given as a precondition; if the [Option]al regular expression
support is available then if any of the “magic regular expression characters” is
seen the precondition will be evaluated as (an extended) one.
view-msginfo For the introductional message info line.
view-partinfo For MIME part info lines.
The following (case-insensitive) colour definitions and font attributes are understood,
multiple of which can be specified in a comma-separated list:
ft= a font attribute: ‘bold’, ‘reverse’ or ‘underline’. It is possible (and often applicable)
to specify multiple font attributes for a single mapping.
fg= foreground colour attribute: ‘black’, ‘blue’, ‘green’, ‘red’, ‘brown’, ‘magenta’, ‘cyan’
or ‘white’. To specify a 256-colour mode a decimal number colour specification in the
range 0 to 255, inclusive, is supported, and interpreted as follows:
0 - 7 the standard ISO 6429 colours, as above.
8 - 15 high intensity variants of the standard colours.
16 - 231 216 colours in tuples of 6.
232 - 255 grayscale from black to white in 24 steps.
#!/bin/sh -
fg() { printf "\033[38;5;${1}m($1)"; }
bg() { printf "\033[48;5;${1}m($1)"; }
i=0
while [ $i -lt 256 ]; do fg $i; i=$(($i + 1)); done
printf "\033[0m\n"
i=0
while [ $i -lt 256 ]; do bg $i; i=$(($i + 1)); done
printf "\033[0m\n"
bg= background colour attribute (see fg= for possible values).
The command uncolour will remove for the given colour type (the special type ‘*’ selects all)
the given mapping; if the optional precondition argument is given only the exact tuple of
mapping and precondition is removed. The special name ‘*’ will remove all mappings (no
precondition allowed), thus ‘uncolour * *’ will remove all established mappings.
commandalias, uncommandalias
[Only new quoting rules] Define or list, and remove, respectively, command aliases. An
(command)alias can be used everywhere a normal command can be used, but always takes
precedence: any arguments that are given to the command alias are joined onto the alias
expansion, and the resulting string forms the command line that is, in effect, executed. The
latter command removes all given aliases, the special name asterisk ‘*’ will remove all
existing aliases. When used without arguments the former shows a list of all currently known
aliases, with one argument only the expansion of the given one.
With two or more arguments a command alias is defined or updated: the first argument is the
name under which the remaining command line should be accessible, the content of which can be
just about anything. An alias may itself expand to another alias, but to avoid expansion loops
further expansion will be prevented if an alias refers to itself or if an expansion depth limit
is reached. Explicit expansion prevention is available via reverse solidus \, one of the
“Command modifiers”.
? commandalias xx
s-nail: `commandalias': no such alias: xx
? commandalias xx echo hello,
? commandalias xx
commandalias xx 'echo hello,'
? xx
hello,
? xx world
hello, world
Copy (C) Copy messages to files whose names are derived from the author of the respective message
and do not mark them as being saved; otherwise identical to Save.
copy (c) Copy messages to the named file and do not mark them as being saved; otherwise identical to
save.
csop [Only new quoting rules] A multiplexer command which provides C-style string operations on
8-bit bytes without a notion of locale settings and character sets, effectively assuming ASCII
data. For numeric and other operations refer to vexpr. vput, one of the “Command modifiers”,
is supported. The error result is ‘-1’ for usage errors and numeric results, the empty string
otherwise; missing data errors, as for unsuccessful searches, result in the ! error number
being set to ^ERR-NODATA. Where the question mark ‘?’ modifier suffix is supported, a case-
insensitive (ASCII mapping) operation mode is supported; the keyword ‘case’ is optional, e.g.,
‘find?’ and ‘find?case’ are identical.
length Queries the length of the given argument.
hash, hash32 Calculates a hash value of the given argument. The latter will return a 32-bit
result regardless of host environment. ‘?’ modifier suffix is supported. These use
Chris Torek's hash algorithm, the resulting hash value is bit mixed as shown by Bret
Mulvey.
find Search for the second in the first argument. Shows the resulting 0-based offset
shall it have been found. ‘?’ modifier suffix is supported.
substring Creates a substring of its first argument. The optional second argument is the
0-based starting offset, a negative one counts from the end; the optional third
argument specifies the length of the desired result, a negative length leaves off the
given number of bytes at the end of the original string; by default the entire string
is used. This operation tries to work around faulty arguments (set verbose for error
logs), but reports them via the error number ! as ^ERR-OVERFLOW.
trim Trim away whitespace characters from both ends of the argument.
trim-front Trim away whitespace characters from the begin of the argument.
trim-end Trim away whitespace characters from the end of the argument.
cwd Show the name of the current working directory, as reported by getcwd(3). Supports vput (see
“Command modifiers”). The return status is tracked via ?.
Decrypt [Option] For unencrypted messages this command is identical to Copy; Encrypted messages are
first decrypted, if possible, and then copied.
decrypt [Option] For unencrypted messages this command is identical to copy; Encrypted messages are
first decrypted, if possible, and then copied.
define, undefine
The latter command deletes the given macro, the special name ‘*’ will discard all existing
macros. Deletion of (a) macro(s) can be performed from within running (a) macro(s), including
self-deletion. Without arguments the former command prints the current list of macros,
including their content, otherwise it defines a macro, replacing an existing one of the same
name as applicable.
A defined macro can be invoked explicitly by using the call, call_if and xcall commands, or
implicitly if a macro hook is triggered, e.g., a folder-hook. Execution of a macro body can be
stopped from within by calling return.
Temporary macro block-scope variables can be created or deleted with the local command modifier
in conjunction with the commands set and unset, respectively. To enforce unrolling of changes
made to (global) “INTERNAL VARIABLES” the command localopts can be used instead; its covered
scope depends on how (i.e., “as what”: normal macro, folder hook, hook, account switch) the
macro is invoked.
Inside a called macro, the given positional parameters are implicitly local to the macro's
scope, and may be accessed via the variables *, @, # and 1 and any other positive unsigned
decimal number less than or equal to #. Positional parameters can be shifted, or become
completely replaced, removed etc. via vpospar. A helpful command for numeric computation and
string evaluations is vexpr, csop offers C-style byte string operations.
define name {
command1
command2
...
commandN
}
# E.g.
define exmac {
echo Parameter 1 of ${#} is ${1}, all: ${*} / ${@}
return 1000 0
}
call exmac Hello macro exmac!
echo ${?}/${!}/${^ERRNAME}
delete, undelete
(d, u) Marks the given message list as being or not being ‘deleted’, respectively; if no
argument has been specified then the usual search for a visible message is performed, as
documented for “Message list arguments”, showing only the next input prompt if the search
fails. Deleted messages will neither be saved in the “secondary mailbox” MBOX nor will they be
available for most other commands. If the autoprint variable is set, the new “dot” or the last
message restored, respectively, is automatically typed; also see dp, dt.
digmsg [Only new quoting rules] Digging (information out of) messages is possible through digmsg
objects, which can be created for the given message number; in compose mode the hyphen-minus
‘-’ will instead open the message that is being composed. If a hyphen-minus is given as the
optional third argument then output will be generated on the standard output channel instead of
being subject to consumation by the read or readall commands.
The objects may be removed again by giving the same identifier used for creation; this step
could be omitted: objects will be automatically closed when the active mailbox or the compose
mode is left, respectively. In all other use cases the second argument is an object
identifier, and the third and all following arguments are interpreted as via ~^ (see “COMMAND
ESCAPES”):
? vput = msgno; digmsg create $msgno
? digmsg $msgno header list; readall x; echon $x
210 Subject From To Message-ID References In-Reply-To Status
? digmsg $msgno header show Status;readall x;echon $x
212 Status
RO
? digmsg remove $msgno
discard (di) Identical to ignore. Superseded by the multiplexer headerpick.
dp, dt Delete the given messages and automatically type the new “dot” if one exists, regardless of the
setting of autoprint.
dotmove Move the “dot” up or down by one message when given ‘+’ or ‘-’ argument, respectively.
draft, undraft
Take message lists and mark each given message as being draft, or not being draft,
respectively, as documented in the section “Message states”.
echo [Only new quoting rules] (ec) Echoes arguments to standard output and writes a trailing
newline, whereas the otherwise identical echon does not. “Shell-style argument quoting” is
used, “Filename transformations” are applied to the expanded arguments. This command also
supports vput as documented in “Command modifiers”, and manages the error number !: if data is
stored in a variable then the return value reflects the length of the result string in case of
success and is ‘-1’ on error.
echoerr [Only new quoting rules] Identical to echo except that is echoes to standard error. Also see
echoerrn. In interactive sessions the [Option]al message ring queue for errors will be used
instead, if available and vput was not used.
echon [Only new quoting rules] Identical to echo, but does not write or store a trailing newline.
echoerrn [Only new quoting rules] Identical to echoerr, but does not write or store a trailing newline.
edit (e) Point the text EDITOR at each message from the given list in turn. Modified contents are
discarded unless the writebackedited variable is set, and are not used unless the mailbox can
be written to and the editor returns a successful exit status. visual can be used instead for
a more display oriented editor.
elif Part of the if (see there for more), elif, else, endif conditional — if the condition of a
preceding if was false, check the following condition and execute the following block if it
evaluates true.
else (el) Part of the if (see there for more), elif, else, endif conditional — if none of the
conditions of the preceding if and elif commands was true, the else block is executed.
endif (en) Marks the end of an if (see there for more), elif, else, endif conditional execution
block.
environ [Only new quoting rules] S-nail has a strict notion about which variables are “INTERNAL
VARIABLES” and which are managed in the program “ENVIRONMENT”. Since some of the latter are a
vivid part of S-nails functioning, however, they are transparently integrated into the normal
handling of internal variables via set and unset. To integrate other environment variables of
choice into this transparent handling, and also to export internal variables into the process
environment where they normally are not, a ‘link’ needs to become established with this
command, as in, e.g.,
environ link PERL5LIB TZ
Afterwards changing such variables with set will cause automatic updates of the program
environment, and therefore be inherited by newly created child processes. Sufficient system
support provided (it was in BSD as early as 1987, and is standardized since Y2K) removing such
variables with unset will remove them also from the program environment, but in any way the
knowledge they ever have been ‘link’ed will be lost. Note that this implies that localopts may
cause loss of such links.
The command ‘unlink’ will remove an existing link, but leaves the variables as such intact.
Additionally the subcommands ‘set’ and ‘unset’ are provided, which work exactly the same as the
documented commands set and unset, but (additionally un)link the variable(s) with the program
environment and thus immediately export them to, or remove them from (if possible),
respectively, the program environment.
errors [Option] Since S-nail uses the console as a user interface it can happen that messages scroll
by too fast to become recognized. Therefore an error log queue is available which can be
managed by errors: show or no argument will display and clear the queue, clear will only clear
the queue. The queue is finite: if its maximum size is reached any new message replaces the
eldest. There are also the variables ^ERRQUEUE-COUNT and ^ERRQUEUE-EXISTS.
eval [Only new quoting rules] Construct a command by concatenating the arguments, separated with a
single space character, and then evaluate the result. This command passes through the exit
status ? and error number ! of the evaluated command; also see call.
define xxx {
echo "xxx arg <$1>"
shift
if [ $# -gt 0 ]
\xcall xxx "$@"
endif
}
define yyy {
eval "$@ ' ball"
}
call yyy '\call xxx' "b\$'\t'u ' "
call xxx arg <b u>
call xxx arg < >
call xxx arg <ball>
exit (ex or x) Exit from S-nail without changing the active mailbox and skip any saving of messages
in the “secondary mailbox” MBOX, as well as a possibly tracked line editor history-file. A
possibly set on-account-cleanup will be invoked, however. The optional status number argument
will be passed through to exit(3). [v15 behaviour may differ] For now it can happen that the
given status will be overwritten, later this will only occur if a later error needs to be
reported onto an otherwise success indicating status.
File (Fi) Like file, but open the mailbox read-only.
file (fi) The file command switches to a new mailbox. Without arguments it shows status information
of the current mailbox. If an argument is given, it will write out changes (such as deletions)
the user has made, open a new mailbox, update the internal variables mailbox-resolved and
mailbox-display, execute an according folder-hook, if one is installed, and optionally display
a summary of headers if the variable header is set.
“Filename transformations” will be applied to the name argument, and ‘protocol://’ prefixes
are, i.e., URL syntax is understood, e.g., ‘mbox:///tmp/mdirbox’: if a protocol prefix is used
the mailbox type is fixated and neither the auto-detection (read on) nor the newfolders
mechanisms apply. [Option]ally URLs can also be used to access network resources, which may be
accessed securely via “Encrypted network communication” if so supported. Network communication
socket timeouts are configurable, e.g., socket-connect-timeout. All generated network traffic
may be proxied over the SOCKS5 server given in socks-proxy.
[v15-compat] protocol://[user[:password]@]host[:port][/path]
[no v15-compat] protocol://[user@]host[:port][/path]
[Option]ally supported network protocols are pop3 (POP3) and pop3s (POP3 with TLS encrypted
transport), imap and imaps. The [/path] part is valid only for IMAP; there it defaults to
INBOX. Network URLs require a special encoding as documented in the section “On URL syntax and
credential lookup”.
If the resulting file protocol (MBOX database) name is located on a local filesystem then the
list of all registered filetypes is traversed in order to see whether a transparent
intermediate conversion step is necessary to handle the given mailbox, in which case S-nail
will use the found hook to load and save data into and from a temporary file, respectively.
Changing hooks will not affect already opened mailboxes. For example, the following creates
hooks for the gzip(1) compression tool and a combined compressed and encrypted format:
? filetype \
gzip 'gzip -dc' 'gzip -c' \
zst.pgp 'gpg -d | zstd -dc' 'zstd -19 -zc | gpg -e'
filetypes also provide limited (case-sensitive) auto-completion capabilities. For example
‘mbox.gz’ will be found for ‘? file mbox’ provided that a corresponding handler is installed.
It will neither find ‘mbox.GZ’ nor ‘mbox.Gz’ however, on the other hand doing an explicit ‘?
file mbox.GZ’ will find and use the handler for ‘gz’.
MBOX databases will always be protected via file-region locks (fcntl(2)) during file operations
in order to avoid inconsistencies due to concurrent modifications. [Option] In addition
mailbox files treated as the system inbox (MAIL), as well as “primary system mailbox”es in
general will also be protected by so-called dotlock files, the traditional way of mail spool
file locking: for any file ‘x’ a lock file ‘x.lock’ will be created for the duration of the
synchronization — as necessary an external privileged dotlock helper will be used to create the
dotlock file in the same directory and with the same user and group identities as the file of
interest. dotlock-disable can be used to turn off additional dotlock files, shall the need
arise. There is also a related entry in the “FAQ”: “Howto handle stale dotlock files”.
S-nail by default uses tolerant POSIX rules when reading MBOX database files, but it will
detect invalid message boundaries in this mode and complain (even more with debug) if any is
seen: in this case mbox-rfc4155 can be used to create a valid MBOX database from the invalid
input.
[Option] If no protocol has been fixated, and name refers to a directory with the
subdirectories ‘tmp’, ‘new’ and ‘cur’, then it is treated as a folder in “Maildir” format. The
maildir format stores each message in its own file, and has been designed so that file locking
is not necessary when reading or writing files.
[v15 behaviour may differ] If no protocol has been fixated and no existing file has been found,
the variable newfolders controls the format of mailboxes yet to be created.
filetype, unfiletype
[Only new quoting rules] Define, list, and remove, respectively, file handler hooks, which
provide (shell) commands that enable S-nail to load and save MBOX files from and to files with
the registered file extensions, as shown and described for file. The extensions are used case-
insensitively, yet the auto-completion feature of, e.g., file will only work case-sensitively.
An intermediate temporary file will be used to store the expanded data. The latter command
will remove hooks for all given extensions, asterisk ‘*’ will remove all existing handlers.
When used without arguments the former shows a list of all currently defined file hooks, with
one argument the expansion of the given alias. Otherwise three arguments are expected, the
first specifying the file extension for which the hook is meant, and the second and third
defining the load- and save commands to deal with the file type, respectively, both of which
must read from standard input and write to standard output. Changing hooks will not affect
already opened mailboxes ([v15 behaviour may differ] except below). [v15 behaviour may differ]
For now too much work is done, and files are oftened read in twice where once would be
sufficient: this can cause problems if a filetype is changed while such a file is opened; this
was already so with the built-in support of .gz etc. in Heirloom, and will vanish in v15. [v15
behaviour may differ] For now all handler strings are passed to the SHELL for evaluation
purposes; in the future a ‘!’ prefix to load and save commands may mean to bypass this shell
instance: placing a leading space will avoid any possible misinterpretations.
? filetype bz2 'bzip2 -dc' 'bzip2 -zc' \
gz 'gzip -dc' 'gzip -c' xz 'xz -dc' 'xz -zc' \
zst 'zstd -dc' 'zstd -19 -zc' \
zst.pgp 'gpg -d | zstd -dc' 'zstd -19 -zc | gpg -e'
? set record=+sent.zst.pgp
flag, unflag
Take message lists and mark the messages as being flagged, or not being flagged, respectively,
for urgent/special attention. See the section “Message states”.
folder (fold) The same as file.
folders With no arguments, list the names of the folders in the folder directory. With an existing
folder as an argument, lists the names of folders below the named folder.
Followup (F) Similar to Respond, but saves the message in a file named after the local part of the first
recipient's address (instead of in record).
followup (fo) Similar to respond, but saves the message in a file named after the local part of the
first recipient's address (instead of in record).
followupall
Similar to followup, but responds to all recipients regardless of the flipr variable.
followupsender
Similar to Followup, but responds to the sender only regardless of the flipr variable.
Forward Similar to forward, but saves the message in a file named after the local part of the
recipient's address (instead of in record).
forward Takes a message and the address of a recipient and forwards the message to him. The text of
the original message is included in the new one, with the value of the forward-inject-head
variable preceding, and the value of forward-inject-tail succeeding it. To filter the included
header fields to the desired subset use the ‘forward’ slot of the white- and blacklisting
command headerpick. Only the first part of a multipart message is included unless
forward-as-attachment, and recipient addresses will be stripped from comments, names etc.
unless the internal variable fullnames is set.
This may generate the errors ^ERR-DESTADDRREQ if no receiver has been specified, ^ERR-PERM if
some addressees where rejected by expandaddr, ^ERR-NODATA if no applicable messages have been
given, ^ERR-NOTSUP if multiple messages have been specified, ^ERR-IO if an I/O error occurs,
^ERR-NOTSUP if a necessary character set conversion fails, and ^ERR-INVAL for other errors.
from (f) Takes a list of message specifications and displays a summary of their message headers,
exactly as via headers, making the first message of the result the new “dot” (the last message
if showlast is set). An alias of this command is search. Also see “Specifying messages”.
Fwd [Obsolete] Alias for Forward.
fwd [Obsolete] Alias for forward.
fwdignore
[Obsolete] Superseded by the multiplexer headerpick.
fwdretain
[Obsolete] Superseded by the multiplexer headerpick.
ghost, unghost
[Obsolete] Replaced by commandalias, uncommandalias.
headerpick, unheaderpick
[Only new quoting rules] Multiplexer command to manage white- and blacklisting selections of
header fields for a variety of applications. Without arguments the set of contexts that have
settings is displayed. When given arguments, the first argument is the context to which the
command applies, one of (case-insensitive) ‘type’ for display purposes (via, e.g., type),
‘save’ for selecting which headers shall be stored persistently when save, copy, move or even
decrypting messages (note that MIME related etc. header fields should not be ignored in order
to not destroy usability of the message in this case), ‘forward’ for stripping down messages
when forwarding message (has no effect if forward-as-attachment is set), and ‘top’ for defining
user-defined set of fields for the command top.
The current settings of the given context are displayed if it is the only argument. A second
argument denotes the type of restriction that is to be chosen, it may be (a case-insensitive
prefix of) ‘retain’ or ‘ignore’ for white- and blacklisting purposes, respectively.
Establishing a whitelist suppresses inspection of the corresponding blacklist.
If no further argument is given the current settings of the given type will be displayed,
otherwise the remaining arguments specify header fields, which [Option]ally may be given as
regular expressions, to be added to the given type. The special wildcard field (asterisk, ‘*’)
will establish a (fast) shorthand setting which covers all fields.
The latter command always takes three or more arguments and can be used to remove selections,
i.e., from the given context, the given type of list, all the given headers will be removed,
the special argument ‘*’ will remove all headers.
headers (h) Show the current group of headers, the size of which depends on the variable screen in
interactive mode, and the format of which can be defined with headline. If a message-
specification is given the group of headers containing the first message therein is shown and
the message at the top of the screen becomes the new “dot”; the last message is targeted if
showlast is set.
help (hel) A synonym for ?.
history [Option] Without arguments or when given show all history entries are shown (this mode also
supports a more verbose output). load will replace the list of entries with the content of
history-file, and save will dump the current list to said file, replacing former content.
clear will delete all history entries. The argument can also be a signed decimal NUMBER, which
will select and evaluate the respective history entry, and move it to the top of the history; a
negative number is used as an offset to the current command, e.g., ‘-1’ will select the last
command, the history top. Please see “On terminal control and line editor” for more on this
topic.
hold (ho, also preserve) Takes a message list and marks each message therein to be saved in the
user's system inbox instead of in the “secondary mailbox” MBOX. Does not override the delete
command. S-nail deviates from the POSIX standard with this command, because a next command
issued after hold will display the following message, not the current one.
if (i) Part of the if, elif, else, endif conditional execution construct — if the given condition
is true then the encapsulated block is executed. The POSIX standard only supports the (case-
insensitive) conditions ‘r’eceive and ‘s’end, the remaining are non-portable extensions. [v15
behaviour may differ] In conjunction with the wysh command prefix(es) “Shell-style argument
quoting” and more test operators are available.
if receive
commands ...
else
commands ...
endif
Further (case-insensitive) one-argument conditions are ‘t’erminal which evaluates to true in
interactive terminal sessions (running with standard input or standard output attached to a
terminal, and none of the “quickrun” command line options -e, -H and -L have been used), as
well as any boolean value (see “INTERNAL VARIABLES” for textual boolean representations) to
mark an enwrapped block as “never execute” or “always execute”. (Remarks: condition syntax
errors skip all branches until endif.)
[no v15-compat] and without wysh: It is possible to check “INTERNAL VARIABLES” as well as
“ENVIRONMENT” variables for existence or compare their expansion against a user given value or
another variable by using the ‘$’ (“variable next”) conditional trigger character; a variable
on the right hand side may be signalled using the same mechanism. Variable names may be
enclosed in a pair of matching braces. When this mode has been triggered, several operators
are available ([v15-compat] and wysh: they are always available, and there is no trigger:
variables will have been expanded by the shell-compatible parser before the if etc. command
sees them).
[v15-compat] Two argument conditions. Variables can be tested for existence and expansion:
‘-N’ will test whether the given variable exists, e.g., ‘-N editalong’ will evaluate to true
when editalong is set, whereas ‘-Z editalong’ will if it is not. ‘-n "$editalong"’ will be
true if the variable is set and expands to a non-empty string, ‘-z $'\$editalong'’ only if the
expansion is empty, whether the variable exists or not. The remaining conditions take three
arguments.
Integer operators treat the arguments on the left and right hand side of the operator as
integral numbers and compare them arithmetically. It is an error if any of the operands is not
a valid integer, an empty argument (which implies it had been quoted) is treated as if it were
0. Via the question mark ‘?’ modifier suffix a saturated operation mode is available where
numbers will linger at the minimum or maximum possible value, instead of overflowing (or
trapping), the keyword ‘saturated’ is optional, e.g., ‘==?’, ‘==?satu’ and ‘==?saturated’ are
identical. Available operators are ‘-lt’ (less than), ‘-le’ (less than or equal to), ‘-eq’
(equal), ‘-ne’ (not equal), ‘-ge’ (greater than or equal to), and ‘-gt’ (greater than).
String and regular expression data operators compare the left and right hand side according to
their textual content. Unset variables are treated as the empty string. Via the question mark
‘?’ modifier suffix a case-insensitive operation mode is available, the keyword ‘case’ is
optional, e.g., ‘==?’ and ‘==?case’ are identical.
Available string operators are ‘<’ (less than), ‘<=’ (less than or equal to), ‘==’ (equal),
‘!=’ (not equal), ‘>=’ (greater than or equal to), ‘>’ (greater than), ‘=%’ (is substring of)
and ‘!%’ (is not substring of). By default these operators work on bytes and (therefore) do
not take into account character set specifics. If the case-insensitivity modifier has been
used, case is ignored according to the rules of the US-ASCII encoding, i.e., bytes are still
compared.
When the [Option]al regular expression support is available, the additional string operators
‘=~’ and ‘!~’ can be used. They treat the right hand side as an extended regular expression
that is matched according to the active locale (see “Character sets”), i.e., character sets
should be honoured correctly.
Conditions can be joined via AND-OR lists (where the AND operator is ‘&&’ and the OR operator
is ‘||’), which have equal precedence and will be evaluated with left associativity, thus using
the same syntax that is known for the sh(1). It is also possible to form groups of conditions
and lists by enclosing them in pairs of brackets ‘[ ... ]’, which may be interlocked within
each other, and also be joined via AND-OR lists.
The results of individual conditions and entire groups may be modified via unary operators: the
unary operator ‘!’ will reverse the result.
wysh set v15-compat=yes # with value: automatic "wysh"!
if -N debug;echo *debug* set;else;echo not;endif
if [ "$ttycharset" == UTF-8 ] || \
[ "$ttycharset" ==?case UTF8 ]
echo *ttycharset* is UTF-8, the former case-sensitive!
endif
set t1=one t2=one
if [ "${t1}" == "${t2}" ]
echo These two variables are equal
endif
if "$features" =% +regex && "$TERM" =~?case "^xterm.*"
echo ..in an X terminal
endif
if [ [ true ] && [ [ "${debug}" != '' ] || \
[ "$verbose" != '' ] ] ]
echo Noisy, noisy
endif
if true && [ -n "$debug" || -n "${verbose}" ]
echo Left associativity, as is known from the shell
endif
ignore (ig) Identical to discard. Superseded by the multiplexer headerpick.
list Shows the names of all available commands, alphabetically sorted. If given any non-whitespace
argument the list will be shown in the order in which command prefixes are searched. [Option]
In conjunction with a set variable verbose additional information will be provided for each
command: the argument type will be indicated, the documentation string will be shown, and the
set of command flags will show up:
‘`local'’ command supports the command modifier local.
‘`vput'’ command supports the command modifier vput.
‘*!*’ the error number is tracked in !.
‘needs-box’ whether the command needs an active mailbox, a file.
‘ok:’ indicators whether command is ...
‘batch/interactive’
usable in interactive or batch mode (-#).
‘send-mode’ usable in send mode.
‘subprocess’ allowed to be used when running in a subprocess instance, e.g., from
within a macro that is called via on-compose-splice.
‘not ok:’ indicators whether command is not ...
‘compose-mode’ available in compose mode.
‘startup’ available during program startup, e.g., in “Resource files”.
‘gabby’ The command produces history-gabby history entries.
localopts
Enforce change localization of environ (linked) “ENVIRONMENT” as well as (global) “INTERNAL
VARIABLES”, meaning that their state will be reverted to the former one once the “covered
scope” is left. Just like the command modifier local, which provides block-scope localization
for some commands (instead), it can only be used inside of macro definition blocks introduced
by account or define. The covered scope of an account is left once a different account is
activated, and some macros, notably folder-hooks, use their own specific notion of covered
scope, here it will be extended until the folder is left again.
This setting stacks up: i.e., if ‘macro1’ enables change localization and calls ‘macro2’, which
explicitly resets localization, then any value changes within ‘macro2’ will still be reverted
when the scope of ‘macro1’ is left. (Caveats: if in this example ‘macro2’ changes to a
different account which sets some variables that are already covered by localizations, their
scope will be extended, and in fact leaving the account will (thus) restore settings in
(likely) global scope which actually were defined in a local, macro private context!)
This command takes one or two arguments, the optional first one specifies an attribute that may
be one of scope, which refers to the current scope and is thus the default, call, which causes
any macro that is being called to be started with localization enabled by default, as well as
call-fixate, which (if enabled) disallows any called macro to turn off localization: like this
it can be ensured that once the current scope regains control, any changes made in deeper
levels have been reverted. The latter two are mutually exclusive, and neither affects xcall.
The (second) argument is interpreted as a boolean (string, see “INTERNAL VARIABLES”) and states
whether the given attribute shall be turned on or off.
define temporary_settings {
set possibly_global_option1
localopts on
set localized_option1
set localized_option2
localopts scope off
set possibly_global_option2
}
Lreply Reply to messages that come in via known (mlist) or subscribed (mlsubscribe) mailing lists, or
pretend to do so (see “Mailing lists”): on top of the usual reply functionality this will
actively resort and even remove message recipients in order to generate a message that is
supposed to be sent to a mailing list. For example it will also implicitly generate a
‘Mail-Followup-To:’ header if that seems useful, regardless of the setting of the variable
followup-to. For more documentation please refer to “On sending mail, and non-interactive
mode”.
This may generate the errors ^ERR-DESTADDRREQ if no receiver has been specified, ^ERR-PERM if
some addressees where rejected by expandaddr, ^ERR-NODATA if no applicable messages have been
given, ^ERR-IO if an I/O error occurs, ^ERR-NOTSUP if a necessary character set conversion
fails, and ^ERR-INVAL for other errors. Occurrence of some of the errors depend on the value
of expandaddr. Any error stops processing of further messages.
Mail Similar to mail, but saves the message in a file named after the local part of the first
recipient's address (instead of in record).
mail (m) Takes a (list of) recipient address(es) as (an) argument(s), or asks on standard input if
none were given; then collects the remaining mail content and sends it out. Unless the
internal variable fullnames is set recipient addresses will be stripped from comments, names
etc. For more documentation please refer to “On sending mail, and non-interactive mode”.
This may generate the errors ^ERR-DESTADDRREQ if no receiver has been specified, ^ERR-PERM if
some addressees where rejected by expandaddr, ^ERR-NODATA if no applicable messages have been
given, ^ERR-NOTSUP if multiple messages have been specified, ^ERR-IO if an I/O error occurs,
^ERR-NOTSUP if a necessary character set conversion fails, and ^ERR-INVAL for other errors.
Occurrence of some of the errors depend on the value of expandaddr.
mbox (mb) The given message list is to be sent to the “secondary mailbox” MBOX when S-nail is quit;
this is the default action unless the variable hold is set. [v15 behaviour may differ] This
command can only be used in a “primary system mailbox”.
mimetype, unmimetype
[Only new quoting rules] Without arguments the content of the MIME type cache will displayed; a
more verbose listing will be produced if either of debug or verbose are set. When given
arguments they will be joined, interpreted as shown in “The mime.types files” (also see “HTML
mail and MIME attachments”), and the resulting entry will be added (prepended) to the cache.
In any event MIME type sources are loaded first as necessary – mimetypes-load-control can be
used to fine-tune which sources are actually loaded.
The latter command deletes all specifications of the given MIME type, thus ‘? unmimetype
text/plain’ will remove all registered specifications for the MIME type ‘text/plain’. The
special name ‘*’ will discard all existing MIME types, just as will ‘reset’, but which also
reenables cache initialization via mimetypes-load-control.
mimeview [v15 behaviour may differ] Only available in interactive mode, this command allows one to
display MIME parts which require external MIME handler programs to run which do not integrate
in S-nails normal type output (see “HTML mail and MIME attachments”). ([v15 behaviour may
differ] No syntax to directly address parts, this restriction may vanish.) The user will be
asked for each non-text part of the given message in turn whether the registered handler shall
be used to display the part.
mlist, unmlist
[Only new quoting rules] Manage the list of known “Mailing lists”; subscriptions are controlled
via mlsubscribe. The latter command deletes all given arguments, or all at once when given the
asterisk ‘*’. The former shows the list of all currently known lists if used without
arguments, otherwise the given arguments will become known. [Option] In the latter case,
arguments which contain any of the “magic regular expression characters” will be interpreted as
one, possibly matching many addresses; these will be sequentially matched via linked lists
instead of being looked up in a dictionary.
mlsubscribe, unmlsubscribe
Building upon the command pair mlist, unmlist, but only managing the subscription attribute of
mailing lists. (The former will also create not yet existing mailing lists.)
Move Similar to move, but moves the messages to a file named after the local part of the sender
address of the first message (instead of in record).
move Acts like copy but marks the messages for deletion if they were transferred successfully.
More Like more, but also displays header fields which would not pass the headerpick selection, and
all MIME parts. Identical to Page.
more Invokes the PAGER on the given messages, even in non-interactive mode and as long as the
standard output is a terminal. Identical to page.
netrc [Option] When used without arguments or if show has been given the content of the ~/.netrc
cache is shown, loading it first as necessary. If the argument is load then the cache will
only be initialized and clear will remove its contents. Note that S-nail will try to load the
file only once, use ‘netrc clear’ to unlock further attempts. See netrc-lookup, netrc-pipe and
the section “On URL syntax and credential lookup”; the section “The .netrc file” documents the
file format in detail.
newmail Checks for new mail in the current folder without committing any changes before. If new mail
is present, a message is shown. If the header variable is set, the headers of each new message
are also shown. This command is not available for all mailbox types.
next (n) (like ‘+’ or “ENTER”) Goes to the next message in sequence and types it. With an argument
list, types the next matching message.
New Same as Unread.
new Same as unread.
noop If the current folder is accessed via a network connection, a “NOOP” command is sent, otherwise
no operation is performed.
Page Like page, but also displays header fields which would not pass the headerpick selection, and
all MIME parts. Identical to More.
page Invokes the PAGER on the given messages, even in non-interactive mode and as long as the
standard output is a terminal. Identical to more.
Pipe Like pipe but also pipes header fields which would not pass the headerpick selection, and all
parts of MIME ‘multipart/alternative’ messages.
pipe (pi) Takes an optional message list and shell command (that defaults to cmd), and pipes the
messages through the command. If the page variable is set, every message is followed by a
formfeed character.
preserve (pre) A synonym for hold.
Print (P) Alias for Type.
print (p) Research Unix equivalent of type.
quit (q) Terminates the session, saving all undeleted, unsaved messages in the current “secondary
mailbox” MBOX, preserving all messages marked with hold or preserve or never referenced in the
system inbox, and removing all other messages from the “primary system mailbox”. If new mail
has arrived during the session, the message “You have new mail” will be shown. If given while
editing a mailbox file with the command line option -f, then the edit file is rewritten. A
return to the shell is effected, unless the rewrite of edit file fails, in which case the user
can escape with the exit command. The optional status number argument will be passed through
to exit(3). [v15 behaviour may differ] For now it can happen that the given status will be
overwritten, later this will only occur if a later error needs to be reported onto an otherwise
success indicating status.
read [Only new quoting rules] Read a line from standard input, or the channel set active via
readctl, and assign the data, which will be split as indicated by ifs, to the given variables.
The variable names are checked by the same rules as documented for vput, and the same error
codes will be seen in !; the exit status ? indicates the number of bytes read, it will be ‘-1’
with the error number ! set to ^ERR-BADF in case of I/O errors, or ^ERR-NONE upon End-Of-File.
If there are more fields than variables, assigns successive fields to the last given variable.
If there are less fields than variables, assigns the empty string to the remains.
? read a b c
H e l l o
? echo "<$a> <$b> <$c>"
<H> <e> <l l o>
? wysh set ifs=:; read a b c;unset ifs
hey2.0,:"'you ",:world!:mars.:
? echo $?/$^ERRNAME / <$a><$b><$c>
0/NONE / <hey2.0,><"'you ",><world!:mars.:><><>
readall [Only new quoting rules] Read anything from standard input, or the channel set active via
readctl, and assign the data to the given variable. The variable name is checked by the same
rules as documented for vput, and the same error codes will be seen in !; the exit status ?
indicates the number of bytes read, it will be ‘-1’ with the error number ! set to ^ERR-BADF in
case of I/O errors, or ^ERR-NONE upon End-Of-File. [v15 behaviour may differ] The input data
length is restricted to 31-bits.
readctl [Only new quoting rules] Manages input channels for read and readall, to be used to avoid
complicated or impracticable code, like calling read from within a macro in non-interactive
mode. Without arguments, or when the first argument is show, a listing of all known channels
is printed. Channels can otherwise be created, and existing channels can be set active and
removed by giving the string used for creation.
The channel name is expected to be a file descriptor number, or, if parsing the numeric fails,
an input file name that undergoes “Filename transformations”. E.g. (this example requires a
modern shell):
$ LC_ALL=C printf 'echon "hey, "\nread a\nyou\necho $a' |\
LC_ALL=C s-nail -R#
hey, you
$ LC_ALL=C printf 'echon "hey, "\nread a\necho $a' |\
LC_ALL=C 6<<< 'you' s-nail -R#X'readctl create 6'
hey, you
remove Removes the named files or directories. “Filename transformations” including shell pathname
wildcard pattern expansions (glob(7)) are performed on the arguments. If a name refer to a
mailbox, e.g., a Maildir mailbox, then a mailbox type specific removal will be performed,
deleting the complete mailbox. The user is asked for confirmation in interactive mode.
rename Takes the name of an existing folder and the name for the new folder and renames the first to
the second one. “Filename transformations” including shell pathname wildcard pattern
expansions (glob(7)) are performed on both arguments. Both folders must be of the same type.
Reply (R) Identical to reply except that it replies to only the sender of each message of the given
list, by using the first message as the template to quote, for the ‘Subject:’ etc.; setting
flipr will exchange this command with reply.
reply (r) Take a message and group-responds to it by addressing the sender and all recipients,
subject to alternates processing. followup-to, followup-to-honour, reply-to-honour as well as
recipients-in-cc influence response behaviour. Unless the internal variable fullnames is set
recipient addresses will be stripped from comments, names etc. quote as well as
quote-as-attachment configure whether responded-to message shall be quoted etc.; setting flipr
will exchange this command with Reply. The command Lreply offers special support for replying
to mailing lists. For more documentation please refer to “On sending mail, and non-interactive
mode”.
This may generate the errors ^ERR-DESTADDRREQ if no receiver has been specified, ^ERR-PERM if
some addressees where rejected by expandaddr, ^ERR-NODATA if no applicable messages have been
given, ^ERR-IO if an I/O error occurs, ^ERR-NOTSUP if a necessary character set conversion
fails, and ^ERR-INVAL for other errors. Occurrence of some of the errors depend on the value
of expandaddr. Any error stops processing of further messages.
replyall Similar to reply, but initiates a group-reply regardless of the value of flipr.
replysender
Similar to Reply, but responds to the sender only regardless of the value of flipr.
Resend Like resend, but does not add any header lines. This is not a way to hide the sender's
identity, but useful for sending a message again to the same recipients.
resend Takes a list of messages and a name, and sends each message to the given, fully expanded
addressee. ‘Resent-From:’ and related header fields are prepended to the new copy of the
message. Saving in record is only performed if record-resent is set.
This may generate the errors ^ERR-DESTADDRREQ if no receiver has been specified, ^ERR-PERM if
the addressee was rejected by expandaddr, ^ERR-NODATA if no applicable messages have been
given, ^ERR-IO if an I/O error occurs, ^ERR-NOTSUP if a necessary character set conversion
fails, and ^ERR-INVAL for other errors. Occurrence of some of the errors depend on the value
of expandaddr. Any error stops processing of further messages.
Respond Same as Reply.
respond Same as reply.
respondall
Same as replyall.
respondsender
Same as replysender.
retain (ret) Superseded by the multiplexer headerpick.
return Only available inside the scope of a defined macro or an account, this will stop evaluation of
any further macro content, and return execution control to the caller. The two optional
parameters must be specified as positive decimal numbers and default to the value 0: the first
argument specifies the signed 32-bit return value (stored in ? [v15 behaviour may differ] and
later extended to signed 64-bit), the second the signed 32-bit error number (stored in !). As
documented for ? a non-0 exit status may cause the program to exit.
Save (S) Similar to save, but saves the messages in a file named after the local part of the sender
of the first message instead of (in record and) taking a filename argument; the variable
outfolder is inspected to decide on the actual storage location.
save (s) Takes a message list and a filename and appends each message in turn to the end of the
file. “Filename transformations” including shell pathname wildcard pattern expansions
(glob(7)) is performed on the filename. If no filename is given, the “secondary mailbox” MBOX
is used. The filename in quotes, followed by the generated character count is echoed on the
user's terminal. If editing a “primary system mailbox” the messages are marked for deletion.
“Filename transformations” will be applied. To filter the saved header fields to the desired
subset use the ‘save’ slot of the white- and blacklisting command headerpick.
savediscard
[Obsolete] Superseded by the multiplexer headerpick.
saveignore
[Obsolete] Superseded by the multiplexer headerpick.
saveretain
[Obsolete] Superseded by the multiplexer headerpick.
search Takes a message specification (list) and displays a header summary of all matching messages, as
via headers. This command is an alias of from. Also see “Specifying messages”.
seen Takes a message list and marks all messages as having been read.
set, unset
(se, [Only new quoting rules] uns) The latter command will delete all given global variables,
or only block-scope local ones if the local command modifier has been used. The former, when
used without arguments, will show all currently known variables, being more verbose if either
of debug or verbose is set. Remarks: this list mode will not automatically link-in known
“ENVIRONMENT” variables, but only explicit addressing will, e.g., via varshow, using a variable
in an if condition or a string passed to echo, explicit setting, as well as some program-
internal use cases.
Otherwise the given variables (and arguments) are set or adjusted. Arguments are of the form
‘name=value’ (no space before or after ‘=’), or plain ‘name’ if there is no value, i.e., a
boolean variable. If a name begins with ‘no’, as in ‘set nosave’, the effect is the same as
invoking the unset command with the remaining part of the variable (‘unset save’). [v15
behaviour may differ] In conjunction with the wysh (or local) command prefix(es) “Shell-style
argument quoting” can be used to quote arguments as necessary. [v15 behaviour may differ]
Otherwise quotation marks may be placed around any part of the assignment statement to quote
blanks or tabs.
When operating in global scope any ‘name’ that is known to map to an environment variable will
automatically cause updates in the program environment (unsetting a variable in the environment
requires corresponding system support) — use the command environ for further environmental
control. If the command modifier local has been used to alter the command to work in block-
scope all variables have values (may they be empty), and creation of names which shadow
“INTERNAL VARIABLES” is actively prevented ([v15 behaviour may differ] shadowing of linked
“ENVIRONMENT” variables and free-form versions of variable chains is not yet detected). Also
see varshow and the sections “INTERNAL VARIABLES” and “ENVIRONMENT”.
? wysh set indentprefix=' -> '
? wysh set atab=$'' aspace=' ' zero=0
shcodec Apply shell quoting rules to the given raw-data arguments. Supports vput (see “Command
modifiers”). The first argument specifies the operation: [+]e[ncode] or d[ecode] cause shell
quoting to be applied to the remains of the line, and expanded away thereof, respectively. If
the former is prefixed with a plus-sign, the quoted result will not be roundtrip enabled, and
thus can be decoded only in the very same environment that was used to perform the encode; also
see mle-quote-rndtrip. If the coding operation fails the error number ! is set to
^ERR-CANCELED, and the unmodified input is used as the result; the error number may change
again due to output or result storage errors.
shell [Only new quoting rules] (sh) Invokes an interactive version of the shell, and returns its exit
status.
shortcut, unshortcut
[Only new quoting rules] Manage the file- or pathname shortcuts as documented for file. The
latter command deletes all shortcuts given as arguments, or all at once when given the asterisk
‘*’. The former shows the list of all currently defined shortcuts if used without arguments,
the target of the given with a single argument. Otherwise arguments are treated as pairs of
shortcuts and their desired expansion, creating new or updating already existing ones.
shift [Only new quoting rules] Shift the positional parameter stack (starting at 1) by the given
number (which must be a positive decimal), or 1 if no argument has been given. It is an error
if the value exceeds the number of positional parameters. If the given number is 0, no action
is performed, successfully. The stack as such can be managed via vpospar. Note this command
will fail in account and hook macros unless the positional parameter stack has been explicitly
created in the current context via vpospar.
show Like type, but performs neither MIME decoding nor decryption, so that the raw message text is
shown.
size (si) Shows the size in characters of each message of the given message-list.
sleep [Only new quoting rules] Sleep for the specified number of seconds (and optionally
milliseconds), by default interruptable. If a third argument is given the sleep will be
uninterruptible, otherwise the error number ! will be set to ^ERR-INTR if the sleep has been
interrupted. The command will fail and the error number will be ^ERR-OVERFLOW if the given
duration(s) overflow the time datatype, and ^ERR-INVAL if the given durations are no valid
integers.
sort, unsort
The latter command disables sorted or threaded mode, returns to normal message order and, if
the header variable is set, displays a header summary. The former command shows the current
sorting criterion when used without an argument, but creates a sorted representation of the
current folder otherwise, and changes the next command and the addressing modes such that they
refer to messages in the sorted order. Message numbers are the same as in regular mode. If
the header variable is set, a header summary in the new order is also displayed. Automatic
folder sorting can be enabled by setting the autosort variable, as in, e.g., ‘set
autosort=thread’. Possible sorting criterions are:
date Sort the messages by their ‘Date:’ field, that is by the time they were sent.
from Sort messages by the value of their ‘From:’ field, that is by the address of the
sender. If the showname variable is set, the sender's real name (if any) is used.
size Sort the messages by their size.
spam [Option] Sort the message by their spam score, as has been classified by spamrate.
status Sort the messages by their message status.
subject Sort the messages by their subject.
thread Create a threaded display.
to Sort messages by the value of their ‘To:’ field, that is by the address of the
recipient. If the showname variable is set, the recipient's real name (if any) is
used.
source [Only new quoting rules] (so) The source command reads commands from the given file. “Filename
transformations” will be applied. If the given expanded argument ends with a vertical bar ‘|’
then the argument will instead be interpreted as a shell command and S-nail will read the
output generated by it. Dependent on the settings of posix and errexit, and also dependent on
whether the command modifier ignerr had been used, encountering errors will stop sourcing of
the given input. [v15 behaviour may differ] Note that source cannot be used from within macros
that execute as folder-hooks or accounts, i.e., it can only be called from macros that were
called.
source_if
[Only new quoting rules] The difference to source (beside not supporting pipe syntax aka shell
command input) is that this command will not generate an error nor warn if the given file
argument cannot be opened successfully.
spamclear
[Option] Takes a list of messages and clears their ‘is-spam’ flag.
spamforget
[Option] Takes a list of messages and causes the spam-interface to forget it has ever used them
to train its Bayesian filter. Unless otherwise noted the ‘is-spam’ flag of the message is
inspected to chose whether a message shall be forgotten to be “ham” or “spam”.
spamham [Option] Takes a list of messages and informs the Bayesian filter of the spam-interface that
they are “ham”. This also clears the ‘is-spam’ flag of the messages in question.
spamrate [Option] Takes a list of messages and rates them using the configured spam-interface, without
modifying the messages, but setting their ‘is-spam’ flag as appropriate; because the spam
rating headers are lost the rate will be forgotten once the mailbox is left. Refer to the
manual section “Handling spam” for the complete picture of spam handling in S-nail.
spamset [Option] Takes a list of messages and sets their ‘is-spam’ flag.
spamspam [Option] Takes a list of messages and informs the Bayesian filter of the spam-interface that
they are “spam”. This also sets the ‘is-spam’ flag of the messages in question.
thread [Obsolete] The same as ‘sort thread’ (consider using a ‘commandalias’ as necessary).
tls [Only new quoting rules] TLS information and management command multiplexer to aid in
“Encrypted network communication”. Commands support vput if so documented (see “Command
modifiers”). The result that is shown in case of errors is always the empty string, errors can
be identified via the error number !. For example, string length overflows are caught and set
! to ^ERR-OVERFLOW. Note this command of course honours the overall TLS configuration.
? vput tls result fingerprint pop3s://ex.am.ple
? echo $?/$!/$^ERRNAME: $result
fingerprint Show the tls-fingerprint-digested fingerprint of the certificate of the given HOST
(‘server:port’, where the port defaults to the HTTPS port, 443). tls-fingerprint is
actively ignored for the runtime of this command. Only available if the term
‘+sockets’ is included in features.
Top Like top but always uses the headerpick ‘type’ slot for white- and blacklisting header fields.
top (to) Takes a message list and types out the first toplines lines of each message on the user's
terminal. Unless a special selection has been established for the ‘top’ slot of the headerpick
command, the only header fields that are displayed are ‘From:’, ‘To:’, ‘CC:’, and ‘Subject:’.
Top will always use the ‘type’ headerpick selection instead. It is possible to apply
compression to what is displayed by setting topsqueeze. Messages are decrypted and converted
to the terminal character set if necessary.
touch (tou) Takes a message list and marks the messages for saving in the “secondary mailbox” MBOX.
S-nail deviates from the POSIX standard with this command, as a following next command will
display the following message instead of the current one.
Type (T) Like type but also displays header fields which would not pass the headerpick selection,
and all visualizable parts of MIME ‘multipart/alternative’ messages.
type (t) Takes a message list and types out each message on the user's terminal. The display of
message headers is selectable via headerpick. For MIME multipart messages, all parts with a
content type of ‘text’, all parts which have a registered MIME type handler (see “HTML mail and
MIME attachments”) which produces plain text output, and all ‘message’ parts are shown, others
are hidden except for their headers. Messages are decrypted and converted to the terminal
character set if necessary. The command mimeview can be used to display parts which are not
displayable as plain text.
unaccount
See account.
unalias (una) See alias.
unanswered
See answered.
unbind See bind.
uncollapse
See collapse.
uncolour See colour.
undefine See define.
undelete See delete.
undraft See draft.
unflag See flag.
unfwdignore
[Obsolete] Superseded by the multiplexer headerpick.
unfwdretain
[Obsolete] Superseded by the multiplexer headerpick.
unignore Superseded by the multiplexer headerpick.
unmimetype
See mimetype.
unmlist See mlist.
unmlsubscribe
See mlsubscribe.
Unread Same as unread.
unread Takes a message list and marks each message as not having been read.
unretain Superseded by the multiplexer headerpick.
unsaveignore
[Obsolete] Superseded by the multiplexer headerpick.
unsaveretain
[Obsolete] Superseded by the multiplexer headerpick.
unset [Only new quoting rules] (uns) See set.
unshortcut
See shortcut.
unsort See short.
unthread [Obsolete] Same as unsort.
urlcodec Perform URL percent codec operations on the raw-data argument, rather according to RFC 3986.
The first argument specifies the operation: e[ncode] or d[ecode] perform plain URL percent en-
and decoding, respectively. p[ath]enc[ode] and p[ath]dec[ode] perform a slightly modified
operation which should be better for pathnames: it does not allow a tilde ‘~’, and will neither
accept hyphen-minus ‘-’ nor dot ‘’. as an initial character. The remains of the line form the
URL data which is to be converted. This is a character set agnostic operation, and it may thus
decode bytes which are invalid in the current ttycharset.
Supports vput (see “Command modifiers”), and manages the error number !. If the coding
operation fails the error number ! is set to ^ERR-CANCELED, and the unmodified input is used as
the result; the error number may change again due to output or result storage errors. [v15
behaviour may differ] This command does not know about URLs beside what is documented. (vexpr
offers a makeprint subcommand, shall the URL be displayed.)
varshow [Only new quoting rules] This command produces the same output as the listing mode of set,
including verboseity adjustments, but only for the given variables.
verify [Option] Takes a message list and verifies each message. If a message is not a S/MIME signed
message, verification will fail for it. The verification process checks if the message was
signed using a valid certificate, if the message sender's email address matches one of those
contained within the certificate, and if the message content has been altered.
version Shows the version and features of S-nail, optionally in a more verbose form which also includes
the build and running system environment. This command supports vput (see “Command
modifiers”).
vexpr [Only new quoting rules] A multiplexer command which offers signed 64-bit numeric calculations,
as well as other, mostly string-based operations. C-style byte string operations are available
via csop. The first argument defines the number, type, and meaning of the remaining arguments.
An empty number argument is treated as 0. Supports vput (see “Command modifiers”). The result
shown in case of errors is ‘-1’ for usage errors and numeric operations, the empty string
otherwise; “soft” errors, like when a search operation failed, will also set the ! error number
to ^ERR-NODATA. Except when otherwise noted numeric arguments are parsed as signed 64-bit
numbers, and errors will be reported in the error number ! as the numeric error ^ERR-RANGE.
Numeric operations work on one or two signed 64-bit integers. Numbers prefixed with ‘0x’ or
‘0X’ are interpreted as hexadecimal (base 16) numbers, whereas ‘0’ indicates octal (base 8),
and ‘0b’ as well as ‘0B’ denote binary (base 2) numbers. It is possible to use any base in
between 2 and 36, inclusive, with the ‘BASE#number’ notation, where the base is given as an
unsigned decimal number, e.g., ‘16#AFFE’ is a different way of specifying a hexadecimal number.
Unsigned interpretation of a number can be enforced by prefixing an ‘u’ (case-insensitively),
e.g., ‘u-110’; this is not necessary for power-of-two bases (2, 4, 8, 16 and 32), which will be
interpreted as unsigned by default, but it still makes a difference regarding overflow
detection and overflow constant. It is possible to enforce signed interpretation by (instead)
prefixing a ‘s’ (case-insensitively). The number sign notation uses a permissive parse mode
and as such supports complicated conditions out of the box:
? wysh set ifs=:;read i;unset ifs;echo $i;vexpr pb 2 10#$i
-009
< -009>
0b1001
One integer is expected by assignment (equals sign ‘=’), which does nothing but parsing the
argument, thus detecting validity and possible overflow conditions, unary not (tilde ‘~’),
which creates the bitwise complement, and unary plus and minus. Two integers are used by
addition (plus sign ‘+’), subtraction (hyphen-minus ‘-’), multiplication (asterisk ‘*’),
division (solidus ‘/’) and modulo (percent sign ‘%’), as well as for the bitwise operators
logical or (vertical bar ‘|’, to be quoted) , bitwise and (ampersand ‘&’, to be quoted) ,
bitwise xor (circumflex ‘^’), the bitwise signed left- and right shifts (‘<<’, ‘>>’), as well
as for the unsigned right shift ‘>>>’.
Another numeric operation is pbase, which takes a number base in between 2 and 36, inclusive,
and will act on the second number given just the same as what equals sign ‘=’ does, but the
number result will be formatted in the base given, as a signed 64-bit number unless unsigned
interpretation of the input number had been forced (with an u prefix).
Numeric operations support a saturated mode via the question mark ‘?’ modifier suffix; the
keyword ‘saturated’ is optional, e.g., ‘+?’, ‘+?satu’, and ‘+?saturated’ are identical. In
saturated mode overflow errors and division and modulo by zero are no longer reported via the
exit status, but the result will linger at the minimum or maximum possible value, instead of
overflowing (or trapping). This is true also for the argument parse step. For the bitwise
shifts, the saturated maximum is 63. Any caught overflow will be reported via the error number
! as ^ERR-OVERFLOW.
? vput vexpr res -? +1 -9223372036854775808
? echo $?/$!/$^ERRNAME:$res
0/75/OVERFLOW:-9223372036854775808
Character set agnostic string functions have no notion of locale settings and character sets.
file-expand Performs the usual “Filename transformations” on its argument.
file-stat, file-lstat Perform the usual “Filename transformations” on the argument, then call
stat(2) and lstat(2), respectively, in order to echo some stat fields such that ‘vput
vexpr v file-stat FILE; eval wysh set $v’ creates accessible variables.
random Generates a random string of the given length, or of PATH_MAX bytes (a constant from
/usr/include) if the value 0 is given; the random string will be base64url encoded
according to RFC 4648, and thus be usable as a (portable) filename.
String operations work, sufficient support provided, according to the active user's locale
encoding and character set (see “Character sets”). Where the question mark ‘?’ modifier suffix
is supported, a case-insensitive operation mode is available; the keyword ‘case’ is optional,
e.g., ‘regex?’ and ‘regex?case’ are identical.
makeprint (One-way) Converts the argument to something safely printable on the terminal.
regex [Option] A string operation that will try to match the first argument with the
regular expression given as the second argument. ‘?’ modifier suffix is supported.
If the optional third argument has been given then instead of showing the match
offset a replacement operation is performed: the third argument is treated as if
specified within dollar-single-quote (see “Shell-style argument quoting”), and any
occurrence of a positional parameter, e.g., 0, 1 etc. is replaced with the according
match group of the regular expression:
? vput vexpr res regex bananarama \
(.*)NanA(.*) '\${1}au\$2'
? echo $?/$!/$^ERRNAME:$res:
1/61/NODATA::
? vput vexpr res regex?case bananarama \
(.*)NanA(.*) '\${1}uauf\$2'
? echo $?/$!/$^ERRNAME:$res:
0/0/NONE:bauauframa:
vpospar [Only new quoting rules] Manage the positional parameter stack (see 1, #, *, @ as well as
shift). If the first argument is ‘clear’, then the positional parameter stack of the current
context, or the global one, if there is none, is cleared. If it is ‘set’, then the remaining
arguments will be used to (re)create the stack, if the parameter stack size limit is excessed
an ^ERR-OVERFLOW error will occur.
If the first argument is ‘quote’, a round-trip capable representation of the stack contents is
created, with each quoted parameter separated from each other with the first character of ifs,
and followed by the first character of if-ws, if that is not empty and not identical to the
first. If that results in no separation at all a space character is used. This mode supports
vput (see “Command modifiers”). I.e., the subcommands ‘set’ and ‘quote’ can be used (in
conjunction with eval) to (re)create an argument stack from and to a single variable
losslessly.
? vpospar set hey, "'you ", world!
? echo $#: <${1}><${2}><${3}>
? vput vpospar x quote
? vpospar clear
? echo $#: <${1}><${2}><${3}>
? eval vpospar set ${x}
? echo $#: <${1}><${2}><${3}>
visual (v) Takes a message list and invokes the VISUAL display editor on each message. Modified
contents are discarded unless the writebackedited variable is set, and are not used unless the
mailbox can be written to and the editor returns a successful exit status. edit can be used
instead for a less display oriented editor.
write (w) For conventional messages the body without all headers is written. The original message is
never marked for deletion in the originating mail folder. The output is decrypted and
converted to its native format as necessary. If the output file exists, the text is appended.
If a message is in MIME multipart format its first part is written to the specified file as for
conventional messages, handling of the remains depends on the execution mode. No special
handling of compressed files is performed.
In interactive mode the user is consecutively asked for the filenames of the processed parts.
For convience saving of each part may be skipped by giving an empty value, the same result as
writing it to /dev/null. Shell piping the part content by specifying a leading vertical bar
‘|’ character for the filename is supported. Other user input undergoes the usual “Filename
transformations”, including shell pathname wildcard pattern expansions (glob(7)) and shell
variable expansion for the message as such, not the individual parts, and contents of the
destination file are overwritten if the file previously existed.
[v15 behaviour may differ] In non-interactive mode any part which does not specify a filename
is ignored, and suspicious parts of filenames of the remaining parts are URL percent encoded
(as via urlcodec) to prevent injection of malicious character sequences, resulting in a
filename that will be written into the current directory. Existing files will not be
overwritten, instead the part number or a dot are appended after a number sign ‘#’ to the name
until file creation succeeds (or fails due to other reasons).
xcall [Only new quoting rules] The sole difference to call is that the new macro is executed in place
of the current one, which will not regain control: all resources of the current macro will be
released first. This implies that any setting covered by localopts will be forgotten and
covered variables will become cleaned up. If this command is not used from within a called
macro it will silently be (a more expensive variant of) call.
xit (x) A synonym for exit.
z [Only new quoting rules] S-nail presents message headers in screenfuls as described under the
headers command. Without arguments this command scrolls to the next window of messages,
likewise if the argument is ‘+’. An argument of ‘-’ scrolls to the last, ‘^’ scrolls to the
first, and ‘$’ to the last screen of messages. A number argument prefixed by ‘+’ or ‘-’
indicates that the window is calculated in relation to the current position, and a number
without a prefix specifies an absolute position.
Z [Only new quoting rules] Similar to z, but scrolls to the next or previous window that contains
at least one ‘new’ or flagged message.
COMMAND ESCAPES
Command escapes are available in compose mode, and are used to perform special functions when composing
messages. Command escapes are only recognized at the beginning of lines, and consist of a trigger
(escape), and a command character. The actual escape character can be set via the internal variable
escape, it defaults to the tilde ‘~’. Otherwise ignored whitespace characters following the escape
character will prevent a possible addition of the command line to the [Option]al history.
Unless otherwise noted all compose mode command escapes ensure proper updates of the variables which
represent the error number ! and the exit status ?. If the variable errexit is set they will, unless
stated otherwise, error out message compose mode and cause a program exit if an operation fails; an
effect equivalent to the command modifier ignerr can however be achieved by placing a hyphen-minus ‘-’
after (possible whitespace following) the escape character. If the [Option]al key bindings are available
it is possible to create bindings specifically for the compose mode.
~~ string
Insert the string of text in the message prefaced by a single ‘~’. (If the escape character
has been changed, that character must be doubled instead.)
~! command
Execute the indicated shell command which follows, replacing unescaped exclamation marks with
the previously executed command if the internal variable bang is set, then return to the
message.
~. End compose mode and send the message. The hooks on-compose-splice-shell and
on-compose-splice, in order, will be called when set, after which, in interactive mode askatend
(leading to askcc, askbcc) and askattach will be checked as well as asksend, after which a set
on-compose-leave hook will be called, autocc and autobcc will be joined in if set, finally a
given message-inject-tail will be incorporated, after which the compose mode is left.
~: S-nail-command or ~_ S-nail-command
Execute the given S-nail command. Not all commands, however, are allowed.
~< filename
Identical to ~r.
~<! command
command is executed using the shell. Its standard output is inserted into the message.
~? [Option] Write a summary of command escapes.
~@ [filename...]
Append or edit the list of attachments. Does not manage the error number ! and the exit status
? (please use ~^ instead if this is a concern). The append mode expects a list of filename
arguments as shell tokens (see “Shell-style argument quoting”; token-separating commas are
ignored, too), to be interpreted as documented for the command line option -a, with the message
number exception as below.
Without filename arguments the attachment list is edited, entry by entry; if a filename is left
empty, that attachment is deleted from the list; once the end of the list is reached either new
attachments may be entered or the session can be quit by committing an empty “new” attachment.
In non-interactive mode or in batch mode (-#) the list of attachments is effectively not edited
but instead recreated; again, an empty input ends list creation.
For all modes, if a given filename solely consists of the number sign ‘#’ followed by either a
valid message number of the currently active mailbox, or by a period ‘.’, referring to the
current message of the active mailbox, the so-called “dot”, then the given message is attached
as a ‘message/rfc822’ MIME message part. The number sign must be quoted to avoid
misinterpretation as a shell comment character.
~| command
Pipe the message text through the specified filter command. If the command gives no output or
terminates abnormally, retain the original text of the message. E.g., the command fmt(1) is
often used as a rejustifying filter.
If the first character of the command is a vertical bar, then the entire message including
header fields is subject to the filter command, e.g., ‘~|| echo Fcc: /tmp/test; cat’ will
prepend a file-carbon-copy message header. Also see ~e, ~v.
~^ cmd [subcmd [arg3 [arg4]]]
Low-level compose mode command which shares semantics with digmsg. Does not manage the error
number ! and the exit status ?: errors are handled via the protocol, and hard errors like I/O
failures cannot be handled. The protocol consists of command lines followed by (a) response
line(s). The first field of the response line represents a status code which specifies whether
a command was successful or not, whether result data is to be expected, and if, the format of
the result data. Error status code lines may optionally contain additional context:
‘210’ Status ok; the remains of the line are the result.
‘211’ Status ok; the rest of the line is optionally used for more status. What follows are
lines of result addresses, terminated by an empty line. All the input, including the
empty line, must be consumed before further commands can be issued. Address lines
consist of two fields, first the plain network address, e.g., ‘bob@exam.ple’,
separated by a single ASCII SP space from the full address as known, e.g., ‘(Lovely)
Bob <bob@exam.ple>’. Non-network addresses use the first field to indicate the type
(hyphen-minus ‘-’ for files, vertical bar ‘|’ for pipes, and number sign ‘#’ for
names which will undergo alias processing) instead, the actual value will be in the
second field.
‘212’ Status ok; the rest of the line is optionally used for more status. What follows are
lines of furtherly unspecified string content, terminated by an empty line. All the
input, including the empty line, must be consumed before further commands can be
issued.
‘500’ Syntax error; invalid command.
‘501’ Syntax error in parameters or arguments.
‘505’ Error: an argument fails verification. For example an invalid address has been
specified (also see expandaddr), or an attempt was made to modify anything in
S-nail's own namespace, or a modifying subcommand has been used on a read-only
message.
‘506’ Error: an otherwise valid argument is rendered invalid due to context. For example,
a second address is added to a header which may consist of a single address only.
If a command indicates failure then the message will have remained unmodified. Most commands
can fail with ‘500’ if required arguments are missing (false command usage). The following
(case-insensitive) commands are supported:
attachment This command allows listing, removal and addition of message attachments. The
second argument specifies the subcommand to apply, one of:
attribute This uses the same search mechanism as described for remove and prints any
known attributes of the first found attachment via ‘212’ upon success or
‘501’ if no such attachment can be found. The attributes are written as
lines of keyword and value tuples, the keyword being separated from the rest
of the line with an ASCII SP space character.
attribute-at This uses the same search mechanism as described for remove-at and is
otherwise identical to attribute.
attribute-set This uses the same search mechanism as described for remove, and will
assign the attribute given as the fourth argument, which is expected to be a
value tuple of keyword and other data, separated by a ASCII SP space or TAB
tabulator character. If the value part is empty, then the given attribute
is removed, or reset to a default value if existence of the attribute is
crucial.
It returns via ‘210’ upon success, with the index of the found attachment
following, ‘505’ for message attachments or if the given keyword is invalid,
and ‘501’ if no such attachment can be found. The following keywords may be
used (case-insensitively):
‘filename’ Sets the filename of the MIME part, i.e., the name that is used
for display and when (suggesting a name for) saving (purposes).
‘content-description’ Associate some descriptive information to the
attachment's content, used in favour of the plain filename by
some MUAs.
‘content-id’ May be used for uniquely identifying MIME entities in several
contexts; this expects a special reference address format as
defined in RFC 2045 and generates a ‘505’ upon address content
verification failure.
‘content-type’ Defines the media type/subtype of the part, which is managed
automatically, but can be overwritten.
‘content-disposition’ Automatically set to the string ‘attachment’.
attribute-set-at This uses the same search mechanism as described for remove-at and is
otherwise identical to attribute-set.
insert Adds the attachment given as the third argument, specified exactly as
documented for the command line option -a, and supporting the message number
extension as documented for ~@. This reports ‘210’ upon success, with the
index of the new attachment following, ‘505’ if the given file cannot be
opened, ‘506’ if an on-the-fly performed character set conversion fails,
otherwise ‘501’ is reported; this is also reported if character set
conversion is requested but not available.
list List all attachments via ‘212’, or report ‘501’ if no attachments exist.
This command is the default command of attachment if no second argument has
been given.
remove This will remove the attachment given as the third argument, and report
‘210’ upon success or ‘501’ if no such attachment can be found. If there
exists any path component in the given argument, then an exact match of the
path which has been used to create the attachment is used directly, but if
only the basename of that path matches then all attachments are traversed to
find an exact match first, and the removal occurs afterwards; if multiple
basenames match, a ‘506’ error occurs. Message attachments are treated as
absolute pathnames.
If no path component exists in the given argument, then all attachments will
be searched for ‘filename=’ parameter matches as well as for matches of the
basename of the path which has been used when the attachment has been
created; multiple matches result in a ‘506’.
remove-at This will interpret the third argument as a number and remove the attachment
at that list position (counting from one!), reporting ‘210’ upon success or
‘505’ if the argument is not a number or ‘501’ if no such attachment exists.
header This command allows listing, inspection, and editing of message headers. Header name
case is not normalized, and case-insensitive comparison should be used when matching
names. The second argument specifies the subcommand to apply, one of:
insert Create a new or an additional instance of the header given in the third
argument, with the header body content as given in the fourth argument (the
remains of the line). It may return ‘501’ if the third argument specifies a
free-form header field name that is invalid, or if body content extraction
fails to succeed, ‘505’ if any extracted address does not pass syntax and/or
security checks or on S-nail namespace violations, and ‘506’ to indicate
prevention of excessing a single-instance header — note that ‘Subject:’ can
be appended to (a space separator will be added automatically first).
‘To:’, ‘Cc:’ or ‘Bcc:’ support the ‘?single’ modifier to enforce treatment
as a single addressee, e.g., ‘header insert To?single: exa, <m@ple>’; the
word ‘single’ is optional.
‘210’ is returned upon success, followed by the name of the header and the
list position of the newly inserted instance. The list position is always 1
for single-instance header fields. All free-form header fields are managed
in a single list.
list Without a third argument a list of all yet existing headers is given via
‘210’; this command is the default command of header if no second argument
has been given. A third argument restricts output to the given header only,
which may fail with ‘501’ if no such field is defined.
remove This will remove all instances of the header given as the third argument,
reporting ‘210’ upon success, ‘501’ if no such header can be found, and
‘505’ on S-nail namespace violations.
remove-at This will remove from the header given as the third argument the instance at
the list position (counting from one!) given with the fourth argument,
reporting ‘210’ upon success or ‘505’ if the list position argument is not a
number or on S-nail namespace violations, and ‘501’ if no such header
instance exists.
show Shows the content of the header given as the third argument. Dependent on
the header type this may respond with ‘211’ or ‘212’; any failure results in
‘501’.
In compose-mode read-only access to optional pseudo headers in the S-nail private
namespace is available:
‘Mailx-Command:’
The name of the command that generates the message, one of ‘forward’,
‘Lreply’, ‘mail’, ‘Reply’, ‘reply’, ‘resend’. This pseudo header always
exists (in compose-mode).
‘Mailx-Raw-To:’
‘Mailx-Raw-Cc:’
‘Mailx-Raw-Bcc:’
Represent the frozen initial state of these headers before any
transformation (e.g., alias, alternates, recipients-in-cc etc.) took place.
‘Mailx-Orig-From:’
‘Mailx-Orig-To:’
‘Mailx-Orig-Cc:’
‘Mailx-Orig-Bcc:’
The values of said headers of the original message which has been addressed
by any of reply, forward, resend.
help, ? Show an abstract of the above commands via ‘211’.
version This command will print the protocol version via ‘210’.
~A The same as ‘~i Sign’.
~a The same as ‘~i sign’.
~b name ...
Add the given names to the list of blind carbon copy recipients.
~c name ...
Add the given names to the list of carbon copy recipients.
~d Read the file specified by the DEAD variable into the message.
~e Invoke the text EDITOR on the message collected so far, then return to compose mode. ~v can be
used for a more display oriented editor, and ~|| offers a pipe-based editing approach.
~F messages
Read the named messages into the message being sent, including all message headers and MIME
parts. If no messages are specified, read in the current message, the “dot”.
~f messages
Read the named messages into the message being sent. If no messages are specified, read in the
current message, the “dot”. Strips down the list of header fields according to the ‘type’
white- and blacklist selection of headerpick. For MIME multipart messages, only the first
displayable part is included.
~H Edit the message header fields ‘From:’, ‘Reply-To:’ and ‘Sender:’ by typing each one in turn
and allowing the user to edit the field. The default values for these fields originate from
the from, reply-to and sender variables.
~h Edit the message header fields ‘To:’, ‘Cc:’, ‘Bcc:’ and ‘Subject:’ by typing each one in turn
and allowing the user to edit the field.
~I variable
Insert the value of the specified variable into the message. The message remains unaltered if
the variable is unset or empty. Any embedded character sequences ‘\t’ horizontal tabulator and
‘\n’ line feed are expanded in posix mode; otherwise the expansion should occur at set time
([v15 behaviour may differ] by using the command modifier wysh).
~i variable
Like ~I, but appends a newline character.
~M messages
Read the named messages into the message being sent, indented by indentprefix. If no messages
are specified, read the current message, the “dot”.
~m messages
Read the named messages into the message being sent, indented by indentprefix. If no messages
are specified, read the current message, the “dot”. Strips down the list of header fields
according to the ‘type’ white- and blacklist selection of headerpick. For MIME multipart
messages, only the first displayable part is included.
~p Display the message collected so far, prefaced by the message header fields and followed by the
attachment list, if any.
~Q Read in the given / current message(s) according to the algorithm of quote.
~q Abort the message being sent, copying it to the file specified by the DEAD variable if save is
set.
~R filename
Identical to ~r, but indent each line that has been read by indentprefix.
~r filename [HERE-delimiter]
Read the named file, object to the usual “Filename transformations”, into the message; if (the
expanded) filename is the hyphen-minus ‘-’ then standard input is used, e.g., for pasting
purposes. Only in this latter mode HERE-delimiter may be given: if it is data will be read in
until the given HERE-delimiter is seen on a line by itself, and encountering EOF is an error;
the HERE-delimiter is a required argument in non-interactive mode; if it is single-quote quoted
then the pasted content will not be expanded, [v15 behaviour may differ] otherwise a future
version of S-nail may perform shell-style expansion on the content.
~s string
Cause the named string to become the current subject field. Newline (NL) and carriage-return
(CR) bytes are invalid and will be normalized to space (SP) characters.
~t name ...
Add the given name(s) to the direct recipient list.
~U messages
Read in the given / current message(s) excluding all headers, indented by indentprefix.
~u messages
Read in the given / current message(s), excluding all headers.
~v Invoke the VISUAL editor on the message collected so far, then return to compose mode. ~e can
be used for a less display oriented editor, and ~|| offers a pipe-based editing approach.
~w filename
Write the message onto the named file, which is object to the usual “Filename transformations”.
If the file exists, the message is appended to it.
~x Same as ~q, except that the message is not saved at all.
INTERNAL VARIABLES
Internal S-nail variables are controlled via the set and unset commands; prefixing a variable name with
the string ‘no’ and calling set has the same effect as using unset: ‘unset crt’ and ‘set nocrt’ do the
same thing. varshow will give more insight on the given variable(s), and set, when called without
arguments, will show a listing of all variables. Both commands support a more verbose listing mode.
Some well-known variables will also become inherited from the program “ENVIRONMENT” implicitly, others
can be imported explicitly with the command environ and henceforth share said properties.
Two different kinds of internal variables exist, and both of which can also form chains. There are
boolean variables, which can only be in one of the two states “set” and “unset”, and value variables with
a(n optional) string value. For the latter proper quoting is necessary upon assignment time, the
introduction of the section “COMMANDS” documents the supported quoting rules.
? wysh set one=val\ 1 two="val 2" \
three='val "3"' four=$'val \'4\''; \
varshow one two three four; \
unset one two three four
Dependent upon the actual option string values may become interpreted as colour names, command
specifications, normal text, etc. They may be treated as numbers, in which case decimal values are
expected if so documented, but otherwise any numeric format and base that is valid and understood by the
vexpr command may be used, too.
There also exists a special kind of string value, the “boolean string”, which must either be a decimal
integer (in which case ‘0’ is false and ‘1’ and any other value is true) or any of the (case-insensitive)
strings ‘off’, ‘no’, ‘n’ and ‘false’ for a false boolean and ‘on’, ‘yes’, ‘y’ and ‘true’ for a true
boolean; a special kind of boolean string is the “quadoption”, which is a boolean string that can
optionally be prefixed with the (case-insensitive) term ‘ask-’, as in ‘ask-yes’, which causes prompting
of the user in interactive mode, with the given boolean as the default value.
Variable chains extend a plain ‘variable’ with ‘variable-HOST’ and ‘variable-USER@HOST’ variants. Here
‘HOST’ will be converted to all lowercase when looked up (but not when the variable is set or unset!),
[Option]ally IDNA converted, and indeed means ‘server:port’ if a ‘port’ had been specified in the
contextual Uniform Resource Locator URL, see “On URL syntax and credential lookup”. Even though this
mechanism is based on URLs no URL percent encoding may be applied to neither of ‘USER’ nor ‘HOST’,
variable chains need to be specified using raw data; the mentioned section contains examples. Variables
which support chains are explicitly documented as such, and S-nail treats the base name of any such
variable special, meaning that users should not create custom names like ‘variable-xyz’ in order to avoid
false classifications and treatment of such variables.
Initial settings
The standard POSIX 2008/Cor 2-2016 mandates the following initial variable settings: noallnet, noappend,
asksub, noaskbcc, noautoprint, nobang, nocmd, nocrt, nodebug, nodot, escape set to ‘~’, noflipr,
nofolder, header, nohold, noignore, noignoreeof, nokeep, nokeepsave, nometoo, nooutfolder, nopage, prompt
set to ‘? ’, noquiet, norecord, save, nosendwait, noshowto, noSign, nosign, toplines set to ‘5’.
However, S-nail has built-in some initial (and some default) settings which (may) diverge, others may
become adjusted by one of the “Resource files”. Displaying the former is accomplished via set: ‘$ s-nail
-:/ -v -Xset -Xx’. In general this implementation sets (and has extended the meaning of) sendwait, and
does not support the noonehop variable – use command line options or mta-arguments to pass options
through to a mta. The default global resource file sets, among others, the variables hold, keep and
keepsave, establishes a default headerpick selection etc., and should thus be taken into account.
Variables
? (Read-only) The exit status of the last command, or the return value of the macro called last.
This status has a meaning in the state machine: in conjunction with errexit any non-0 exit
status will cause a program exit, and in posix mode any error while loading (any of the)
resource files will have the same effect. ignerr, one of the “Command modifiers”, can be used
to instruct the state machine to ignore errors.
! (Read-only) The current error number (errno(3)), which is set after an error occurred; it is
also available via ^ERR, and the error name and documentation string can be queried via
^ERRNAME and ^ERRDOC. [v15 behaviour may differ] This machinery is new and the error number is
only really usable if a command explicitly states that it manages the variable !, for others
errno will be used in case of errors, or ^ERR-INVAL if that is 0: it thus may or may not
reflect the real error. The error number may be set with the command return.
^ (Read-only) This is a multiplexer variable which performs dynamic expansion of the requested
state or condition, of which there are:
^ERR, ^ERRDOC, ^ERRNAME
The number, documentation, and name of the current errno(3), respectively, which is
usually set after an error occurred. The documentation is an [Option], the name is
used if not available. [v15 behaviour may differ] This machinery is new and is
usually reliable only if a command explicitly states that it manages the variable !,
which is effectively identical to ^ERR. Each of those variables can be suffixed with
a hyphen minus followed by a name or number, in which case the expansion refers to
the given error. Note this is a direct mapping of (a subset of) the system error
values:
define work {
eval echo \$1: \$^ERR-$1:\
\$^ERRNAME-$1: \$^ERRDOC-$1
vput vexpr i + "$1" 1
if [ $i -lt 16 ]
\xcall work $i
end
}
call work 0
^ERRQUEUE-COUNT, ^ERRQUEUE-EXISTS
The number of messages present in the [Option]al log queue of errors, and a boolean
which indicates whether the queue is not empty, respectively; both are always 0
unless features indicates ‘+errors’.
* (Read-only) Expands all positional parameters (see 1), separated by the first character of the
value of ifs. [v15 behaviour may differ] The special semantics of the equally named special
parameter of the sh(1) are not yet supported.
@ (Read-only) Expands all positional parameters (see 1), separated by a space character. If
placed in double quotation marks, each positional parameter is properly quoted to expand to a
single parameter again.
# (Read-only) Expands to the number of positional parameters, i.e., the size of the positional
parameter stack in decimal.
0 (Read-only) Inside the scope of a defined and called macro this expands to the name of the
calling macro, or to the empty string if the macro is running from top-level. For the
[Option]al regular expression search and replace operator of vexpr this expands to the entire
matching expression. It represents the program name in global context.
1 (Read-only) Access of the positional parameter stack. All further parameters can be accessed
with this syntax, too, e.g., ‘2’, ‘3’ etc.; positional parameters can be shifted off the stack
by calling shift. The parameter stack contains, e.g., the arguments of a called defined macro,
the matching groups of the [Option]al regular expression search and replace expression of
vexpr, and can be explicitly created or overwritten with the command vpospar.
account (Read-only) Is set to the active account.
add-file-recipients
(Boolean) When file or pipe recipients have been specified, mention them in the corresponding
address fields of the message instead of silently stripping them from their recipient list. By
default such addressees are not mentioned.
allnet (Boolean) Causes only the local part to be evaluated when comparing addresses.
append (Boolean) Causes messages saved in the “secondary mailbox” MBOX to be appended to the end
rather than prepended. This should always be set.
askatend (Boolean) Causes the prompts for ‘Cc:’ and ‘Bcc:’ lists to appear after the message has been
edited.
askattach
(Boolean) If set, S-nail asks an interactive user for files to attach at the end of each
message; An empty line finalizes the list.
askcc (Boolean) Causes the interactive user to be prompted for carbon copy recipients (at the end of
each message if askatend or bsdcompat are set).
askbcc (Boolean) Causes the interactive user to be prompted for blind carbon copy recipients (at the
end of each message if askatend or bsdcompat are set).
asksend (Boolean) Causes the interactive user to be prompted for confirmation to send the message or
reenter compose mode after having been shown an envelope summary. This is by default enabled.
asksign (Boolean)[Option] Causes the interactive user to be prompted if the message is to be signed at
the end of each message. The smime-sign variable is ignored when this variable is set.
asksub (Boolean) Causes S-nail to prompt the interactive user for the subject upon entering compose
mode unless a subject already exists.
attrlist A sequence of characters to display in the ‘attribute’ column of the headline as shown in the
display of headers; each for one type of messages (see “Message states”), with the default
being ‘NUROSPMFAT+-$~’ or ‘NU *HMFAT+-$~’ if the bsdflags variable is set, in the following
order:
‘N’ new.
‘U’ unread but old.
‘R’ new but read.
‘O’ read and old.
‘S’ saved.
‘P’ preserved.
‘M’ mboxed.
‘F’ flagged.
‘A’ answered.
‘T’ draft.
‘+’ [v15 behaviour may differ] start of a (collapsed) thread in threaded mode (see
autosort, thread);
‘-’ [v15 behaviour may differ] an uncollapsed thread in threaded mode; only used in
conjunction with -L.
‘$’ classified as spam.
‘~’ classified as possible spam.
autobcc Specifies a list of recipients to which a blind carbon copy of each outgoing message will be
sent automatically.
autocc Specifies a list of recipients to which a carbon copy of each outgoing message will be sent
automatically.
autocollapse
(Boolean) Causes threads to be collapsed automatically when .Ql thread Ns ed sort mode is
entered (see the collapse command).
autoprint
(Boolean) Enable automatic typeing of a(n existing) “successive” message after delete and
undelete commands, e.g., the message that becomes the new “dot” is shown automatically, as via
dp or dt.
autosort Causes sorted mode (see the sort command) to be entered automatically with the value of this
variable as sorting method when a folder is opened, e.g., ‘set autosort=thread’.
bang (Boolean) Enables the substitution of all not (reverse-solidus) escaped exclamation mark ‘!’
characters by the contents of the last executed command for the ! shell escape command and ~!,
one of the compose mode “COMMAND ESCAPES”. If this variable is not set no reverse solidus
stripping is performed.
bind-timeout
[Option] Terminals generate multi-byte sequences for certain forms of input, for example for
function and other special keys. Some terminals however do not write these multi-byte
sequences as a whole, but byte-by-byte, and the latter is what S-nail actually reads. This
variable specifies the timeout in milliseconds that the MLE (see “On terminal control and line
editor”) waits for more bytes to arrive unless it considers a sequence “complete”. The default
is 200.
bsdcompat
(Boolean) Sets some cosmetical features to traditional BSD style; has the same affect as
setting askatend and all other variables prefixed with ‘bsd’; it also changes the behaviour of
emptystart (which does not exist in BSD).
bsdflags (Boolean) Changes the letters shown in the first column of a header summary to traditional BSD
style.
bsdheadline
(Boolean) Changes the display of columns in a header summary to traditional BSD style.
bsdmsgs (Boolean) Changes some informational messages to traditional BSD style.
bsdorder (Boolean) Causes the ‘Subject:’ field to appear immediately after the ‘To:’ field in message
headers and with the ~h “COMMAND ESCAPES”.
build-cc, build-ld, build-os, build-rest
(Read-only) The build environment, including the compiler, the linker, the operating system
S-nail has been build for, usually taken from uname(1) via ‘uname -s’, and then lowercased, as
well as all the possibly interesting rest of the configuration and build environment. This
information is also available in the verbose output of the command version.
charset-7bit
The value that should appear in the ‘charset=’ parameter of ‘Content-Type:’ MIME header fields
when no character set conversion of the message data was performed. This defaults to US-ASCII,
and the chosen character set should be US-ASCII compatible.
charset-8bit
[Option] The default 8-bit character set that is used as an implicit last member of the
variable sendcharsets. This defaults to UTF-8 if character set conversion capabilities are
available, and to ISO-8859-1 otherwise (unless the operating system environment is known to
always and exclusively support UTF-8 locales), in which case the only supported character set
is ttycharset and this variable is effectively ignored.
charset-unknown-8bit
[Option] RFC 1428 specifies conditions when internet mail gateways shall “upgrade” the content
of a mail message by using a character set with the name ‘unknown-8bit’. Because of the
unclassified nature of this character set S-nail will not be capable to convert this character
set to any other character set. If this variable is set any message part which uses the
character set ‘unknown-8bit’ is assumed to really be in the character set given in the value,
otherwise the (final) value of charset-8bit is used for this purpose.
This variable will also be taken into account if a MIME type (see “The mime.types files”) of a
MIME message part that uses the ‘binary’ character set is forcefully treated as text.
cmd The default value for the pipe command.
colour-disable
(Boolean)[Option] Forcefully disable usage of colours. Also see the section “Coloured
display”.
colour-pager
(Boolean)[Option] Whether colour shall be used for output that is paged through PAGER. Note
that pagers may need special command line options, e.g., less(1) requires the option -R and
lv(1) the option -c in order to support colours. Often doing manual adjustments is unnecessary
since S-nail may perform adjustments dependent on the value of the environment variable PAGER
(see there for more).
contact-mail, contact-web
(Read-only) Addresses for contact per email and web, respectively, e.g., for bug reports,
suggestions, or help regarding S-nail. The former can be used directly: ‘? eval mail
$contact-mail’.
crt In a(n interactive) terminal session, then if this valued variable is set it will be used as a
threshold to determine how many lines the given output has to span before it will be displayed
via the configured PAGER; Usage of the PAGER can be forced by setting this to the value ‘0’,
setting it without a value will deduce the current height of the terminal screen to compute the
threshold (see LINES, screen and stty(1)). [v15 behaviour may differ] At the moment this uses
the count of lines of the message in wire format, which, dependent on the mime-encoding of the
message, is unrelated to the number of display lines. (The software is old and historically
the relation was a given thing.)
customhdr
Define a set of custom headers to be injected into newly composed or forwarded messages. A
custom header consists of the field name followed by a colon ‘:’ and the field content body.
Standard header field names cannot be overwritten by a custom header. Different to the command
line option -C the variable value is interpreted as a comma-separated list of custom headers:
to include commas in header bodies they need to become escaped with reverse solidus ‘\’.
Headers can be managed more freely in compose mode via ~^.
? set customhdr='Hdr1: Body1-1\, Body1-2, Hdr2: Body2'
datefield
Controls the appearance of the ‘%d’ date and time format specification of the headline
variable, that is used, for example, when viewing the summary of headers. If unset, then the
local receiving date is used and displayed unformatted, otherwise the message sending ‘Date:’.
It is possible to assign a strftime(3) format string and control formatting, but embedding
newlines via the ‘%n’ format is not supported, and will result in display errors. The default
is ‘%Y-%m-%d %H:%M’, and also see datefield-markout-older.
datefield-markout-older
Only used in conjunction with datefield. Can be used to create a visible distinction of
messages dated more than a day in the future, or older than six months, a concept comparable to
the -l option of the POSIX utility ls(1). If set to the empty string, then the plain month,
day and year of the ‘Date:’ will be displayed, but a strftime(3) format string to control
formatting can be assigned. The default is ‘%Y-%m-%d’.
debug (Boolean) Enables debug messages and obsoletion warnings, disables the actual delivery of
messages and also implies norecord as well as nosave.
disposition-notification-send
(Boolean)[Option] Emit a ‘Disposition-Notification-To:’ header (RFC 3798) with the message.
This requires the from variable to be set.
dot (Boolean) When dot is set, a period ‘.’ on a line by itself during message input in
(interactive or batch -#) compose mode will be treated as end-of-message (in addition to the
normal end-of-file condition). This behaviour is implied in posix mode with a set ignoreeof.
dotlock-disable
(Boolean)[Option] Disable creation of “dotlock files” for MBOX databases.
dotlock-ignore-error
[Obsolete](Boolean)[Option] Ignore failures when creating “dotlock files”. Please use
dotlock-disable instead.
editalong
If this variable is set then the editor is started automatically when a message is composed in
interactive mode. If the value starts with the letter ‘v’ then this acts as if ~v, otherwise
as if ~e (see “COMMAND ESCAPES”) had been specified. The editheaders variable is implied for
this automatically spawned editor session.
editheaders
(Boolean) When a message is edited while being composed, its header is included in the editable
text.
emptystart
(Boolean) When entering interactive mode S-nail normally writes “No mail for user” and exits
immediately if a mailbox is empty or does not exist. If this variable is set S-nail starts
even with an empty or non-existent mailbox (the latter behaviour furtherly depends upon
bsdcompat, though).
errexit (Boolean) Let each command with a non-0 exit status, including every called macro which returns
a non-0 status, cause a program exit unless prefixed by ignerr (see “Command modifiers”). This
also affects “COMMAND ESCAPES”, but which use a different modifier for ignoring the error.
Please refer to the variable ? for more on this topic.
escape The first character of this value defines the escape character for “COMMAND ESCAPES” in compose
mode. The default value is the character tilde ‘~’. If set to the empty string, command
escapes are disabled.
expandaddr
If unset then file and command pipeline address targets are not allowed, and any such address
will be filtered out, giving a warning message. If set then all possible recipient address
specifications will be accepted, unless the optional value is more specific (also see “On
sending mail, and non-interactive mode”). If the value contains ‘restrict’ then behaviour
equals the former unless in interactive mode, or when tilde commands were enabled explicitly
via -~ or -#, in which case it equals the latter, and thus allows all addressees. ‘restrict’
really acts like ‘restrict,-all,+name,+addr’, so care for ordering issues must be taken.
Indeed the value is interpreted as a comma-separated list of case-insensitive strings. Hard
send errors can be enforced for disallowed address types by setting ‘fail’; by default these
are only filtered out. User name receivers addressing valid local users can be expanded to a
network address (also see hostname) by setting ‘namehostex’. Address targets can be added and
removed with a plus sign ‘+’ or hyphen-minus ‘-’ prefix, respectively: the value ‘all’
addresses all possible specifications, ‘fcc’ whitelists targets specified via ‘Fcc:’ headers
regardless of other settings, ‘file’ file targets (it includes ‘fcc’), ‘pipe’ command pipeline
targets, ‘name’ plain user names left for further expansion by the MTA (implicitly disallowed
for the SMTP based mta), and ‘addr’ network addresses. Targets are interpreted in the given
order, so that ‘restrict,fail,+file,-all,+addr’ will cause hard errors for any non-network
address recipient address unless running interactively or having been started with the option
-~ or -#; in the latter case(s) any address may be used, then.
Historically invalid network addressees were silently stripped off — shall they cause hard
errors instead it must be ensured that ‘failinvaddr’ is an entry of the list (it really acts
like ‘failinvaddr,+addr’). Likewise, ‘domaincheck’ (actually ‘domaincheck,+addr’) compares
address domain names against a whitelist and strips off (‘fail’ for hard errors) addressees
which fail this test; the domain name ‘localhost’ and the non-empty value of hostname (the real
hostname otherwise) are always whitelisted, expandaddr-domaincheck can be set to extend this
list. Finally some address providers (for example -b, -c and all other command line
recipients) will be evaluated as if specified within dollar-single-quotes (see “Shell-style
argument quoting”) if the value list contains the string ‘shquote’.
expandaddr-domaincheck
Can be set to a comma-separated list of domain names which should be whitelisted for the
evaluation of the ‘domaincheck’ mode of expandaddr. IDNA encoding is not automatically
performed, addrcodec can be used to prepare the domain (of an address).
expandargv
Unless this variable is set additional mta (Mail-Transfer-Agent) arguments from the command
line, as can be given after a -- separator, results in a program termination with failure
status. The same can be accomplished by using the special (case-insensitive) value ‘fail’. A
lesser strict variant is the otherwise identical ‘restrict’, which does accept such arguments
in interactive mode, or if tilde commands were enabled explicitly by using one of the command
line options -~ or -#. The empty value will allow unconditional usage.
features (Read-only) String giving a list of optional features. Features are preceded with a plus sign
‘+’ if they are available, with a hyphen-minus ‘-’ otherwise. The output of the command
version includes this information in a more pleasant output.
flipr (Boolean) This setting reverses the meanings of a set of reply commands, turning the lowercase
variants, which by default address all recipients included in the header of a message (reply,
respond, followup) into the uppercase variants, which by default address the sender only
(Reply, Respond, Followup) and vice versa. The commands replysender, respondsender,
followupsender as well as replyall, respondall, followupall are not affected by the current
setting of flipr.
folder The default path under which mailboxes are to be saved: filenames that begin with the plus sign
‘+’ will have the plus sign replaced with the value of this variable if set, otherwise the plus
sign will remain unchanged when doing “Filename transformations”; also see file for more on
this topic, and know about standard imposed implications of outfolder. The value supports a
subset of transformations itself, and if the non-empty value does not start with a solidus ‘/’,
then the value of HOME will be prefixed automatically. Once the actual value is evaluated
first, the internal variable folder-resolved will be updated for caching purposes.
folder-hook-FOLDER, folder-hook
Names a defined macro which will be called whenever a file is opened. The macro will also be
invoked when new mail arrives, but message lists for commands executed from the macro only
include newly arrived messages then. localopts are activated by default in a folder hook,
causing the covered settings to be reverted once the folder is left again.
The specialized form will override the generic one if ‘FOLDER’ matches the file that is opened.
Unlike other folder specifications, the fully expanded name of a folder, without
metacharacters, is used to avoid ambiguities. However, if the mailbox resides under folder
then the usual ‘+’ specification is tried in addition, e.g., if folder is “mail” (and thus
relative to the user's home directory) then /home/usr1/mail/sent will be tried as
‘folder-hook-/home/usr1/mail/sent’ first, but then followed by ‘folder-hook-+sent’.
folder-resolved
(Read-only) Set to the fully resolved path of folder once that evaluation has occurred; rather
internal.
followup-to
(Boolean) Controls whether a ‘Mail-Followup-To:’ header is generated when sending messages to
known mailing lists. The user as determined via from (or, if that contains multiple addresses,
sender) will be placed in there if any list addressee is not a subscribed list. Also see
followup-to-honour and the commands mlist, mlsubscribe, reply and Lreply.
followup-to-add-cc
(Boolean) Controls whether the user will be added to the messages' ‘Cc:’ list in addition to
placing an entry in ‘Mail-Followup-To:’ (see followup-to).
followup-to-honour
Controls whether a ‘Mail-Followup-To:’ header is honoured when group-replying to a message via
reply or Lreply. This is a quadoption; if set without a value it defaults to “yes”, and see
followup-to.
forward-as-attachment
(Boolean) Original messages are normally sent as inline text with the forward command, and only
the first part of a multipart message is included. With this setting enabled messages are sent
as unmodified MIME ‘message/rfc822’ attachments with all of their parts included.
forward-inject-head, forward-inject-tail
The strings to put before and after the text of a message with the forward command,
respectively. The former defaults to ‘-------- Original Message --------\n’. Special format
directives in these strings will be expanded if possible, and if so configured the output will
be folded according to quote-fold; for more please refer to quote-inject-head. These variables
are ignored if the forward-as-attachment variable is set.
from The address (or a list of addresses) to put into the ‘From:’ field of the message header,
quoting RFC 5322: the author(s) of the message, that is, the mailbox(es) of the person(s) or
system(s) responsible for the writing of the message. According to that RFC setting the sender
variable is required if from contains more than one address. Dependent on the context these
addresses are handled as if they were in the list of alternates.
If a file-based MTA is used, then from (or, if that contains multiple addresses, sender) can
nonetheless be enforced to appear as the envelope sender address at the MTA protocol level (the
RFC 5321 reverse-path), either by using the -r command line option (with an empty argument; see
there for the complete picture on this topic), or by setting the internal variable
r-option-implicit.
If the machine's hostname is not valid at the Internet (for example at a dialup machine) then
either this variable or hostname ([v15-compat] a SMTP-based mta adds even more fine-tuning
capabilities with smtp-hostname) have to be set: if so the message and MIME part related unique
ID fields ‘Message-ID:’ and ‘Content-ID:’ will be created (except when disallowed by
message-id-disable or stealthmua).
fullnames
(Boolean) Due to historical reasons comments and name parts of email addresses are removed by
default when sending mail, replying to or forwarding a message. If this variable is set such
stripping is not performed.
fwdheading
[Obsolete] Predecessor of forward-inject-head.
header (Boolean) Causes the header summary to be written at startup and after commands that affect the
number of messages or the order of messages in the current folder. Unless in posix mode a
header summary will also be displayed on folder changes. The command line option -N can be
used to set noheader.
headline A format string to use for the summary of headers. Format specifiers in the given string start
with a percent sign ‘%’ and may be followed by an optional decimal number indicating the field
width — if that is negative, the field is to be left-aligned. Names and addresses are subject
to modifications according to showname and showto. Valid format specifiers are:
‘%%’ A plain percent sign.
‘%>’ “Dotmark”: a space character but for the current message (“dot”), for which it
expands to ‘>’ (dependent on headline-plain).
‘%<’ “Dotmark”: a space character but for the current message (“dot”), for which it
expands to ‘<’ (dependent on headline-plain).
‘%$’ [Option] The spam score of the message, as has been classified via the command
spamrate. Shows only a replacement character if there is no spam support.
‘%a’ Message attribute character (status flag); the actual content can be adjusted by
setting attrlist.
‘%d’ The date found in the ‘Date:’ header of the message when datefield is set (the
default), otherwise the date when the message was received. Formatting can be
controlled by assigning a strftime(3) format string to datefield (and
datefield-markout-older).
‘%e’ The indenting level in ‘thread’ed sort mode.
‘%f’ The address of the message sender.
‘%i’ The message thread tree structure. (Note that this format does not support a field
width, and honours headline-plain.)
‘%L’ Mailing list status: is the addressee of the message a known (mlist) or mlsubscribed
mailing list?
‘%l’ The number of lines of the message, if available.
‘%m’ Message number.
‘%o’ The number of octets (bytes) in the message, if available.
‘%S’ Message subject (if any) in double quotes.
‘%s’ Message subject (if any).
‘%t’ The position in threaded/sorted order.
‘%U’ The value 0 except in an IMAP mailbox, where it expands to the UID of the message.
The default is ‘%>%a%m %-18f %16d %4l/%-5o %i%-s’, or ‘%>%a%m %20-f %16d %3l/%-5o %i%-S’ if
bsdcompat is set. Also see attrlist, headline-plain and headline-bidi.
headline-bidi
Bidirectional text requires special treatment when displaying headers, because numbers (in
dates or for file sizes etc.) will not affect the current text direction, in effect resulting
in ugly line layouts when arabic or other right-to-left text is to be displayed. On the other
hand only a minority of terminals is capable to correctly handle direction changes, so that
user interaction is necessary for acceptable results. Note that extended host system support
is required nonetheless, e.g., detection of the terminal character set is one precondition; and
this feature only works in an Unicode (i.e., UTF-8) locale.
In general setting this variable will cause S-nail to encapsulate text fields that may occur
when displaying headline (and some other fields, like dynamic expansions in prompt) with
special Unicode control sequences; it is possible to fine-tune the terminal support level by
assigning a value: no value (or any value other than ‘1’, ‘2’ and ‘3’) will make S-nail assume
that the terminal is capable to properly deal with Unicode version 6.3, in which case text is
embedded in a pair of U+2068 (FIRST STRONG ISOLATE) and U+2069 (POP DIRECTIONAL ISOLATE)
characters. In addition no space on the line is reserved for these characters.
Weaker support is chosen by using the value ‘1’ (Unicode 6.3, but reserve the room of two
spaces for writing the control sequences onto the line). The values ‘2’ and ‘3’ select Unicode
1.1 support (U+200E, LEFT-TO-RIGHT MARK); the latter again reserves room for two spaces in
addition.
headline-plain
(Boolean) On Unicode (UTF-8) aware terminals enhanced graphical symbols are used by default for
certain entries of headline. If this variable is set only basic US-ASCII symbols will be used.
history-file
[Option] If a line editor is available then this can be set to name the (expandable) path of
the location of a permanent history file; also see history-size.
history-gabby
(Boolean)[Option] Add more entries to the history as is normally done.
history-gabby-persist
(Boolean)[Option] S-nail's own MLE will not save the additional history-gabby entries in
persistent storage unless this variable is set. On the other hand it will not loose the
knowledge of whether a persistent entry was gabby or not. Also see history-file.
history-size
[Option] Setting this variable imposes a limit on the number of concurrent history entries. If
set to the value 0 then no further history entries will be added, and loading and incorporation
of the history-file upon program startup can also be suppressed by doing this. Runtime changes
will not be reflected before the history is saved or loaded (again).
hold (Boolean) This setting controls whether messages are held in the system inbox, and it is set by
default.
hostname Used instead of the value obtained from uname(3) and getaddrinfo(3) as the hostname when
expanding local addresses, e.g., in ‘From:’ (also see “On sending mail, and non-interactive
mode”, e.g., for expansion of addresses that have a valid user-, but no domain name in angle
brackets). If either of from or this variable is set the message and MIME part related unique
ID fields ‘Message-ID:’ and ‘Content-ID:’ will be created (except when disallowed by
message-id-disable or stealthmua). If the [Option]al IDNA support is available (see
idna-disable) variable assignment is aborted when a necessary conversion fails.
Setting it to the empty string will cause the normal hostname to be used, but nonetheless
enables creation of said ID fields. [v15-compat] in conjunction with the built-in SMTP mta
smtp-hostname also influences the results: one should produce some test messages with the
desired combination of hostname, and/or from, sender etc. first.
idna-disable
(Boolean)[Option] Can be used to turn off the automatic conversion of domain names according to
the rules of IDNA (internationalized domain names for applications). Since the IDNA code
assumes that domain names are specified with the ttycharset character set, an UTF-8 locale
charset is required to represent all possible international domain names (before conversion,
that is).
ifs The input field separator that is used ([v15 behaviour may differ] by some functions) to
determine where to split input data.
1. Unsetting is treated as assigning the default value, ‘ \t\n’.
2. If set to the empty value, no field splitting will be performed.
3. If set to a non-empty value, all whitespace characters are extracted and assigned to
the variable ifs-ws.
a. ifs-ws will be ignored at the beginning and end of input. Diverging from POSIX
shells default whitespace is removed in addition, which is owed to the entirely
different line content extraction rules.
b. Each occurrence of a character of ifs will cause field-splitting, any adjacent ifs-ws
characters will be skipped.
ifs-ws (Read-only) Automatically deduced from the whitespace characters in ifs.
ignore (Boolean) Ignore interrupt signals from the terminal while entering messages; instead echo them
as ‘@’ characters and discard the current line.
ignoreeof
(Boolean) Ignore end-of-file conditions (‘control-D’) in compose mode on message input and in
interactive command input. If set an interactive command input session can only be left by
explicitly using one of the commands exit and quit, and message input in compose mode can only
be terminated by entering a period ‘.’ on a line by itself or by using the ~. “COMMAND
ESCAPES”; Setting this implies the behaviour that dot describes in posix mode.
inbox If this is set to a non-empty string it will specify the user's “primary system mailbox”,
overriding MAIL and the system-dependent default, and (thus) be used to replace ‘%’ when doing
“Filename transformations”; also see file for more on this topic. The value supports a subset
of transformations itself.
indentprefix
String used by the ~m, ~M and ~R “COMMAND ESCAPES” and by the quote option for indenting
messages, in place of the POSIX mandated default tabulator character ‘\t’. Also see
quote-chars.
keep (Boolean) If set, an empty “primary system mailbox” file is not removed. Note that, in
conjunction with posix mode any empty file will be removed unless this variable is set. This
may improve the interoperability with other mail user agents when using a common folder
directory, and prevents malicious users from creating fake mailboxes in a world-writable spool
directory. [v15 behaviour may differ] Only local regular (MBOX) files are covered, Maildir and
other mailbox types will never be removed, even if empty.
keep-content-length
(Boolean) When (editing messages and) writing MBOX mailbox files S-nail can be told to keep the
‘Content-Length:’ and ‘Lines:’ header fields that some MUAs generate by setting this variable.
Since S-nail does neither use nor update these non-standardized header fields (which in itself
shows one of their conceptual problems), stripping them should increase interoperability in
between MUAs that work with with same mailbox files. Note that, if this is not set but
writebackedited, as below, is, a possibly performed automatic stripping of these header fields
already marks the message as being modified. [v15 behaviour may differ] At some future time
S-nail will be capable to rewrite and apply an mime-encoding to modified messages, and then
those fields will be stripped silently.
keepsave (Boolean) When a message is saved it is usually discarded from the originating folder when
S-nail is quit. This setting causes all saved message to be retained.
line-editor-cpl-word-breaks
[Option] List of bytes which are used by the mle-complete tabulator completion to decide where
word boundaries exist, by default ‘"'@=;|:’ [v15 behaviour may differ] This mechanism is yet
restricted.
line-editor-disable
(Boolean) Turn off any line editing capabilities (from S-nails POW, see “On terminal control
and line editor” for more).
line-editor-no-defaults
(Boolean)[Option] Do not establish any default key binding.
log-prefix
Error log message prefix string (‘s-nail: ’).
mailbox-display
(Read-only) The name of the current mailbox (file), possibly abbreviated for display purposes.
mailbox-resolved
(Read-only) The fully resolved path of the current mailbox.
mailx-extra-rc
An additional startup file that is loaded as the last of the “Resource files”. Use this file
for commands that are not understood by other POSIX mailx(1) implementations, i.e., mostly
anything which is not covered by “Initial settings”.
markanswered
(Boolean) When a message is replied to and this variable is set, it is marked as having been
answered. See the section “Message states”.
mbox-fcc-and-pcc
(Boolean) By default all file and pipe message receivers (see expandaddr) will be fed valid
MBOX database entry message data (see file, mbox-rfc4155), and existing file targets will
become extended in compliance to RFC 4155. If this variable is unset then a plain standalone
RFC 5322 message will be written, and existing file targets will be overwritten.
mbox-rfc4155
(Boolean) When opening MBOX mailbox databases, and in order to achieve compatibility with old
software, the very tolerant POSIX standard rules for detecting message boundaries (so-called
‘From_’ lines) are used instead of the stricter rules from the standard RFC 4155. This
behaviour can be switched by setting this variable.
This may temporarily be handy when S-nail complains about invalid ‘From_’ lines when opening a
MBOX: in this case setting this variable and re-opening the mailbox in question may correct the
result. If so, copying the entire mailbox to some other file, as in ‘copy * SOME-FILE’, will
perform proper, all-compatible ‘From_’ quoting for all detected messages, resulting in a valid
MBOX mailbox. ([v15 behaviour may differ] The better and non-destructive approach is to re-
encode invalid messages, as if it would be created anew, instead of mangling the ‘From_’ lines;
this requires the structural code changes of the v15 rewrite.) Finally the variable can be
unset again:
define mboxfix {
localopts yes; wysh set mbox-rfc4155;\
wysh File "${1}"; copy * "${2}"
}
call mboxfix /tmp/bad.mbox /tmp/good.mbox
memdebug (Boolean) Internal development variable. (Keeps memory debug enabled even if debug is not
set.)
message-id-disable
(Boolean) By setting this variable the generation of ‘Message-ID:’ and ‘Content-ID:’ message
and MIME part headers can be completely suppressed, effectively leaving this task up to the mta
(Mail-Transfer-Agent) or the SMTP server. Note that according to RFC 5321 a SMTP server is not
required to add this field by itself, so it should be ensured that it accepts messages without
‘Message-ID’.
message-inject-head
A string to put at the beginning of each new message, followed by a newline. [Obsolete] The
escape sequences tabulator ‘\t’ and newline ‘\n’ are understood (use the wysh prefix when
setting the variable(s) instead).
message-inject-tail
A string to put at the end of each new message, followed by a newline. [Obsolete] The escape
sequences tabulator ‘\t’ and newline ‘\n’ are understood (use the wysh prefix when setting the
variable(s) instead). Also see on-compose-leave.
metoo (Boolean) Usually, when an alias expansion contains the sender, the sender is removed from the
expansion. Setting this option suppresses these removals. Note that a set metoo also causes a
‘-m’ option to be passed through to the mta (Mail-Transfer-Agent); though most of the modern
MTAs no longer document this flag, no MTA is known which does not support it (for historical
compatibility).
mime-allow-text-controls
(Boolean) When sending messages, each part of the message is MIME-inspected in order to
classify the ‘Content-Type:’ and ‘Content-Transfer-Encoding:’ (see mime-encoding) that is
required to send this part over mail transport, i.e., a computation rather similar to what the
file(1) command produces when used with the ‘--mime’ option.
This classification however treats text files which are encoded in UTF-16 (seen for HTML files)
and similar character sets as binary octet-streams, forcefully changing any ‘text/plain’ or
‘text/html’ specification to ‘application/octet-stream’: If that actually happens a yet unset
charset MIME parameter is set to ‘binary’, effectively making it impossible for the receiving
MUA to automatically interpret the contents of the part.
If this variable is set, and the data was unambiguously identified as text data at first glance
(by a ‘.txt’ or ‘.html’ file extension), then the original ‘Content-Type:’ will not be
overwritten.
mime-alternative-favour-rich
(Boolean) If this variable is set then rich MIME alternative parts (e.g., HTML) will be
preferred in favour of included plain text versions when displaying messages, provided that a
handler exists which produces output that can be (re)integrated into S-nail's normal visual
display. (E.g., at the time of this writing some newsletters ship their full content only in
the rich HTML part, whereas the plain text part only contains topic subjects.)
mime-counter-evidence
Normally the ‘Content-Type:’ field is used to decide how to handle MIME parts. Some MUAs,
however, do not use “The mime.types files” (also see “HTML mail and MIME attachments”) or a
similar mechanism to correctly classify content, but specify an unspecific MIME type
(‘application/octet-stream’) even for plain text attachments. If this variable is set then
S-nail will try to re-classify such MIME message parts, if possible, for example via a possibly
existing attachment filename. A non-empty value may also be given, in which case a number is
expected, actually a carrier of bits, best specified as a binary value, e.g., ‘0b1111’.
• If bit two is set (counting from 1, decimal 2) then the detected mimetype will be carried
along with the message and be used for deciding which MIME handler is to be used, for
example; when displaying such a MIME part the part-info will indicate the overridden
content-type by showing a plus sign ‘+’.
• If bit three is set (decimal 4) then the counter-evidence is always produced and a positive
result will be used as the MIME type, even forcefully overriding the parts given MIME type.
• If bit four is set (decimal 8) as a last resort the actual content of
‘application/octet-stream’ parts will be inspected, so that data which looks like plain
text can be treated as such. This mode is even more relaxed when data is to be displayed
to the user or used as a message quote (data consumers which mangle data for display
purposes, which includes masking of control characters, for example).
mime-encoding
The MIME ‘Content-Transfer-Encoding’ to use in outgoing text messages and message parts, where
applicable (7-bit clean text messages are without an encoding if possible):
‘8bit’ (Or ‘8b’.) 8-bit transport effectively causes the raw data be passed through
unchanged, but may cause problems when transferring mail messages over channels that
are not ESMTP (RFC 1869) compliant. Also, several input data constructs are not
allowed by the specifications and may cause a different transfer-encoding to be used.
By established rules and popular demand occurrences of ‘^From_’ (see mbox-rfc4155)
will be MBOXO quoted (prefixed with greater-than sign ‘>’) instead of causing a non-
destructive encoding like ‘quoted-printable’ to be chosen, unless context (e.g.,
message signing) requires otherwise.
‘quoted-printable’
(Or ‘qp’.) Quoted-printable encoding is 7-bit clean and has the property that ASCII
characters are passed through unchanged, so that an english message can be read as-
is; it is also acceptable for other single-byte locales that share many characters
with ASCII, like, e.g., ISO-8859-1. The encoding will cause a large overhead for
messages in other character sets: e.g., it will require up to twelve (12) bytes to
encode a single UTF-8 character of four (4) bytes. It is the default encoding.
‘base64’ (Or ‘b64’.) This encoding is 7-bit clean and will always be used for binary data.
This encoding has a constant input:output ratio of 3:4, regardless of the character
set of the input data it will encode three bytes of input to four bytes of output.
This transfer-encoding is not human readable without performing a decoding step.
mime-force-sendout
(Boolean)[Option] Whenever it is not acceptable to fail sending out messages because of non-
convertible character content this variable may be set. It will, as a last resort, classify
the part content as ‘application/octet-stream’. Please refer to the section “Character sets”
for the complete picture of character set conversion in S-nail.
mimetypes-load-control
Can be used to control which of “The mime.types files” are loaded: if the letter ‘u’ is part of
the option value, then the user's personal ~/.mime.types file will be loaded (if it exists);
likewise the letter ‘s’ controls loading of the system wide /etc/mime.types; directives found
in the user file take precedence, letter matching is case-insensitive. If this variable is not
set S-nail will try to load both files. Incorporation of the S-nail-built-in MIME types cannot
be suppressed, but they will be matched last (the order can be listed via mimetype).
More sources can be specified by using a different syntax: if the value string contains an
equals sign ‘=’ then it is instead parsed as a comma-separated list of the described letters
plus ‘f=FILENAME’ pairs; the given filenames will be expanded and loaded, and their content may
use the extended syntax that is described in the section “The mime.types files”. Directives
found in such files always take precedence (are prepended to the MIME type cache).
mta Select an alternate Mail-Transfer-Agent by either specifying the full pathname of an executable
(optionally prefixed with the protocol ‘file://’), or [Option]ally a SMTP aka SUBMISSION
protocol URL, e.g., [v15-compat]
submissions://[user[:password]@]server[:port]
([no v15-compat]: ‘[smtp://]server[:port]’.) The default has been chosen at compile time. MTA
data transfers are always performed in asynchronous child processes, and without supervision
unless either the sendwait or the verbose variable is set. [Option]ally S-nail can take care
of expansion of the usual mta-aliases (aliases(5)).
For testing purposes there is the ‘test’ pseudo-MTA, which dumps to standard output or
optionally to a file, and honours mbox-fcc-and-pcc:
$ echo text | s-nail -:/ -Smta=test -s ubject user@exam.ple
$ </dev/null s-nail -:/ -Smta=test://./xy -s ub user@exam.ple
For a file-based MTA it may be necessary to set mta-argv0 in in order to choose the right
target of a modern mailwrapper(8) environment. It will be passed command line arguments from
several possible sources: from the variable mta-arguments if set, from the command line if
given and the variable expandargv allows their use. Argument processing of the MTA will be
terminated with a -- separator.
The otherwise occurring implicit usage of the following MTA command line arguments can be
disabled by setting the boolean variable mta-no-default-arguments (which will also disable
passing -- to the MTA): -i (for not treating a line with only a dot ‘.’ character as the end of
input), -m (shall the variable metoo be set) and -v (if the verbose variable is set); in
conjunction with the -r command line option S-nail will also (not) pass -f as well as possibly
-F.
[Option]ally S-nail can send mail over SMTP aka SUBMISSION network connections to a single
defined smart host by setting this variable to a SMTP or SUBMISSION URL (see “On URL syntax and
credential lookup”). An authentication scheme can be specified via the variable chain
smtp-auth. Encrypted network connections are [Option]ally available, the section “Encrypted
network communication” should give an overview and provide links to more information on this.
Note that with some mail providers it may be necessary to set the smtp-hostname variable in
order to use a specific combination of from, hostname and mta. Network communication socket
timeouts are configurable, e.g., socket-connect-timeout. All generated network traffic may be
proxied over the SOCKS5 server given in socks-proxy. The following SMTP variants may be used:
• The plain SMTP protocol (RFC 5321) that normally lives on the server port 25 and requires
setting the smtp-use-starttls variable to enter a TLS encrypted session state. Assign a
value like [v15-compat] ‘smtp://[user[:password]@]server[:port]’ ([no v15-compat]
‘smtp://server[:port]’) to choose this protocol.
• The so-called SMTPS which is supposed to live on server port 465 and is automatically TLS
secured. Unfortunately it never became a standardized protocol and may thus not be
supported by your hosts network service database – in fact the port number has already been
reassigned to other protocols!
SMTPS is nonetheless a commonly offered protocol and thus can be chosen by assigning a
value like [v15-compat] ‘smtps://[user[:password]@]server[:port]’ ([no v15-compat]
‘smtps://server[:port]’); due to the mentioned problems it is usually necessary to
explicitly specify the port as ‘:465’, however.
• The SUBMISSION protocol (RFC 6409) lives on server port 587 and is identically to the SMTP
protocol from S-nail's point of view; it requires setting smtp-use-starttls to enter a TLS
secured session state; e.g., [v15-compat] ‘submission://[user[:password]@]server[:port]’.
• The SUBMISSIONS protocol (RFC 8314) that lives on server port 465 and is TLS secured by
default. It can be chosen by assigning a value like [v15-compat]
‘submissions://[user[:password]@]server[:port]’. Due to the problems mentioned for SMTPS
above and the fact that SUBMISSIONS is new and a successor that lives on the same port as
the historical engineering mismanagement named SMTPS, it is usually necessary to explicitly
specify the port as ‘:465’.
mta-aliases
[Option] If set to a valid path pointing to a text file in MTA aliases(5) format, plain ‘name’
(see expandaddr) message receiver names are recursively expanded as a last expansion step,
after the distribution lists which can be created with alias. Constraints on aliases(5)
content support: only local addresses (names) which are valid usernames
(‘[a-z_][a-z0-9_-]*[$]?’) are understood, and [v15 behaviour may differ] ‘:include:/file/name’
directives are not supported. By including ‘-name’ in the setting of expandaddr it can be
asserted that only expanded names (mail addresses) are passed through to the MTA, hard errors
occur otherwise. The file content is cached, but variable as well as file size and
modification time changes will cause an update.
mta-arguments
Arguments to pass through to a file-based mta can be given via this variable, which is parsed
according to “Shell-style argument quoting” into an array of arguments, and which will be
joined onto MTA options from other sources, and then passed individually to the MTA: ‘? wysh
set mta-arguments='-t -X "/tmp/my log"'’.
mta-no-default-arguments
(Boolean) Unless this variable is set S-nail will pass some well known standard command line
options to a file-based mta (Mail-Transfer-Agent), see there for more.
mta-no-receiver-arguments
(Boolean) By default a file-based mta will be passed all receiver addresses on the command
line. This variable can be set to suppress any such argument.
mta-argv0
Many systems use a so-called mailwrapper(8) environment to ensure compatibility with
sendmail(1). This works by inspecting the name that was used to invoke the mail delivery
system. If this variable is set then the mailwrapper (the program that is actually executed
when calling the file-based mta) will treat its contents as that name.
netrc-lookup-USER@HOST, netrc-lookup-HOST, netrc-lookup
(Boolean)[v15-compat][Option] Used to control usage of the user's ~/.netrc file for lookup of
account credentials, as documented in the section “On URL syntax and credential lookup” and for
the command netrc; the section “The .netrc file” documents the file format. Also see
netrc-pipe.
netrc-pipe
[v15-compat][Option] When ~/.netrc is loaded (see netrc and netrc-lookup) then S-nail will read
the output of a shell pipe instead of the user's ~/.netrc file if this variable is set (to the
desired shell command). This can be used to, e.g., store ~/.netrc in encrypted form: ‘? set
netrc-pipe='gpg -qd ~/.netrc.pgp'’.
newfolders
[Option] If this variable has the value ‘maildir’, newly created local folders will be in
Maildir instead of MBOX format.
newmail Checks for new mail in the current folder each time the prompt is shown. A Maildir folder must
be re-scanned to determine if new mail has arrived. If this variable is set to the special
value ‘nopoll’ then a Maildir folder will not be rescanned completely, but only timestamp
changes are detected. Maildir folders are [Option]al.
outfolder
(Boolean) Unless specified as absolute pathnames, causes the filename given in the record
variable and the sender-based filenames for the Copy and Save commands to be interpreted
relative to the directory given in the folder variable rather than relative to the current
directory.
on-account-cleanup-ACCOUNT, on-account-cleanup
Macro hook which will be called once an account is left, as the very last step before unrolling
per-account localopts. This hook is run even in case of fatal errors, and it is advisable to
perform only absolutely necessary actions, like cleaning up alternates, for example. The
specialized form is used in favour of the generic one if found.
on-compose-cleanup
Macro hook which will be called after the message has been sent (or not, in case of failures),
as the very last step before unrolling compose mode localopts. This hook is run even in case
of fatal errors, and it is advisable to perform only absolutely necessary actions, like
cleaning up alternates, for example.
For compose mode hooks that may affect the message content please see on-compose-enter,
on-compose-leave, on-compose-splice. [v15 behaviour may differ] This hook exists because
alias, alternates, commandalias, shortcut, to name a few, are neither covered by localopts nor
by local: changes applied in compose mode will continue to be in effect thereafter.
on-compose-enter, on-compose-leave
Macro hooks which will be called once compose mode is entered, and after composing has been
finished, respectively; the exact order of the steps taken is documented for ~., one of the
“COMMAND ESCAPES”. Context about the message being worked on can be queried via digmsg.
localopts are enabled for these hooks, and changes on variables will be forgotten after the
message has been sent. on-compose-cleanup can be used to perform other necessary cleanup
steps.
Here is an example that injects a signature via message-inject-tail; instead using
on-compose-splice to simply inject the file of desire via ~< or ~<! may be a better approach.
define t_ocl {
vput ! i cat ~/.mysig
if [ $? -eq 0 ]
vput csop message-inject-tail trim-end $i
end
# Alternatively
readctl create ~/.mysig
if [ $? -eq 0 ]
readall i
if [ $? -eq 0 ]
vput csop vexpr message-inject-tail trim-end $i
end
readctl remove ~/.mysig
end
}
set on-compose-leave=t_ocl
on-compose-splice, on-compose-splice-shell
These hooks run once the normal compose mode is finished, but before the on-compose-leave macro
hook is called etc. Both hooks will be executed in a subprocess, with their input and output
connected to S-nail such that they can act as if they would be an interactive user. The
difference in between them is that the latter is a SHELL command, whereas the former is a
normal defined macro, but which is restricted to a small set of commands (the verbose output
of, e.g., list will indicate said capability). localopts are enabled for these hooks (in the
parent process), causing any setting to be forgotten after the message has been sent;
on-compose-cleanup can be used to perform other cleanup as necessary.
During execution of these hooks S-nail will temporarily forget whether it has been started in
interactive mode, (a restricted set of) “COMMAND ESCAPES” will always be available, and for
guaranteed reproducibilities sake escape and ifs will be set to their defaults. The compose
mode command ~^ has been especially designed for scriptability (via these hooks). The first
line the hook will read on its standard input is the protocol version of said command escape,
currently “0 0 1”: backward incompatible protocol changes have to be expected.
Care must be taken to avoid deadlocks and other false control flow: if both involved processes
wait for more input to happen at the same time, or one does not expect more input but the other
is stuck waiting for consumption of its output, etc. There is no automatic synchronization of
the hook: it will not be stopped automatically just because it, e.g., emits ‘~x’. The hooks
will however receive a termination signal if the parent enters an error condition. [v15
behaviour may differ] Protection against and interaction with signals is not yet given; it is
likely that in the future these scripts will be placed in an isolated session, which is
signalled in its entirety as necessary.
define ocs_signature {
read version
echo '~< ~/.mysig' # '~<! fortune pathtofortunefile'
}
set on-compose-splice=ocs_signature
wysh set on-compose-splice-shell=$'\
read version;\
printf "hello $version! Headers: ";\
echo \'~^header list\';\
read status result;\
echo "status=$status result=$result";\
'
define ocsm {
read version
echo Splice protocol version is $version
echo '~^h l'; read hl; vput csop es substring "${hl}" 0 1
if [ "$es" != 2 ]
echoerr 'Cannot read header list'; echo '~x'; xit
endif
if [ "$hl" !%?case ' cc' ]
echo '~^h i cc Diet is your <mirr.or>'; read es;\
vput csop es substring "${es}" 0 1
if [ "$es" != 2 ]
echoerr 'Cannot insert Cc: header'; echo '~x'
# (no xit, macro finishs anyway)
endif
endif
}
set on-compose-splice=ocsm
on-history-addition
This hook will be called if an entry is about to be added to the history of the MLE, as is
documented in “On terminal control and line editor”. It will be called with three arguments:
the first is the name of the input context (see bind), the second whether the command relates
to history-gabby, and the third being the complete command line to be added. The entry will
not be added to history if the hook uses a non-0 return. [v15 behaviour may differ] A future
version will give the expanded command name as the third argument, followed by the tokenized
command line as parsed in the remaining arguments, the first of which is the original
unexpanded command name; i.e., one may do ‘shift 4’ and will then be able to access the
positional parameters as usual via *, #, 1 etc.
on-main-loop-tick
This hook will be called whenever the program's main event loop is about to read the next input
line. Note variable and other changes it performs are not scoped, e.g., via localopts!
on-program-exit
This hook will be called when the program exits, whether via exit or quit, or because the send
mode is done.
on-resend-cleanup
[v15 behaviour may differ] Identical to on-compose-cleanup, but is only triggered by resend.
on-resend-enter
[v15 behaviour may differ] Identical to on-compose-enter, but is only triggered by resend;
currently there is no digmsg support, for example.
page (Boolean) If set, each message feed through the command given for pipe is followed by a
formfeed character ‘\f’.
password-USER@HOST, password-HOST, password
[v15-compat] Variable chain that sets a password, which is used in case none has been given in
the protocol and account-specific URL; as a last resort S-nail will ask for a password on the
user's terminal if the authentication method requires a password. Specifying passwords in a
startup file is generally a security risk; the file should be readable by the invoking user
only.
password-USER@HOST
[no v15-compat] (see the chain above for [v15-compat]) Set the password for ‘USER’ when
connecting to ‘HOST’. If no such variable is defined for a host, the user will be asked for a
password on standard input. Specifying passwords in a startup file is generally a security
risk; the file should be readable by the invoking user only.
piperaw (Boolean) Send messages to the pipe command without performing MIME and character set
conversions.
pipe-TYPE/SUBTYPE
When a MIME message part of type ‘TYPE/SUBTYPE’ (case-insensitive) is displayed or quoted, its
text is filtered through the value of this variable interpreted as a shell command. Note that
only parts which can be displayed inline as plain text (see copiousoutput) are displayed unless
otherwise noted, other MIME parts will only be considered by and for the command mimeview.
The special value question mark ‘?’ forces interpretation of the message part as plain text,
e.g., ‘set pipe-application/xml=?’ will henceforth display XML “as is”. (The same could also
be achieved by adding a MIME type marker with the mimetype command. And [Option]ally MIME type
handlers may be defined via “The Mailcap files” — these directives, copiousoutput has already
been used, should be referred to for further documentation.
The question mark ‘?’ can in fact be used as a trigger character to adjust usage and behaviour
of a following shell command specification more thoroughly by appending more special characters
which refer to further mailcap directives, e.g., the following hypothetical command
specification could be used:
? set pipe-X/Y='?!++=? vim ${MAILX_FILENAME_TEMPORARY}'
‘*’ The command produces plain text to be integrated in S-nails output: copiousoutput.
‘#’ If set the handler will not be invoked when a message is to be quoted, but only when
it will be displayed: x-mailx-noquote.
‘&’ Run the command asynchronously, i.e., without blocking S-nail: x-mailx-async. The
standard output of the command will go to /dev/null.
‘!’ The command must be run on an interactive terminal, S-nail will temporarily release
the terminal to it: needsterminal.
‘+’ Request creation of a zero-sized temporary file, the absolute pathname of which will
be made accessible via the environment variable MAILX_FILENAME_TEMPORARY:
x-mailx-tmpfile. If given twice then the file will be unlinked automatically by
S-nail when the command loop is entered again at latest: x-mailx-tmpfile-unlink; it
is an error to use automatic deletion in conjunction with x-mailx-async.
‘=’ Normally the MIME part content is passed to the handler via standard input; if this
flag is set then the data will instead be written into MAILX_FILENAME_TEMPORARY
(x-mailx-tmpfile-fill), the creation of which is implied; in order to cause automatic
deletion of the temporary file two plus signs ‘++’ still have to be used.
‘?’ To avoid ambiguities with normal shell command content another question mark can be
used to forcefully terminate interpretation of remaining characters. (Any character
not in this list will have the same effect.)
Some information about the MIME part to be displayed is embedded into the environment of the
shell command:
MAILX_CONTENT The MIME content-type of the part, if known, the empty string
otherwise.
MAILX_CONTENT_EVIDENCE If mime-counter-evidence includes the carry-around-bit (2), then this
will be set to the detected MIME content-type; not only then identical
to MAILX_CONTENT otherwise.
MAILX_EXTERNAL_BODY_URL MIME parts of type ‘message/external-body access-type=url’ will store
the access URL in this variable, it is empty otherwise. URL targets
should not be activated automatically, without supervision.
MAILX_FILENAME The filename, if any is set, the empty string otherwise.
MAILX_FILENAME_GENERATED
A random string.
MAILX_FILENAME_TEMPORARY
If temporary file creation has been requested through the command
prefix this variable will be set and contain the absolute pathname of
the temporary file.
pipe-EXTENSION
This is identical to pipe-TYPE/SUBTYPE except that ‘EXTENSION’ (normalized to lowercase using
character mappings of the ASCII charset) names a file extension, e.g., ‘xhtml’. Handlers
registered using this method take precedence.
pop3-auth-USER@HOST, pop3-auth-HOST, pop3-auth
[Option][v15-compat] Variable chain that sets the POP3 authentication method. Supported are
the default ‘plain’, [v15-compat] ‘oauthbearer’ (see “FAQ” entry “But, how about XOAUTH2 /
OAUTHBEARER?”), as well as [v15-compat] ‘external’ and ‘externanon’ for TLS secured connections
which pass a client certificate via tls-config-pairs. There may be the [Option]al method
[v15-compat] ‘gssapi’. ‘externanon’ does not need any user credentials, ‘external’ and
‘gssapi’ need a user, the remains also require a password. ‘externanon’ solely builds upon the
credentials passed via a client certificate, and is usually the way to go since tested servers
do not actually follow RFC 4422, and fail if additional credentials are actually passed.
Unless pop3-no-apop is set the ‘plain’ method will [Option]ally be replaced with APOP if
possible (see there).
pop3-bulk-load-USER@HOST, pop3-bulk-load-HOST, pop3-bulk-load
(Boolean)[Option] When accessing a POP3 server S-nail loads the headers of the messages, and
only requests the message bodies on user request. For the POP3 protocol this means that the
message headers will be downloaded twice. If this variable is set then S-nail will download
only complete messages from the given POP3 server(s) instead.
pop3-keepalive-USER@HOST, pop3-keepalive-HOST, pop3-keepalive
[Option] POP3 servers close the connection after a period of inactivity; the standard requires
this to be at least 10 minutes, but practical experience may vary. Setting this variable to a
numeric value greater than ‘0’ causes a ‘NOOP’ command to be sent each value seconds if no
other operation is performed.
pop3-no-apop-USER@HOST, pop3-no-apop-HOST, pop3-no-apop
(Boolean)[Option] Unless this variable is set the MD5 based ‘APOP’ authentication method will
be used instead of a chosen ‘plain’ pop3-auth when connecting to a POP3 server that advertises
support. The advantage of ‘APOP’ is that only a single packet is sent for the user/password
tuple. (Originally also that the password is not sent in clear text over the wire, but for one
MD5 does not any longer offer sufficient security, and then today transport is almost ever TLS
secured.) Note that pop3-no-apop-HOST requires [v15-compat].
pop3-use-starttls-USER@HOST, pop3-use-starttls-HOST, pop3-use-starttls
(Boolean)[Option] Causes S-nail to issue a ‘STLS’ command to make an unencrypted POP3 session
TLS encrypted. This functionality is not supported by all servers, and is not used if the
session is already encrypted by the POP3S method. Note that pop3-use-starttls-HOST requires
[v15-compat].
posix (Boolean) This flag enables POSIX mode, which changes behaviour of S-nail where that deviates
from standardized behaviour. It will be set implicitly before the “Resource files” are loaded
if the environment variable POSIXLY_CORRECT is set, and adjusting any of those two will be
reflected by the other one implicitly. The following behaviour is covered and enforced by this
mechanism:
• In non-interactive mode, any error encountered while loading resource files during program
startup will cause a program exit, whereas in interactive mode such errors will stop
loading of the currently loaded (stack of) file(s, i.e., recursively). These exits can be
circumvented on a per-command base by using ignerr, one of the “Command modifiers”, for
each command which shall be allowed to fail.
• alternates will replace the list of alternate addresses instead of appending to it. In
addition alternates will only be honoured for any sort of message reply, and for aliases.
• The variable inserting “COMMAND ESCAPES” ~A, ~a, ~I and ~i will expand embedded character
sequences ‘\t’ horizontal tabulator and ‘\n’ line feed. [v15 behaviour may differ] For
compatibility reasons this step will always be performed.
• Upon changing the active file no summary of headers will be displayed even if header is
set.
• Setting ignoreeof implies the behaviour described by dot.
• The variable keep is extended to cover any empty mailbox, not only empty “primary system
mailbox”es: they will be removed when they are left in empty state otherwise.
print-alternatives
(Boolean) When a MIME message part of type ‘multipart/alternative’ is displayed and it contains
a subpart of type ‘text/plain’, other parts are normally discarded. Setting this variable
causes all subparts to be displayed, just as if the surrounding part was of type
‘multipart/mixed’.
prompt The string used as a prompt in interactive mode. Whenever the variable is evaluated the value
is treated as if specified within dollar-single-quotes (see “Shell-style argument quoting”).
This (post-assignment, i.e., second) expansion can be used to embed status information, for
example ?, !, account or mailbox-display.
In order to embed characters which should not be counted when calculating the visual width of
the resulting string, enclose the characters of interest in a pair of reverse solidus escaped
brackets: ‘\[\E[0m\]’; a slot for coloured prompts is also available with the [Option]al
command colour. Prompting may be prevented by setting this to the null string (aka ‘set
noprompt’).
prompt2 This string is used for secondary prompts, but is otherwise identical to prompt. The default
is ‘.. ’.
quiet (Boolean) Suppresses the printing of the version when first invoked.
quote If set a reply message is started with the quoted original message, the lines of which are
prefixed by the value of the variable indentprefix, taking into account quote-chars and
quote-fold. If set to the empty value, the quoted message will be preceded and followed by the
expansions of the values of quote-inject-head and quote-inject-tail, respectively. None of the
headers of the quoted message is included in the quote if the value equals ‘noheading’, and
only the headers selected by the ‘type’ headerpick selection are put above the message body for
‘headers’, whereas all headers and all MIME parts are included for ‘allheaders’. Also see
quote-as-attachment and ~Q, one of the “COMMAND ESCAPES”.
quote-as-attachment
(Boolean) Add the original message in its entirety as a ‘message/rfc822’ MIME attachment when
replying to a message. Note this works regardless of the setting of quote.
quote-chars
Can be set to a string consisting of non-whitespace ASCII characters which shall be treated as
quotation leaders, the default being ‘>|}:’.
quote-fold
[Option] Can be set in addition to indentprefix, and creates a more fancy quotation in that
leading quotation characters (quote-chars) are compressed and overlong lines are folded.
quote-fold can be set to either one, two or three (space separated) numeric values, which are
interpreted as the maximum (goal) and the minimum line length, respectively, in a spirit rather
equal to the fmt(1) program, but line- instead of paragraph-based. The third value is used as
the maximum line length instead of the first if no better break point can be found; it is
ignored unless it is larger than the minimum and smaller than the maximum. If not set
explicitly the minimum will reflect the goal algorithmically. The goal cannot be smaller than
the length of indentprefix plus some additional pad; necessary adjustments take place silently.
quote-inject-head, quote-inject-tail
The strings to put before and after the text of a quoted message, respectively. The former
defaults to ‘%f wrote:\n\n’. Special format directives will be expanded if possible, and if so
configured the output will be folded according to quote-fold. Format specifiers in the given
strings start with a percent sign ‘%’ and expand values of the original message, unless noted
otherwise. Note that names and addresses are not subject to the setting of showto. Valid
format specifiers are:
‘%%’ A plain percent sign.
‘%a’ The address(es) of the sender(s).
‘%d’ The date found in the ‘Date:’ header of the message when datefield is set (the
default), otherwise the date when the message was received. Formatting can be
controlled by assigning a strftime(3) format string to datefield (and
datefield-markout-older).
‘%f’ The full name(s) (name and address, as given) of the sender(s).
‘%i’ The ‘Message-ID:’.
‘%n’ The real name(s) of the sender(s) if there is one and showname allows usage, the
address(es) otherwise.
‘%r’ The senders real name(s) if there is one, the address(es) otherwise.
r-option-implicit
(Boolean) Setting this option evaluates the contents of from (or, if that contains multiple
addresses, sender) and passes the results onto the used (file-based) MTA as described for the
-r option (empty argument case).
recipients-in-cc
(Boolean) When doing a reply, the original ‘From:’ and ‘To:’ are by default merged into the new
‘To:’. If this variable is set, only the original ‘From:’ ends in the new ‘To:’, the rest is
merged into ‘Cc:’.
record Unless this variable is defined, no copies of outgoing mail will be saved. If defined it gives
the pathname, subject to the usual “Filename transformations”, of a folder where all new,
replied-to or forwarded messages are saved: when saving to this folder fails the message is not
sent, but instead saved to DEAD. The standard defines that relative (fully expanded) paths are
to be interpreted relative to the current directory (cwd), to force interpretation relative to
folder outfolder needs to be set in addition.
record-files
(Boolean) If this variable is set the meaning of record will be extended to cover messages
which target only file and pipe recipients (see expandaddr). These address types will not
appear in recipient lists unless add-file-recipients is also set.
record-resent
(Boolean) If this variable is set the meaning of record will be extended to also cover the
resend and Resend commands.
reply-in-same-charset
(Boolean) If this variable is set S-nail first tries to use the same character set of the
original message for replies. If this fails, the mechanism described in “Character sets” is
evaluated as usual.
reply-strings
Can be set to a comma-separated list of (case-insensitive according to ASCII rules) strings
which shall be recognized in addition to the built-in strings as ‘Subject:’ reply message
indicators – built-in are ‘Re:’, which is mandated by RFC 5322, as well as the german ‘Aw:’,
‘Antw:’, and the ‘Wg:’ which often has been seen in the wild; I.e., the separating colon has to
be specified explicitly.
reply-to A list of addresses to put into the ‘Reply-To:’ field of the message header. Members of this
list are handled as if they were in the alternates list.
replyto [Obsolete] Variant of reply-to.
reply-to-honour
Controls whether a ‘Reply-To:’ header is honoured when replying to a message via reply or
Lreply. This is a quadoption; if set without a value it defaults to “yes”.
rfc822-body-from_
(Boolean) This variable can be used to force displaying a so-called ‘From_’ line for messages
that are embedded into an envelope mail via the ‘message/rfc822’ MIME mechanism, for more
visual convenience, also see mbox-rfc4155.
save (Boolean) Enable saving of (partial) messages in DEAD upon interrupt or delivery error.
screen The number of lines that represents a “screenful” of lines, used in headers summary display,
from searching, message topline display and scrolling via z. If this variable is not set
S-nail falls back to a calculation based upon the detected terminal window size and the baud
rate: the faster the terminal, the more will be shown. Overall screen dimensions and pager
usage is influenced by the environment variables COLUMNS and LINES and the variable crt.
searchheaders
(Boolean) Expand message-list specifiers in the form ‘/x:y’ to all messages containing the
substring “y” in the header field ‘x’. The string search is case insensitive.
sendcharsets
[Option] A comma-separated list of character set names that can be used in outgoing internet
mail. The value of the variable charset-8bit is automatically appended to this list of
character sets. If no character set conversion capabilities are compiled into S-nail then the
only supported charset is ttycharset. Also see sendcharsets-else-ttycharset and refer to the
section “Character sets” for the complete picture of character set conversion in S-nail.
sendcharsets-else-ttycharset
(Boolean)[Option] If this variable is set, but sendcharsets is not, then S-nail acts as if
sendcharsets had been set to the value of the variable ttycharset. In effect this combination
passes through the message data in the character set of the current locale encoding: therefore
mail message text will be (assumed to be) in ISO-8859-1 encoding when send from within a
ISO-8859-1 locale, and in UTF-8 encoding when send from within an UTF-8 locale.
The 8-bit fallback charset-8bit never comes into play as ttycharset is implicitly assumed to be
8-bit and capable to represent all files the user may specify (as is the case when no character
set conversion support is available in S-nail and the only supported character set is
ttycharset, see “Character sets”). This might be a problem for scripts which use the suggested
‘LC_ALL=C’ setting, since in this case the character set is US-ASCII by definition, so that it
is better to also override ttycharset, then; and/or do something like the following in the
resource file:
if [ "$LC_ALL" == C ] || [ "$LC_CTYPE" == C ]
unset sendcharsets-else-ttycharset
end
sender An address that is put into the ‘Sender:’ field of outgoing messages, quoting RFC 5322: the
mailbox of the agent responsible for the actual transmission of the message. This field should
normally not be used unless the from field contains more than one address, on which case it is
required. Dependent on the context this address is handled as if it were in the list of
alternates. Also see -r, r-option-implicit.
sendmail [Obsolete] Predecessor of mta.
sendmail-arguments
[Obsolete] Predecessor of mta-arguments.
sendmail-no-default-arguments
[Obsolete](Boolean) Predecessor of mta-no-default-arguments.
sendmail-progname
[Obsolete] Predecessor of mta-argv0.
sendwait Sending messages to the chosen mta or to command-pipe receivers (see “On sending mail, and non-
interactive mode”) will be performed asynchronously. This means that only startup errors of
the respective program will be recognizable, but no delivery errors. Also, no guarantees can
be made as to when the respective program will actually run, as well as to when they will have
produced output.
If this variable is set then child program exit is waited for, and its exit status code is used
to decide about success. Remarks: in conflict with the POSIX standard this variable is built-
in to be initially set. Another difference is that it can have a value, which is interpreted
as a comma-separated list of case-insensitive strings naming specific subsystems for which
synchronousness shall be ensured (only). Possible values are ‘mta’ for mta delivery, and ‘pcc’
for command-pipe receivers.
showlast (Boolean) This setting causes S-nail to start at the last message instead of the first one when
opening a mail folder, as well as with from and headers.
showname (Boolean) Causes S-nail to use the sender's real name instead of the plain address in the
header field summary and in message specifications.
showto (Boolean) Causes the recipient of the message to be shown in the header summary if the message
was sent by the user.
Sign The value backing ~A, one of the “COMMAND ESCAPES”. Also see message-inject-tail,
on-compose-leave and on-compose-splice.
sign The value backing ~a, one of the “COMMAND ESCAPES”. Also see message-inject-tail,
on-compose-leave and on-compose-splice.
signature
[Obsolete] Please use on-compose-splice or on-compose-splice-shell or on-compose-leave and (if
necessary) message-inject-tail instead!
skipemptybody
(Boolean) If an outgoing message does not contain any text in its first or only message part,
do not send it but discard it silently (see also the command line option -E).
smime-ca-dir, smime-ca-file
[Option] Specify the location of trusted CA certificates in PEM (Privacy Enhanced Mail) for the
purpose of verification of S/MIME signed messages. tls-ca-dir documents the necessary
preparation steps to use the former. The set of CA certificates which are built into the TLS
library can be explicitly turned off by setting smime-ca-no-defaults, and further fine-tuning
is possible via smime-ca-flags.
smime-ca-flags
[Option] Can be used to fine-tune behaviour of the X509 CA certificate storage, and the
certificate verification that is used. The actual values and their meanings are documented for
tls-ca-flags.
smime-ca-no-defaults
(Boolean)[Option] Do not load the default CA locations that are built into the used to TLS
library to verify S/MIME signed messages.
smime-cipher-USER@HOST, smime-cipher
[Option] Specifies the cipher to use when generating S/MIME encrypted messages (for the
specified account). RFC 5751 mandates a default of ‘aes128’ (AES-128 CBC). Possible values
are (case-insensitive and) in decreasing cipher strength: ‘aes256’ (AES-256 CBC), ‘aes192’
(AES-192 CBC), ‘aes128’ (AES-128 CBC), ‘des3’ (DES EDE3 CBC, 168 bits; default if ‘aes128’ is
not available) and ‘des’ (DES CBC, 56 bits).
The actually available cipher algorithms depend on the cryptographic library that S-nail uses.
[Option] Support for more cipher algorithms may be available through dynamic loading via, e.g.,
EVP_get_cipherbyname(3) (OpenSSL) if S-nail has been compiled to support this.
smime-crl-dir
[Option] Specifies a directory that contains files with CRLs in PEM format to use when
verifying S/MIME messages.
smime-crl-file
[Option] Specifies a file that contains a CRL in PEM format to use when verifying S/MIME
messages.
smime-encrypt-USER@HOST
[Option] If this variable is set, messages send to the given receiver are encrypted before
sending. The value of the variable must be set to the name of a file that contains a
certificate in PEM format.
If a message is sent to multiple recipients, each of them for whom a corresponding variable is
set will receive an individually encrypted message; other recipients will continue to receive
the message in plain text unless the smime-force-encryption variable is set. It is recommended
to sign encrypted messages, i.e., to also set the smime-sign variable.
smime-force-encryption
(Boolean)[Option] Causes S-nail to refuse sending unencrypted messages.
smime-sign
(Boolean)[Option] S/MIME sign outgoing messages with the user's private key and include the
user's certificate as a MIME attachment. Signing a message enables a recipient to verify that
the sender used a valid certificate, that the email addresses in the certificate match those in
the message header and that the message content has not been altered. It does not change the
message text, and people will be able to read the message as usual. Also see smime-sign-cert,
smime-sign-include-certs and smime-sign-digest.
smime-sign-cert-USER@HOST, smime-sign-cert
[Option] Points to a file in PEM format. For the purpose of signing and decryption this file
needs to contain the user's private key, followed by his certificate.
For message signing ‘USER@HOST’ is always derived from the value of from (or, if that contains
multiple addresses, sender). For the purpose of encryption the recipient's public encryption
key (certificate) is expected; the command certsave can be used to save certificates of signed
messages (the section “Signed and encrypted messages with S/MIME” gives some details). This
mode of operation is usually driven by the specialized form.
When decrypting messages the account is derived from the recipient fields (‘To:’ and ‘Cc:’) of
the message, which are searched for addresses for which such a variable is set. S-nail always
uses the first address that matches, so if the same message is sent to more than one of the
user's addresses using different encryption keys, decryption might fail.
For signing and decryption purposes it is possible to use encrypted keys, and the pseudo-
host(s) ‘USER@HOST.smime-cert-key’ for the private key (and ‘USER@HOST.smime-cert-cert’ for the
certificate stored in the same file) will be used for performing any necessary password lookup,
therefore the lookup can be automated via the mechanisms described in “On URL syntax and
credential lookup”. For example, the hypothetical address ‘bob@exam.ple’ could be driven with
a private key / certificate pair path defined in smime-sign-cert-bob@exam.ple, and needed
passwords would then be looked up via the pseudo hosts ‘bob@exam.ple.smime-cert-key’ (and
‘bob@exam.ple.smime-cert-cert’). To include intermediate certificates, use
smime-sign-include-certs.
smime-sign-digest-USER@HOST, smime-sign-digest
[Option] Specifies the message digestto use when signing S/MIME messages. Please remember that
for this use case ‘USER@HOST’ refers to the variable from (or, if that contains multiple
addresses, sender). The available algorithms depend on the used cryptographic library, but at
least one usable built-in algorithm is ensured as a default. If possible the standard RFC 5751
will be violated by using ‘SHA512’ instead of the mandated ‘SHA1’ due to security concerns.
S-nail will try to add built-in support for the following message digests, names are case-
insensitive: ‘BLAKE2b512’, ‘BLAKE2s256’, ‘SHA3-512’, ‘SHA3-384’, ‘SHA3-256’, ‘SHA3-224’, as
well as the widely available ‘SHA512’, ‘SHA384’, ‘SHA256’, ‘SHA224’, and the proposed insecure
‘SHA1’, finally ‘MD5’. More digests may [Option]ally be available through dynamic loading via,
e.g., the OpenSSL function EVP_get_digestbyname(3).
smime-sign-include-certs-USER@HOST, smime-sign-include-certs
[Option] If used, this is supposed to a consist of a comma-separated list of files, each of
which containing a single certificate in PEM format to be included in the S/MIME message in
addition to the smime-sign-cert certificate. This can be used to include intermediate
certificates of the certificate authority, in order to allow the receiver's S/MIME
implementation to perform a verification of the entire certificate chain, starting from a local
root certificate, over the intermediate certificates, down to the smime-sign-cert. Even though
top level certificates may also be included in the chain, they will not be used for the
verification on the receiver's side.
For the purpose of the mechanisms involved here, ‘USER@HOST’ refers to the content of the
internal variable from (or, if that contains multiple addresses, sender). The pseudo-host
‘USER@HOST.smime-include-certs’ will be used for performing password lookups for these
certificates, shall they have been given one, therefore the lookup can be automated via the
mechanisms described in “On URL syntax and credential lookup”.
smime-sign-message-digest-USER@HOST, smime-sign-message-digest
[Obsolete][Option] Predecessor(s) of smime-sign-digest.
smtp [Obsolete][Option] To use the built-in SMTP transport, specify a SMTP URL in mta. [v15
behaviour may differ] For compatibility reasons a set smtp is used in preference of mta.
smtp-auth-USER@HOST, smtp-auth-HOST, smtp-auth
[Option] Variable chain that controls the SMTP mta authentication method, possible values are
‘none’ ([no v15-compat] default), ‘plain’ ([v15-compat] default), ‘login’, [v15-compat]
‘oauthbearer’ (see “FAQ” entry “But, how about XOAUTH2 / OAUTHBEARER?”) as well as [v15-compat]
‘external’ and ‘externanon’ for TLS secured connections which pass a client certificate via
tls-config-pairs. There may be the [Option]al methods ‘cram-md5’ and ‘gssapi’. ‘none’ and
‘externanon’ do not need any user credentials, ‘external’ and ‘gssapi’ require a user name, and
all other methods require a user name and a password. ‘externanon’ solely builds upon the
credentials passed via a client certificate, and is usually the way to go since tested servers
do not actually follow RFC 4422 aka RFC 4954, and fail if additional credentials are passed.
Also see mta. Note that smtp-auth-HOST is [v15-compat]. ([no v15-compat] Requires
smtp-auth-password and smtp-auth-user. Note for smtp-auth-USER@HOST: may override dependent on
sender address in the variable from.)
smtp-auth-password
[Option][no v15-compat] Sets the global fallback password for SMTP authentication. If the
authentication method requires a password, but neither smtp-auth-password nor a matching
smtp-auth-password-USER@HOST can be found, S-nail will ask for a password on the user's
terminal.
smtp-auth-password-USER@HOST
[no v15-compat] Overrides smtp-auth-password for specific values of sender addresses, dependent
upon the variable from.
smtp-auth-user
[Option][no v15-compat] Sets the global fallback user name for SMTP authentication. If the
authentication method requires a user name, but neither smtp-auth-user nor a matching
smtp-auth-user-USER@HOST can be found, S-nail will ask for a user name on the user's terminal.
smtp-auth-user-USER@HOST
[no v15-compat] Overrides smtp-auth-user for specific values of sender addresses, dependent
upon the variable from.
smtp-hostname
[Option][v15-compat] Normally S-nail uses the variable from to derive the necessary ‘USER@HOST’
information in order to issue a ‘MAIL FROM:<>’ SMTP mta command. Setting smtp-hostname can be
used to use the ‘USER’ from the SMTP account (mta or the user variable chain) and the ‘HOST’
from the content of this variable (or, if that is the empty string, hostname or the local
hostname as a last resort). This often allows using an address that is itself valid but hosted
by a provider other than which (in from) is about to send the message. Setting this variable
also influences generated ‘Message-ID:’ and ‘Content-ID:’ header fields. If the [Option]al
IDNA support is available (see idna-disable) variable assignment is aborted when a necessary
conversion fails.
smtp-use-starttls-USER@HOST, smtp-use-starttls-HOST, smtp-use-starttls
(Boolean)[Option] Causes S-nail to issue a ‘STARTTLS’ command to make an SMTP mta session TLS
encrypted, i.e., to enable transport layer security.
socket-connect-timeout
[Option] A positive number that defines the timeout to wait for establishing a socket
connection before forcing ^ERR-TIMEDOUT.
socks-proxy-USER@HOST, socks-proxy-HOST, socks-proxy
[Option] If this is set to the hostname (SOCKS URL) of a SOCKS5 server then S-nail will proxy
all of its network activities through it. This can be used to proxy SMTP, POP3 etc. network
traffic through the Tor anonymizer, for example. The following would create a local SOCKS
proxy on port 10000 that forwards to the machine ‘HOST’, and from which the network traffic is
actually instantiated:
# Create local proxy server in terminal 1 forwarding to HOST
$ ssh -D 10000 USER@HOST
# Then, start a client that uses it in terminal 2
$ s-nail -Ssocks-proxy-USER@HOST=localhost:10000
spam-interface
[Option] In order to use any of the spam-related commands (like, e.g., spamrate) the desired
spam interface must be defined by setting this variable. Please refer to the manual section
“Handling spam” for the complete picture of spam handling in S-nail. All or none of the
following interfaces may be available:
‘spamc’ Interaction with spamc(1) from the spamassassin(1) (SpamAssassin:
http://spamassassin.apache.org) suite. Different to the generic filter interface
S-nail will automatically add the correct arguments for a given command and has the
necessary knowledge to parse the program's output. A default value for spamc-command
will have been compiled into the S-nail binary if spamc(1) has been found in PATH
during compilation. Shall it be necessary to define a specific connection type
(rather than using a configuration file for that), the variable spamc-arguments can
be used as in, e.g., ‘-d server.example.com -p 783’. It is also possible to specify
a per-user configuration via spamc-user. Note that this interface does not inspect
the ‘is-spam’ flag of a message for the command spamforget.
‘filter’ generic spam filter support via freely configurable hooks. This interface is meant
for programs like bogofilter(1) and requires according behaviour in respect to the
hooks' exit status for at least the command spamrate (‘0’ meaning a message is spam,
‘1’ for non-spam, ‘2’ for unsure and any other return value indicating a hard error);
since the hooks can include shell code snippets diverting behaviour can be
intercepted as necessary. The hooks are spamfilter-ham, spamfilter-noham,
spamfilter-nospam, spamfilter-rate and spamfilter-spam; the manual section “Handling
spam” contains examples for some programs. The process environment of the hooks will
have the variable MAILX_FILENAME_GENERATED set. Note that spam score support for
spamrate is not supported unless the [Option]tional regular expression support is
available and the spamfilter-rate-scanscore variable is set.
spam-maxsize
[Option] Messages that exceed this size will not be passed through to the configured
spam-interface. If unset or 0, the default of 420000 bytes is used.
spamc-command
[Option] The path to the spamc(1) program for the ‘spamc’ spam-interface. Note that the path
is not expanded, but used “as is”. A fallback path will have been compiled into the S-nail
binary if the executable had been found during compilation.
spamc-arguments
[Option] Even though S-nail deals with most arguments for the ‘spamc’ spam-interface
automatically, it may at least sometimes be desirable to specify connection-related ones via
this variable, e.g., ‘-d server.example.com -p 783’.
spamc-user
[Option] Specify a username for per-user configuration files for the ‘spamc’ spam-interface.
If this is set to the empty string then S-nail will use the name of the current user.
spamfilter-ham, spamfilter-noham, spamfilter-nospam, spamfilter-rate, spamfilter-spam
[Option] Command and argument hooks for the ‘filter’ spam-interface. The manual section
“Handling spam” contains examples for some programs.
spamfilter-rate-scanscore
[Option] Because of the generic nature of the ‘filter’ spam-interface spam scores are not
supported for it by default, but if the [Option]nal regular expression support is available
then setting this variable can be used to overcome this restriction. It is interpreted as
follows: first a number (digits) is parsed that must be followed by a semicolon ‘;’ and an
extended regular expression. Then the latter is used to parse the first output line of the
spamfilter-rate hook, and, in case the evaluation is successful, the group that has been
specified via the number is interpreted as a floating point scan score.
ssl-ca-dir-USER@HOST, ssl-ca-dir-HOST, ssl-ca-dir, ssl-ca-file-USER@HOST, ssl-ca-file-HOST, ssl-ca-file
[Obsolete][Option] Predecessors of tls-ca-file, tls-ca-dir.
ssl-ca-flags-USER@HOST, ssl-ca-flags-HOST, ssl-ca-flags
[Obsolete][Option] Predecessor of tls-ca-flags.
ssl-ca-no-defaults-USER@HOST, ssl-ca-no-defaults-HOST, ssl-ca-no-defaults
[Obsolete](Boolean)[Option] Predecessor of tls-ca-no-defaults.
ssl-cert-USER@HOST, ssl-cert-HOST, ssl-cert
[Obsolete][Option] Please use the Certificate slot of tls-config-pairs.
ssl-cipher-list-USER@HOST, ssl-cipher-list-HOST, ssl-cipher-list
[Obsolete][Option] Please use the CipherString slot of tls-config-pairs.
ssl-config-file
[Obsolete][Option] Predecessor of tls-config-file.
ssl-config-module-USER@HOST, ssl-config-module-HOST, ssl-config-module
[Obsolete][Option] Predecessor of tls-config-module.
ssl-config-pairs-USER@HOST, ssl-config-pairs-HOST, ssl-config-pairs
[Obsolete][Option] Predecessor of tls-config-pairs.
ssl-crl-dir, ssl-crl-file
[Obsolete][Option] Predecessors of tls-crl-dir, tls-crl-file.
ssl-curves-USER@HOST, ssl-curves-HOST, ssl-curves
[Obsolete][Option] Please use the Curves slot of tls-config-pairs.
ssl-features
[Obsolete][Option](Read-only) Predecessor of tls-features.
ssl-key-USER@HOST, ssl-key-HOST, ssl-key
[Obsolete][Option] Please use the PrivateKey slot of tls-config-pairs.
ssl-method-USER@HOST, ssl-method-HOST, ssl-method
[Obsolete][Option] Please use the Protocol slot of tls-config-pairs.
ssl-protocol-USER@HOST, ssl-protocol-HOST, ssl-protocol
[Obsolete][Option] Please use the Protocol slot of tls-config-pairs.
ssl-rand-file
[Obsolete][Option] Predecessor of tls-rand-file.
ssl-verify-USER@HOST, ssl-verify-HOST, ssl-verify
[Obsolete][Option] Predecessor of tls-verify.
stealthmua
If only set without an assigned value, then this setting inhibits the generation of the
‘Message-ID:’, ‘Content-ID:’ and ‘User-Agent:’ header fields that include obvious references to
S-nail. There are two pitfalls associated with this: First, the message id of outgoing
messages is not known anymore. Second, an expert may still use the remaining information in
the header to track down the originating mail user agent. If set to the value ‘noagent’, then
the mentioned ‘Message-ID:’ and ‘Content-ID:’ suppression does not occur.
system-mailrc
(Read-only) The compiled in path of the system wide initialization file one of the “Resource
files”: s-nail.rc.
termcap ([Option]) This specifies a comma-separated list of Terminal Information Library (libterminfo,
-lterminfo) and/or Termcap Access Library (libtermcap, -ltermcap) capabilities (see “On
terminal control and line editor”, escape commas with reverse solidus) to be used to overwrite
or define entries. Note this variable will only be queried once at program startup and can
thus only be specified in resource files or on the command line.
String capabilities form ‘cap=value’ pairs and are expected unless noted otherwise. Numerics
have to be notated as ‘cap#number’ where the number is expected in normal decimal notation.
Finally, booleans do not have any value but indicate a true or false state simply by being
defined or not; this indeed means that S-nail does not support undefining an existing boolean.
String capability values will undergo some expansions before use: for one notations like
‘^LETTER’ stand for ‘control-LETTER’, and for clarification purposes ‘\E’ can be used to
specify ‘escape’ (the control notation ‘^[’ could lead to misreadings when a left bracket
follows, which it does for the standard CSI sequence); finally three letter octal sequences, as
in ‘\061’, are supported. To specify that a terminal supports 256-colours, and to define
sequences that home the cursor and produce an audible bell, one might write:
? set termcap='Co#256,home=\E[H,bel=^G'
The following terminal capabilities are or may be meaningful for the operation of the built-in
line editor or S-nail in general:
am auto_right_margin: boolean which indicates if the right margin needs special
treatment; the xenl capability is related, for more see COLUMNS.
clear or cl
clear_screen: clear the screen and home cursor. (Will be simulated via ho plus cd.)
colors or Co
max_colors: numeric capability specifying the maximum number of colours. Note that
S-nail does not actually care about the terminal beside that, but always emits ANSI /
ISO 6429 escape sequences.
cr carriage_return: move to the first column in the current row. The default built-in
fallback is ‘\r’.
cub1 or le
cursor_left: move the cursor left one space (non-destructively). The default built-
in fallback is ‘\b’.
cuf1 or nd
cursor_right: move the cursor right one space (non-destructively). The default
built-in fallback is ‘\E[C’, which is used by most terminals. Less often occur ‘\EC’
and ‘\EOC’.
ed or cd clr_eos: clear the screen.
el or ce clr_eol: clear to the end of line. (Will be simulated via ch plus repetitions of
space characters.)
home or ho
cursor_home: home cursor.
hpa or ch
column_address: move the cursor (to the given column parameter) in the current row.
(Will be simulated via cr plus nd.)
rmcup or te / smcup or ti
exit_ca_mode and enter_ca_mode, respectively: exit and enter the alternative screen
ca-mode, effectively turning S-nail into a fullscreen application. This must be
enabled explicitly by setting termcap-ca-mode.
smkx or ks / rmkx or ke
keypad_xmit and keypad_local, respectively: enable and disable the keypad. This is
always enabled if available, because it seems even keyboards without keypads generate
other key codes for, e.g., cursor keys in that case, and only if enabled we see the
codes that we are interested in.
xenl or xn
eat_newline_glitch: boolean which indicates whether a newline written in the last
column of an auto_right_margin indicating terminal is ignored. With it the full
terminal width is available even on autowrap terminals.
Many more capabilities which describe key-sequences are documented for bind.
termcap-ca-mode
[Option] Allow usage of the exit_ca_mode and enter_ca_mode terminal capabilities, see termcap.
Note this variable will only be queried once at program startup and can thus only be specified
in resource files or on the command line.
termcap-disable
[Option] Disable any interaction with a terminal control library. If set only some generic
fallback built-ins and possibly the content of termcap describe the terminal to S-nail. Note
this variable will only be queried once at program startup and can thus only be specified in
resource files or on the command line.
tls-ca-dir-USER@HOST, tls-ca-dir-HOST, tls-ca-dir, tls-ca-file-USER@HOST, tls-ca-file-HOST, tls-ca-file
[Option] Directory and file, respectively, for pools of trusted CA certificates in PEM (Privacy
Enhanced Mail) format, for the purpose of verification of TLS server certificates. Concurrent
use is possible, the file is loaded once needed first, the directory lookup is performed anew
as a last resort whenever necessary. The CA certificate pool built into the TLS library can be
disabled via tls-ca-no-defaults, further fine-tuning is possible via tls-ca-flags. Note the
directory search variant requires the certificate files to adhere special filename conventions,
please see SSL_CTX_load_verify_locations(3) and verify(1) (or c_rehash(1)).
tls-ca-flags-USER@HOST, tls-ca-flags-HOST, tls-ca-flags
[Option] Can be used to fine-tune behaviour of the X509 CA certificate storage, and the
certificate verification that is used (also see tls-verify). The value is expected to consist
of a comma-separated list of configuration directives, with any intervening whitespace being
ignored. The directives directly map to flags that can be passed to X509_STORE_set_flags(3),
which are usually defined in a file openssl/x509_vfy.h, and the availability of which depends
on the used TLS library version: a directive without mapping is ignored (error log subject to
debug). Directives currently understood (case-insensitively) include:
no-alt-chains
If the initial chain is not trusted, do not attempt to build an alternative chain.
Setting this flag will make OpenSSL certificate verification match that of older
OpenSSL versions, before automatic building and checking of alternative chains has
been implemented; also see trusted-first.
no-check-time
Do not check certificate/CRL validity against current time.
partial-chain
By default partial, incomplete chains which cannot be verified up to the chain top, a
self-signed root certificate, will not verify. With this flag set, a chain succeeds
to verify if at least one signing certificate of the chain is in any of the
configured trusted stores of CA certificates. The OpenSSL manual page
SSL_CTX_load_verify_locations(3) gives some advise how to manage your own trusted
store of CA certificates.
strict Disable workarounds for broken certificates.
trusted-first
Try building a chain using issuers in the trusted store first to avoid problems with
server-sent legacy intermediate certificates. Newer versions of OpenSSL support
alternative chain checking and enable it by default, resulting in the same behaviour;
also see no-alt-chains.
tls-ca-no-defaults-USER@HOST, tls-ca-no-defaults-HOST, tls-ca-no-defaults
(Boolean)[Option] Do not load the default CA locations that are built into the used to TLS
library to verify TLS server certificates.
tls-config-file
[Option] If this variable is set CONF_modules_load_file(3) (if announced via
‘+modules-load-file’ in tls-features) is used to allow resource file based configuration of the
TLS library. This happens once the library is used first, which may also be early during
startup (logged with verbose)! If a non-empty value is given then the given file, after
performing “Filename transformations”, will be used instead of the TLS libraries global
default, and it is an error if the file cannot be loaded. The application name will always be
passed as ‘s-nail’. Some TLS libraries support application-specific configuration via resource
files loaded like this, please see tls-config-module.
tls-config-module-USER@HOST, tls-config-module-HOST, tls-config-module
[Option] If file based application-specific configuration via tls-config-file is available,
announced as ‘+ctx-config’ by tls-features, indicating availability of SSL_CTX_config(3), then,
it becomes possible to use a central TLS configuration file for all programs, including s-nail,
e.g.:
# Register a configuration section for s-nail
s-nail = mailx_master
# The top configuration section creates a relation
# in between dynamic SSL configuration and an actual
# program specific configuration section
[mailx_master]
ssl_conf = mailx_tls_config
# Well that actual program specific configuration section
# now can map individual tls-config-module names to sections,
# e.g., tls-config-module=account_xy
[mailx_tls_config]
account_xy = mailx_account_xy
account_yz = mailx_account_yz
[mailx_account_xy]
MinProtocol = TLSv1.2
Curves=P-521
[mailx_account_yz]
CipherString = TLSv1.2:!aNULL:!eNULL:
MinProtocol = TLSv1.1
Options = Bugs
tls-config-pairs-USER@HOST, tls-config-pairs-HOST, tls-config-pairs
[Option] The value of this variable chain will be interpreted as a comma-separated list of
directive/value pairs. Directives and values need to be separated by equals signs ‘=’, any
whitespace surrounding pair members is removed. Keys are (usually) case-insensitive.
Different to when placing these pairs in a tls-config-module section of a tls-config-file,
commas ‘,’ need to be escaped with a reverse solidus ‘\’ when included in pairs; also
different: if the equals sign ‘=’ is preceded with an asterisk ‘*’ “Filename transformations”
will be performed on the value; it is an error if these fail. Unless proper support is
announced by tls-features (‘+conf-ctx’) only the keys below are supported, otherwise the pairs
will be used directly as arguments to the function SSL_CONF_cmd(3).
Certificate Filename of a TLS client certificate (chain) required by some servers. Fallback
support via SSL_CTX_use_certificate_chain_file(3). “Filename transformations”
are performed. PrivateKey will be set to the same value if not initialized
explicitly. Some services support so-called ‘external’ authentication if a TLS
client certificate was successfully presented during connection establishment
(“connecting is authenticating”).
CipherString A list of ciphers for TLS connections, see ciphers(1). By default no list of
ciphers is set, resulting in a Protocol-specific list of ciphers (the protocol
standards define lists of acceptable ciphers; possibly cramped by the used TLS
library). Fallback support via SSL_CTX_set_cipher_list(3).
Ciphersuites A list of ciphers used for TLSv1.3 connections, see ciphers(1). These will be
joined onto the list of ciphers from CipherString. Available if tls-features
announces ‘+ctx-set-ciphersuites’, as necessary via SSL_CTX_set_ciphersuites(3).
Curves A list of supported elliptic curves, if applicable. By default no curves are
set. Fallback support via SSL_CTX_set1_curves_list(3), if available.
MaxProtocol, MinProtocol
The maximum and minimum supported TLS versions, respectively. Available if
tls-features announces ‘+ctx-set-maxmin-proto’, as necessary via
SSL_CTX_set_max_proto_version(3) and SSL_CTX_set_min_proto_version(3); these
fallbacks use an internal parser which understands the strings ‘SSLv3’, ‘TLSv1’,
‘TLSv1.1’, ‘TLSv1.2’, ‘TLSv1.3’, and the special value ‘None’, which disables the
given limit.
Options Various flags to set. Fallback via SSL_CTX_set_options(3), in which case any
other value but (exactly) ‘Bugs’ results in an error.
PrivateKey Filename of the private key in PEM format of a TLS client certificate. If unset,
the value of Certificate is used. “Filename transformations” are performed.
Fallback via SSL_CTX_use_PrivateKey_file(3).
Protocol The used TLS protocol. If tls-features announces ‘+conf-ctx’ or
‘ctx-set-maxmin-proto’ then using MaxProtocol and MinProtocol is preferable.
Fallback is SSL_CTX_set_options(3), driven via an internal parser which
understands the strings ‘SSLv3’, ‘TLSv1’, ‘TLSv1.1’, ‘TLSv1.2’, ‘TLSv1.3’, and
the special value ‘ALL’. Multiple protocols may be given as a comma-separated
list, any whitespace is ignored, an optional plus sign ‘+’ prefix enables, a
hyphen-minus ‘-’ prefix disables a protocol, so that ‘-ALL, TLSv1.2’ enables only
the TLSv1.2 protocol.
tls-crl-dir, tls-crl-file
[Option] Specify a directory / a file, respectively, that contains a CRL in PEM format to use
when verifying TLS server certificates.
tls-features
[Option](Read-only) This expands to a comma-separated list of the TLS library identity and
optional features. Currently supported identities are ‘libressl’ (LibreSSL) , ‘libssl-0x10100’
(OpenSSL v1.1.x series) and ‘libssl-0x10000’ (elder OpenSSL series, other clones). Optional
features are preceded with a plus sign ‘+’ when available, and with a hyphen-minus ‘-’
otherwise.
Currently known features are ‘conf-ctx’ (tls-config-pairs), ‘ctx-config’ (tls-config-module),
‘ctx-set-ciphersuites’ (Ciphersuites slot of tls-config-pairs), ‘ctx-set-maxmin-proto’
(tls-config-pairs), ‘modules-load-file’ (tls-config-file), and ‘tls-rand-file’ (tls-rand-file).
tls-fingerprint-USER@HOST, tls-fingerprint-HOST, tls-fingerprint
[Option] It is possible to replace the verification of the connection peer certificate against
the entire local pool of CAs (for more see “Encrypted network communication”) with the
comparison against a precalculated certificate message digest, the so-called fingerprint, to be
specified as the used tls-fingerprint-digest. This fingerprint can be calculated with, e.g.,
‘tls fingerprint HOST’.
tls-fingerprint-digest-USER@HOST, tls-fingerprint-digest-HOST, tls-fingerprint-digest
[Option] The message digest to be used when creating TLS certificate fingerprints, the
defaults, if available, in test order, being ‘BLAKE2s256’, ‘SHA256’. For the complete list of
digest algorithms refer to smime-sign-digest.
tls-rand-file
[Option] If tls-features announces ‘+tls-rand-file’ then this will be queried to find a file
with random entropy data which can be used to seed the P(seudo)R(andom)N(umber)G(enerator), see
RAND_load_file(3). The default filename (RAND_file_name(3), normally ~/.rnd) will be used if
this variable is not set or empty, or if the “Filename transformations” fail. Shall seeding
the PRNG have been successful, RAND_write_file(3) will be called to update the entropy.
Remarks: libraries which do not announce this feature seed the PRNG by other means.
tls-verify-USER@HOST, tls-verify-HOST, tls-verify
[Option] Variable chain that sets the action to be performed if an error occurs during TLS
server certificate validation against the specified or default trust stores tls-ca-dir,
tls-ca-file, or the TLS library built-in defaults (unless usage disallowed via
tls-ca-no-defaults), and as fine-tuned via tls-ca-flags. Valid (case-insensitive) values are
‘strict’ (fail and close connection immediately), ‘ask’ (ask whether to continue on standard
input), ‘warn’ (show a warning and continue), ‘ignore’ (do not perform validation). The
default is ‘ask’.
toplines If defined, gives the number of lines of a message to be displayed with the command top; if
unset, the first five lines are printed, if set to 0 the variable screen is inspected. If the
value is negative then its absolute value will be used for unsigned right shifting (see vexpr)
the screen height.
topsqueeze
(Boolean) If set then the top command series will strip adjacent empty lines and quotations.
ttycharset
The character set of the terminal S-nail operates on, and the one and only supported character
set that S-nail can use if no character set conversion capabilities have been compiled into it,
in which case it defaults to ISO-8859-1. Otherwise it defaults to UTF-8. Sufficient locale
support provided the default will be preferably deduced from the locale environment if that is
set (e.g., LC_CTYPE, see there for more); runtime locale changes will be reflected by
ttycharset except during the program startup phase and if -S had been used to freeze the given
value. Refer to the section “Character sets” for the complete picture about character sets.
typescript-mode
(Boolean) A special multiplex variable that disables all variables and settings which result in
behaviour that interferes with running S-nail in script(1), e.g., it sets colour-disable,
line-editor-disable and (before startup completed only) termcap-disable. Unsetting it does not
restore the former state of the covered settings.
umask For a safe-by-default policy the process file mode creation mask umask(2) will be set to ‘0077’
on program startup after the resource files have been loaded, and unless this variable is set.
By assigning this an empty value the active setting will not be changed, otherwise the given
value will be made the new file mode creation mask. Child processes inherit the file mode
creation mask of their parent.
user-HOST, user
[v15-compat] Variable chain that sets a global fallback user name, used in case none has been
given in the protocol and account-specific URL. This variable defaults to the name of the user
who runs S-nail.
v15-compat
Enable upward compatibility with S-nail version 15.0 in respect to which configuration options
are available and how they are handled. If set to a non-empty value the command modifier wysh
is implied and thus enforces “Shell-style argument quoting” over “Old-style argument quoting”
for all commands which support both. This manual uses [v15-compat] and [no v15-compat] to
refer to the new and the old way of doing things, respectively.
verbose (Boolean) This setting, also controllable via the command line option -v, causes S-nail to be
more verbose, e.g., it will display obsoletion warnings and TLS certificate chains. Even
though marked (Boolean) this option may be set up to three times in order to increase the level
of verbosity, higher levels show details of the actual message delivery, protocol conversations
and even variable lookups; a single unset verbose is sufficient to disable verbosity as such.
version, version-date, version-hexnum, version-major, version-minor, version-update
(Read-only) S-nail version information: the first variable is a string with the complete
version identification, the second the release date in ISO 8601 notation without time. The
third is a 32-bit hexadecimal number with the upper 8 bits storing the major, followed by the
minor and update version numbers which occupy 12 bits each. The latter three variables contain
only decimal digits: the major, minor and update version numbers. The output of the command
version will include this information.
writebackedited
If this variable is set messages modified using the edit or visual commands are written back to
the current folder when it is quit; it is only honoured for writable folders in MBOX format,
though. Note that the editor will be pointed to the raw message content in that case, i.e.,
neither MIME decoding nor decryption will have been performed, and proper mbox-rfc4155 ‘From_’
quoting of newly added or edited content is also left as an exercise to the user.
ENVIRONMENT
The term “environment variable” should be considered an indication that these variables are either
standardized as vivid parts of process environments, or that they are commonly found in there. The
process environment is inherited from the sh(1) once S-nail is started, and unless otherwise explicitly
noted handling of the following variables transparently integrates into that of the “INTERNAL VARIABLES”
from S-nail's point of view. This means that, e.g., they can be managed via set and unset, causing
automatic program environment updates (to be inherited by newly created child processes).
In order to integrate other environment variables equally they need to be imported (linked) with the
command environ. This command can also be used to set and unset non-integrated environment variables
from scratch, sufficient system support provided. The following example, applicable to a POSIX shell,
sets the COLUMNS environment variable for S-nail only, and beforehand exports the EDITOR in order to
affect any further processing in the running shell:
$ EDITOR="vim -u ${HOME}/.vimrc"
$ export EDITOR
$ COLUMNS=80 s-nail -R
COLUMNS The user's preferred width in column positions for the terminal screen. Queried and used once
on program startup in interactive or batch (-#) mode, actively managed for child processes and
the MLE (see “On terminal control and line editor”) in interactive mode thereafter. Non-
interactive mode always uses, and the fallback default is a compile-time constant, by default
80 columns. If in batch mode COLUMNS and LINES are both set but not both are usable (empty,
not a number, or 0) at program startup, then the real terminal screen size will be (tried to
be) determined once. (Normally the sh(1) manages these variables, and unsets them for pipe
specifications etc.)
DEAD The name of the (mailbox) file to use for saving aborted messages if save is set; this defaults
to ~/dead.letter. If the variable debug is set no output will be generated, otherwise the
contents of the file will be replaced.
EDITOR Pathname of the text editor to use for the edit command and ~e (see “COMMAND ESCAPES”); VISUAL
is used for a more display oriented editor.
HOME The user's home directory. This variable is only used when it resides in the process
environment. The calling user's home directory will be used instead if this directory does not
exist, is not accessible or cannot be read; it will always be used for the root user. (No test
for being writable is performed to allow usage by non-privileged users within read-only jails,
but dependent on the variable settings this directory is a default write target, e.g., for
DEAD, MBOX and more.)
LC_ALL, LC_CTYPE, LANG
[Option] The (names in lookup order of the) locale(7) (and / or see setlocale(3)) which
indicates the used “Character sets”. Runtime changes trigger automatic updates of the entire
locale system, which includes updating ttycharset (except during startup if the variable has
been frozen via -S).
LINES The user's preferred number of lines for the terminal screen. The behaviour is as described
for COLUMNS, yet the compile-time constant used in non-interactive mode and as a fallback
defaults to 24 (lines).
LISTER Pathname of the directory lister to use in the folders command when operating on local
mailboxes. Default is ls(1) (path search through SHELL).
LOGNAME Upon startup S-nail will actively ensure that this variable refers to the name of the user who
runs S-nail, in order to be able to pass a verified name to any newly created child process.
MAIL Is used as the user's “primary system mailbox” unless inbox is set. This is assumed to be an
absolute pathname. If this environmental fallback is also not set, a built-in compile-time
default is used.
MAILCAPS [Option] Overrides the default path search for “The Mailcap files”, which is defined in the
standard RFC 1524 as ‘~/.mailcap:/etc/mailcap:/usr/etc/mailcap:/usr/local/etc/mailcap’. (‐
S-nail makes it a configuration option, however.) Note this is not a search path, but a path
search.
MAILRC Is used as a startup file instead of ~/.mailrc if set. In order to avoid side-effects from
configuration files scripts should either set this variable to /dev/null or the -: command line
option should be used.
MAILX_NO_SYSTEM_RC
If this variable is set then reading of s-nail.rc (aka system-mailrc) at startup is inhibited,
i.e., the same effect is achieved as if S-nail had been started up with the option -: (and
according argument) or -n. This variable is only used when it resides in the process
environment.
MBOX The name of the user's “secondary mailbox” file. A logical subset of the special “Filename
transformations” (also see file) are supported. The default is ~/mbox. Traditionally this
MBOX is used as the file to save messages from the “primary system mailbox” that have been
read. Also see “Message states”.
NETRC [v15-compat][Option] This variable overrides the default location of the user's ~/.netrc file.
PAGER Pathname of the program to use for backing the command more, and when the crt variable enforces
usage of a pager for output. The default paginator is more(1) (path search through SHELL).
S-nail inspects the contents of this variable: if its contains the string “less” then a non-
existing environment variable LESS will be set to ‘Ri’, likewise for “lv” LV will optionally be
set to ‘-c’. Alse see colour-pager.
PATH A colon-separated list of directories that is searched by the shell when looking for commands,
e.g., ‘/bin:/usr/bin:/usr/local/bin’.
POSIXLY_CORRECT
This variable is automatically looked for upon startup, see posix for more.
SHELL The shell to use for the commands !, shell, the ~! “COMMAND ESCAPES” and when starting
subprocesses. A default shell is used if this environment variable is not defined.
SOURCE_DATE_EPOCH
Specifies a time in seconds since the Unix epoch (1970-01-01) to be used in place of the
current time. This variable is looked up upon program startup, and its existence will switch
S-nail to a reproducible mode (https://reproducible-builds.org) which uses deterministic random
numbers, a special fixated pseudo LOGNAME and more. This operation mode is used for
development and by software packagers. [v15 behaviour may differ] Currently an invalid setting
is only ignored, rather than causing a program abortion.
$ SOURCE_DATE_EPOCH=`date +%s` s-nail
TERM [Option] The terminal type for which output is to be prepared. For extended colour and font
control please refer to “Coloured display”, and for terminal management in general to “On
terminal control and line editor”.
TMPDIR Except for the root user this variable defines the directory for temporary files to be used
instead of /tmp (or the given compile-time constant) if set, existent, accessible as well as
read- and writable. This variable is only used when it resides in the process environment, but
S-nail will ensure at startup that this environment variable is updated to contain a usable
temporary directory.
USER Identical to LOGNAME (see there), but this variable is not standardized, should therefore not
be used, and is only corrected if already set.
VISUAL Pathname of the text editor to use for the visual command and ~v (see “COMMAND ESCAPES”);
EDITOR is used for a less display oriented editor.
FILES
~/.mailrc
User-specific file giving initial commands, one of the “Resource files”. The actual value is
read from MAILRC.
s-nail.rc
System wide initialization file, one of the “Resource files”. The actual value is read from
system-mailrc.
~/.mailcap
[Option] Personal MIME type handler definition file, see “The Mailcap files”. This location is
part of the RFC 1524 standard search path, which is a configuration option and can be
overridden via MAILCAPS.
/etc/mailcap
[Option] System wide MIME type handler definition file, see “The Mailcap files”. This location
is part of the RFC 1524 standard search path, which is a configuration option and can be
overridden via
~/mbox The default value for MBOX.
~/.mime.types
Personal MIME types, see “The mime.types files”.
/etc/mime.types
System wide MIME types, see “The mime.types files”.
~/.netrc [v15-compat][Option] The default location of the user's .netrc file – the section “The .netrc
file” documents the file format. The actually used path can be overridden via NETRC.
/dev/null
The data sink null(4).
Resource files
Upon startup S-nail reads in several resource files, in order:
s-nail.rc
System wide initialization file (system-mailrc). Reading of this file can be suppressed,
either by using the -: (and according argument) or -n command line options, or by setting the
“ENVIRONMENT” variable MAILX_NO_SYSTEM_RC.
~/.mailrc
File giving initial commands. A different file can be chosen by setting the “ENVIRONMENT”
variable MAILRC. Reading of this file can be suppressed with the -: command line option.
mailx-extra-rc
Defines a startup file to be read after all other resource files. It can be used to specify
settings that are not understood by other mailx(1) implementations, for example. This variable
is only honoured when defined in a resource file, e.g., it is one of the “INTERNAL VARIABLES”.
The content of these files is interpreted as follows:
• The whitespace characters space, tabulator and newline, as well as those defined by the variable ifs,
are removed from the beginning and end of input lines.
• Empty lines are ignored.
• Any other line is interpreted as a command. It may be spread over multiple input lines if the
newline character is “escaped” by placing a reverse solidus character ‘\’ as the last character of
the line; whereas any leading whitespace of follow lines is ignored, trailing whitespace before a
escaped newline remains in the input.
• If the line (content) starts with the number sign ‘#’ then it is a comment-command and also ignored.
(The comment-command is a real command, which does nothing, and therefore the usual follow lines
mechanism applies!)
Unless S-nail is about to enter interactive mode syntax errors that occur while loading these files are
treated as errors and cause program exit. More files with syntactically equal content can be sourceed.
The following, saved in a file, would be an examplary content:
# This line is a comment command. And y\
es, it is really continued here.
set debug \
verbose
set editheaders
The mime.types files
As stated in “HTML mail and MIME attachments” S-nail needs to learn about MIME (Multipurpose Internet
Mail Extensions) media types in order to classify message and attachment content. One source for them
are mime.types files, the loading of which can be controlled by setting the variable
mimetypes-load-control. Another is the command mimetype, which also offers access to S-nails MIME type
cache. mime.types files have the following syntax:
type/subtype extension [extension ...]
# E.g.: text/html html htm
where ‘type/subtype’ define the MIME media type, as standardized in RFC 2046: ‘type’ is used to declare
the general type of data, while the ‘subtype’ specifies a specific format for that type of data. One or
multiple filename ‘extension’s, separated by whitespace, can be bound to the media type format. Comments
may be introduced anywhere on a line with a number sign ‘#’, causing the remaining line to be discarded.
S-nail also supports an extended, non-portable syntax in especially crafted files, which can be loaded
via the alternative value syntax of mimetypes-load-control, and prepends an optional ‘type-marker’:
[type-marker ]type/subtype extension [extension ...]
The following type markers are supported:
? Treat message parts with this content as plain text.
?t The same as plain ?.
?h Treat message parts with this content as HTML tagsoup. If the [Option]al HTML-tagsoup-to-text
converter is not available treat the content as plain text instead.
?H Likewise ?h, but instead of falling back to plain text require an explicit content handler to
be defined.
?q If no handler can be found a text message is displayed which says so. This can be annoying,
for example signatures serve a contextual purpose, their content is of no use by itself. This
marker will avoid displaying the text message.
Further reading: for sending messages: mimetype, mime-allow-text-controls, mimetypes-load-control. For
reading etc. messages: “HTML mail and MIME attachments”, “The Mailcap files”, mimetype,
mime-counter-evidence, mimetypes-load-control, pipe-TYPE/SUBTYPE, pipe-EXTENSION.
The Mailcap files
This feature is not available in v14.9.0, sorry! RFC 1524 defines a “User Agent Configuration Mechanism”
which S-nail [Option]ally supports (see “HTML mail and MIME attachments”). It defines a file format to
be used to inform mail user agent programs about the locally-installed facilities for handling various
data formats, i.e., about commands and how they can be used to display, edit et cetera MIME part
contents, as well as a default path search that includes multiple possible locations of “mailcap” files
and the MAILCAPS environment variable that can be used to overwrite that (repeating here that it is not a
search path, but instead a path search specification). Any existing files will be loaded in sequence,
appending any content to the list of MIME type handler directives.
“Mailcap” files consist of a set of newline separated entries. Comment lines start with a number sign
‘#’ (in the first column!) and are ignored. Empty lines are also ignored. All other lines form
individual entries that must adhere to the syntax described below. To extend a single entry (not
comment) its line can be continued on follow lines if newline characters are “escaped” by preceding them
with the reverse solidus character ‘\’. The standard does not specify how leading whitespace of follow
lines is to be treated, therefore S-nail retains it.
“Mailcap” entries consist of a number of semicolon ‘;’ separated fields, and the reverse solidus ‘\’
character can be used to escape any following character including semicolon and itself. The first two
fields are mandatory and must occur in the specified order, the remaining fields are optional and may
appear in any order. Leading and trailing whitespace of content is ignored (removed).
The first field defines the MIME ‘TYPE/SUBTYPE’ the entry is about to handle (case-insensitively, and no
reverse solidus escaping is possible in this field). If the subtype is specified as an asterisk ‘*’ the
entry is meant to match all subtypes of the named type, e.g., ‘audio/*’ would match any audio type. The
second field defines the shell command which shall be used to “display” MIME parts of the given type; it
is implicitly called the view command.
For data “consuming” shell commands message (MIME part) data is passed via standard input unless the
given shell command includes one or more instances of the (unquoted) string ‘%s’, in which case these
instances will be replaced with a temporary filename and the data will have been stored in the file that
is being pointed to. Likewise, for data “producing” shell commands data is assumed to be generated on
standard output unless the given command includes (one ore multiple) ‘%s’. In any case any given ‘%s’
format is replaced with a(n already) properly quoted filename. Note that when a command makes use of a
temporary file via ‘%s’ then S-nail will remove it again, as if the x-mailx-tmpfile, x-mailx-tmpfile-fill
and x-mailx-tmpfile-unlink flags had been set; see below for more.
The optional fields either define a shell command or an attribute (flag) value, the latter being a single
word and the former being a keyword naming the field followed by an equals sign ‘=’ succeeded by a shell
command, and as usual for any “Mailcap” content any whitespace surrounding the equals sign will be
removed, too. Optional fields include the following:
compose A program that can be used to compose a new body or body part in the given format. (Currently
unused.)
composetyped
Similar to the compose field, but is to be used when the composing program needs to specify the
‘Content-type:’ header field to be applied to the composed data. (Currently unused.)
edit A program that can be used to edit a body or body part in the given format. (Currently
unused.)
print A program that can be used to print a message or body part in the given format. (Currently
unused.)
test Specifies a program to be run to test some condition, e.g., the machine architecture, or the
window system in use, to determine whether or not this mailcap entry applies. If the test
fails, a subsequent mailcap entry should be sought; also see x-mailx-test-once.
needsterminal
This flag field indicates that the given shell command must be run on an interactive terminal.
S-nail will temporarily release the terminal to the given command in interactive mode, in non-
interactive mode this entry will be entirely ignored; this flag implies x-mailx-noquote.
copiousoutput
A flag field which indicates that the output of the view command will be an extended stream of
textual output that can be (re)integrated into S-nail's normal visual display. It is mutually
exclusive with needsterminal.
textualnewlines
A flag field which indicates that this type of data is line-oriented and that, if encoded in
‘base64’, all newlines should be converted to canonical form (CRLF) before encoding, and will
be in that form after decoding. (Currently unused.)
nametemplate
This field gives a filename format, in which ‘%s’ will be replaced by a random string, the
joined combination of which will be used as the filename denoted by MAILX_FILENAME_TEMPORARY.
One could specify that a GIF file being passed to an image viewer should have a name ending in
‘.gif’ by using ‘nametemplate=%s.gif’. Note that S-nail ignores the name template unless that
solely specifies a filename suffix that consists of (ASCII) alphabetic and numeric characters,
the underscore and dot only.
x11-bitmap
Names a file, in X11 bitmap (xbm) format, which points to an appropriate icon to be used to
visually denote the presence of this kind of data. This field is not used by S-nail.
description
A textual description that describes this type of data.
x-mailx-even-if-not-interactive
An extension flag test field — by default handlers without copiousoutput are entirely ignored
in non-interactive mode, but if this flag is set then their use will be considered. It is an
error if this flag is set for commands that use the flag needsterminal.
x-mailx-noquote
An extension flag field that indicates that even a copiousoutput view command shall not be used
to generate message quotes (as it would be by default).
x-mailx-async
Extension flag field that denotes that the given view command shall be executed asynchronously,
without blocking S-nail. Cannot be used in conjunction with needsterminal; the standard output
of the command will go to /dev/null.
x-mailx-test-once
Extension flag which denotes whether the given test command shall be evaluated once only and
the (boolean) result be cached. This is handy if some global unchanging condition is to be
queried, like “running under the X Window System”.
x-mailx-tmpfile
Extension flag field that requests creation of a zero-sized temporary file, the name of which
is to be placed in the environment variable MAILX_FILENAME_TEMPORARY. It is an error to use
this flag with commands that include a ‘%s’ format.
x-mailx-tmpfile-fill
Normally the MIME part content is passed to the handler via standard input; if this flag is set
then the data will instead be written into the implied x-mailx-tmpfile. In order to cause
deletion of the temporary file you will have to set x-mailx-tmpfile-unlink explicitly! It is
an error to use this flag with commands that include a ‘%s’ format.
x-mailx-tmpfile-unlink
Extension flag field that requests that the temporary file shall be deleted automatically when
the command loop is entered again at latest. (Do not use this for asynchronous handlers.) It
is an error to use this flag with commands that include a ‘%s’ format, or in conjunction with
x-mailx-async, or without also setting x-mailx-tmpfile or x-mailx-tmpfile-fill.
x-mailx-tmpfile-keep
Using the string ‘%s’ implies the three tmpfile related flags above, but if you want, e.g.,
x-mailx-async and deal with the temporary file yourself, you can add in this flag to forcefully
ignore x-mailx-tmpfile-unlink.
The standard includes the possibility to define any number of additional entry fields, prefixed by ‘x-’.
Flag fields apply to the entire “Mailcap” entry — in some unusual cases, this may not be desirable, but
differentiation can be accomplished via separate entries, taking advantage of the fact that subsequent
entries are searched if an earlier one does not provide enough information. E.g., if a view command
needs to specify the needsterminal flag, but the compose command shall not, the following will help out
the latter (with enabled debug or an increased verbose level S-nail will show information about handler
evaluation):
application/postscript; ps-to-terminal %s; needsterminal
application/postscript; ps-to-terminal %s; compose=idraw %s
In fields any occurrence of the format string ‘%t’ will be replaced by the ‘TYPE/SUBTYPE’ specification.
Named parameters from the ‘Content-type:’ field may be placed in the command execution line using ‘%{’
followed by the parameter name and a closing ‘}’ character. The entire parameter should appear as a
single command line argument, regardless of embedded spaces; thus:
# Message
Content-type: multipart/mixed; boundary=42
# Mailcap file
multipart/*; /usr/local/bin/showmulti \
%t %{boundary} ; composetyped = /usr/local/bin/makemulti
# Executed shell command
/usr/local/bin/showmulti multipart/mixed 42
Note that S-nail does not support handlers for multipart MIME parts as shown in this example (as of
today). S-nail does not support the additional formats ‘%n’ and ‘%F’. An example file, also showing how
to properly deal with the expansion of ‘%s’, which includes any quotes that are necessary to make it a
valid shell argument by itself and thus will cause undesired behaviour when placed in additional user-
provided quotes:
# Comment line
text/richtext; richtext %s; copiousoutput
text/x-perl; perl -cWT %s
application/pdf; \
infile=%s\; \
trap "rm -f ${infile}" EXIT\; \
trap "exit 75" INT QUIT TERM\; \
mupdf %s; \
x-mailx-async; x-mailx-tmpfile-keep
application/*; echo "This is \"%t\" but \
is 50 \% Greek to me" \; < %s head -c 1024 | cat -vet; \
copiousoutput; x-mailx-noquote
Further reading: “HTML mail and MIME attachments”, “The mime.types files”, mimetype, MAILCAPS,
mime-counter-evidence, pipe-TYPE/SUBTYPE, pipe-EXTENSION.
The .netrc file
The .netrc file contains user credentials for machine accounts. The default location ~/.netrc may be
overridden by the NETRC environment variable. It is possible to load encrypted .netrc files by using an
appropriate value in netrc-pipe.
The file consists of space, tabulator or newline separated tokens. S-nail implements a parser that
supports a superset of the original BSD syntax, but users should nonetheless be aware of portability
glitches of that file format, shall their .netrc be usable across multiple programs and platforms:
• BSD does not support single, but only double quotation marks, e.g., ‘password="pass with spaces"’.
• BSD (only?) supports escaping of single characters via a reverse solidus (e.g., a space can be
escaped via ‘\ ’), in- as well as outside of a quoted string.
• BSD does not require a final quotation mark of the last user input token.
• The original BSD (Berknet) parser also supported a format which allowed tokens to be separated with
commas – whereas at least Hewlett-Packard still seems to support this syntax, S-nail does not!
• As a non-portable extension some widely-used programs support shell-style comments: if an input line
starts, after any amount of whitespace, with a number sign ‘#’, then the rest of the line is ignored.
• Whereas other programs may require that the .netrc file is accessible by only the user if it contains
a password token for any other login than “anonymous”, S-nail will always require these strict
permissions.
Of the following list of supported tokens S-nail only uses (and caches) machine, login and password. At
runtime the command netrc can be used to control S-nail's .netrc cache.
machine name
The hostname of the entries' machine, lowercase-normalized by S-nail before use. Any further
file content, until either end-of-file or the occurrence of another machine or a default first-
class token is bound (only related) to the machine name.
As an extension that should not be the cause of any worries S-nail supports a single wildcard
prefix for name:
machine *.example.com login USER password PASS
machine pop3.example.com login USER password PASS
machine smtp.example.com login USER password PASS
which would match ‘xy.example.com’ as well as ‘pop3.example.com’, but neither ‘example.com’ nor
‘local.smtp.example.com’. Note that in the example neither ‘pop3.example.com’ nor
‘smtp.example.com’ will be matched by the wildcard, since the exact matches take precedence (it
is however faster to specify it the other way around).
default This is the same as machine except that it is a fallback entry that is used shall none of the
specified machines match; only one default token may be specified, and it must be the last
first-class token.
login name
The user name on the remote machine.
password string
The user's password on the remote machine.
account string
Supply an additional account password. This is merely for FTP purposes.
macdef name
Define a macro. A macro is defined with the specified name; it is formed from all lines
beginning with the next line and continuing until a blank line is (consecutive newline
characters are) encountered. (Note that macdef entries cannot be utilized by multiple
machines, too, but must be defined following the machine they are intended to be used with.)
If a macro named init exists, it is automatically run as the last step of the login process.
This is merely for FTP purposes.
EXAMPLES
An example configuration
# This example assumes v15.0 compatibility mode
set v15-compat
# Request strict TLL transport layer security checks
set tls-verify=strict
# Where are the up-to-date TLS certificates?
# (Since we manage up-to-date ones explicitly, do not use any,
# possibly outdated, default certificates shipped with OpenSSL)
#set tls-ca-dir=/etc/ssl/certs
set tls-ca-file=/etc/ssl/certs/ca-certificates.crt
set tls-ca-no-defaults
#set tls-ca-flags=partial-chain
wysh set smime-ca-file="${tls-ca-file}" \
smime-ca-no-defaults #smime-ca-flags="${tls-ca-flags}"
# This could be outsourced to a central configuration file via
# tls-config-file plus tls-config-module if the used library allows.
# CipherString: explicitly define the list of ciphers, which may
# improve security, especially with protocols older than TLS v1.2.
# See ciphers(1). Possibly best to only use tls-config-pairs-HOST
# (or -USER@HOST), as necessary, again..
# Note that TLSv1.3 uses Ciphersuites= instead, which will join
# with CipherString (if protocols older than v1.3 are allowed)
# Curves: especially with TLSv1.3 curves selection may be desired.
# MinProtocol,MaxProtocol: do not use protocols older than TLS v1.2.
# Change this only when the remote server does not support it:
# maybe use chain support via tls-config-pairs-HOST / -USER@HOST
# to define such explicit exceptions, then, e.g.,
# MinProtocol=TLSv1.1
if [ "$tls-features" =% +ctx-set-maxmin-proto ]
wysh set tls-config-pairs='\
CipherString=TLSv1.2:!aNULL:!eNULL:@STRENGTH,\
Curves=P-521:P-384:P-256,\
MinProtocol=TLSv1.1'
else
wysh set tls-config-pairs='\
CipherString=TLSv1.2:!aNULL:!eNULL:@STRENGTH,\
Curves=P-521:P-384:P-256,\
Protocol=-ALL\,+TLSv1.1 \, +TLSv1.2\, +TLSv1.3'
endif
# Essential setting: select allowed character sets
set sendcharsets=utf-8,iso-8859-1
# A very kind option: when replying to a message, first try to
# use the same encoding that the original poster used herself!
set reply-in-same-charset
# When replying, do not merge From: and To: of the original message
# into To:. Instead old From: -> new To:, old To: -> merge Cc:.
set recipients-in-cc
# When sending messages, wait until the Mail-Transfer-Agent finishs.
# Only like this you will be able to see errors reported through the
# exit status of the MTA (including the built-in SMTP one)!
set sendwait
# Only use built-in MIME types, no mime.types(5) files
set mimetypes-load-control
# Default directory where we act in (relative to $HOME)
set folder=mail
# A leading "+" (often) means: under *folder*
# *record* is used to save copies of sent messages
set MBOX=+mbox.mbox DEAD=+dead.txt \
record=+sent.mbox record-files record-resent
# Make "file mymbox" and "file myrec" go to..
shortcut mymbox %:+mbox.mbox myrec +sent.mbox
# Not really optional, e.g., for S/MIME
set from='Your Name <address@exam.ple>'
# It may be necessary to set hostname and/or smtp-hostname
# if the "SERVER" of mta and "domain" of from do not match.
# The `urlencode' command can be used to encode USER and PASS
set mta=(smtps?|submissions?)://[USER[:PASS]@]SERVER[:PORT] \
smtp-auth=login/plain... \
smtp-use-starttls
# Never refuse to start into interactive mode, and more
set emptystart \
colour-pager crt= \
followup-to followup-to-honour=ask-yes fullnames \
history-file=+.s-nailhist history-size=-1 history-gabby \
mime-counter-evidence=0b1111 \
prompt='?\$?!\$!/\$^ERRNAME[\$account#\$mailbox-display]? ' \
reply-to-honour=ask-yes \
umask=
# Only include the selected header fields when typing messages
headerpick type retain from_ date from to cc subject \
message-id mail-followup-to reply-to
# ...when forwarding messages
headerpick forward retain subject date from to cc
# ...when saving message, etc.
#headerpick save ignore ^Original-.*$ ^X-.*$
# Some mailing lists
mlist '@xyz-editor\.xyz$' '@xyzf\.xyz$'
mlsubscribe '^xfans@xfans\.xyz$'
# Handle a few file extensions (to store MBOX databases)
filetype bz2 'bzip2 -dc' 'bzip2 -zc' \
gz 'gzip -dc' 'gzip -c' xz 'xz -dc' 'xz -zc' \
zst 'zstd -dc' 'zstd -19 -zc' \
zst.pgp 'gpg -d | zstd -dc' 'zstd -19 -zc | gpg -e'
# A real life example of a very huge free mail provider
# Instead of directly placing content inside `account',
# we `define' a macro: like that we can switch "accounts"
# from within *on-compose-splice*, for example!
define XooglX {
set folder=~/spool/XooglX inbox=+syste.mbox sent=+sent
set from='Your Name <address@examp.ple>'
set pop3-no-apop-pop.gmXil.com
shortcut pop %:pop3s://pop.gmXil.com
shortcut imap %:imaps://imap.gmXil.com
# Or, entirely IMAP based setup
#set folder=imaps://imap.gmail.com record="+[Gmail]/Sent Mail" \
# imap-cache=~/spool/cache
set mta=smtp://USER:PASS@smtp.gmXil.com smtp-use-starttls
# Alternatively:
set mta=smtps://USER:PASS@smtp.gmail.com:465
}
account XooglX {
\call XooglX
}
# Here is a pretty large one which does not allow sending mails
# if there is a domain name mismatch on the SMTP protocol level,
# which would bite us if the value of from does not match, e.g.,
# for people who have a sXXXXeforge project and want to speak
# with the mailing list under their project account (in from),
# still sending the message through their normal mail provider
define XandeX {
set folder=~/spool/XandeX inbox=+syste.mbox sent=+sent
set from='Your Name <address@exam.ple>'
shortcut pop %:pop3s://pop.yaXXex.com
shortcut imap %:imaps://imap.yaXXex.com
set mta=smtps://USER:PASS@smtp.yaXXex.com:465 \
hostname=yaXXex.com smtp-hostname=
}
account XandeX {
\call Xandex
}
# Create some new commands so that, e.g., `ls /tmp' will..
commandalias lls '!ls ${LS_COLOUR_FLAG} -aFlrS'
commandalias llS '!ls ${LS_COLOUR_FLAG} -aFlS'
set pipe-message/external-body='?* echo $MAILX_EXTERNAL_BODY_URL'
# We do not support gpg(1) directly yet. But simple --clearsign'd
# message parts can be dealt with as follows:
define V {
localopts yes
wysh set pipe-text/plain=$'?*#++=?\
< "${MAILX_FILENAME_TEMPORARY}" awk \
-v TMPFILE="${MAILX_FILENAME_TEMPORARY}" \'\
BEGIN{done=0}\
/^-----BEGIN PGP SIGNED MESSAGE-----/,/^$/ {\
if(done++ != 0)\
next;\
print "--- GPG --verify ---";\
system("gpg --verify " TMPFILE " 2>&1");\
print "--- GPG --verify ---";\
print "";\
next;\
}\
/^-----BEGIN PGP SIGNATURE-----/,\
/^-----END PGP SIGNATURE-----/{\
next;\
}\
{print}\
\''
print
}
commandalias V '\'call V
When storing passwords in ~/.mailrc appropriate permissions should be set on this file with ‘$ chmod 0600
~/.mailrc’. If the [Option]al netrc-lookup is available user credentials can be stored in the central ~/
.netrc file instead; e.g., here is a different version of the example account that sets up SMTP and POP3:
define XandeX {
set folder=~/spool/XandeX inbox=+syste.mbox sent=+sent
set from='Your Name <address@exam.ple>'
set netrc-lookup
# Load an encrypted ~/.netrc by uncommenting the next line
#set netrc-pipe='gpg -qd ~/.netrc.pgp'
set mta=smtps://smtp.yXXXXx.ru:465 \
smtp-hostname= hostname=yXXXXx.com
set pop3-keepalive=240 pop3-no-apop-pop.yXXXXx.ru
commandalias xp fi pop3s://pop.yXXXXx.ru
}
account XandeX {
\call XandeX
}
and, in the ~/.netrc file:
machine *.yXXXXx.ru login USER password PASS
This configuration should now work just fine:
$ echo text | s-nail -dvv -AXandeX -s Subject user@exam.ple
S/MIME step by step
[Option] The first thing that is needed for “Signed and encrypted messages with S/MIME” is a personal
certificate, and a private key. The certificate contains public information, in particular a name and
email address(es), and the public key that can be used by others to encrypt messages for the certificate
holder (the owner of the private key), and to verify signed messages generated with that certificate('s
private key). Whereas the certificate is included in each signed message, the private key must be kept
secret. It is used to decrypt messages that were previously encrypted with the public key, and to sign
messages.
For personal use it is recommended to get a S/MIME certificate from one of the major CAs on the Internet.
Many CAs offer such certificates for free. Usually offered is a combined certificate and private key in
PKCS#12 format which S-nail does not accept directly. To convert it to PEM format, the following shell
command can be used; please read on for how to use these PEM files.
$ openssl pkcs12 -in cert.p12 -out certpem.pem -clcerts -nodes
$ # Alternatively
$ openssl pkcs12 -in cert.p12 -out cert.pem -clcerts -nokeys
$ openssl pkcs12 -in cert.p12 -out key.pem -nocerts -nodes
There is also https://www.CAcert.org which issues client and server certificates to members of their
community for free; their root certificate (https://www.cacert.org/certs/root.crt) is often not in the
default set of trusted CA root certificates, though, which means their root certificate has to be
downloaded separately, and needs to be part of the S/MIME certificate validation chain by including it in
smime-ca-dir or as a vivid member of the smime-ca-file. But let us take a step-by-step tour on how to
setup S/MIME with a certificate from CAcert.org despite this situation!
First of all you will have to become a member of the CAcert.org community, simply by registrating
yourself via the web interface. Once you are, create and verify all email addresses you want to be able
to create signed and encrypted messages for/with using the corresponding entries of the web interface.
Now ready to create S/MIME certificates, so let us create a new “client certificate”, ensure to include
all email addresses that should be covered by the certificate in the following web form, and also to use
your name as the “common name”.
Create a private key and a certificate request on your local computer (please see the manual pages of the
used commands for more in-depth knowledge on what the used arguments etc. do):
$ openssl req -nodes -newkey rsa:4096 -keyout key.pem -out creq.pem
Afterwards copy-and-paste the content of “creq.pem” into the certificate-request (CSR) field of the web
form on the CAcert.org website (you may need to unfold some “advanced options” to see the corresponding
text field). This last step will ensure that your private key (which never left your box) and the
certificate belong together (through the public key that will find its way into the certificate via the
certificate-request). You are now ready and can create your CAcert certified certificate. Download and
store or copy-and-paste it as “pub.crt”.
Yay. In order to use your new S/MIME setup a combined private key/public key (certificate) file has to
be created:
$ cat key.pem pub.crt > ME@HERE.com.paired
This is the file S-nail will work with. If you have created your private key with a passphrase then
S-nail will ask you for it whenever a message is signed or decrypted, unless this operation has been
automated as described in “Signed and encrypted messages with S/MIME”. Set the following variables to
henceforth use S/MIME (setting smime-ca-file is of interest for verification only):
? set smime-ca-file=ALL-TRUSTED-ROOT-CERTS-HERE \
smime-sign-cert=ME@HERE.com.paired \
smime-sign-digest=SHA512 \
smime-sign
Using CRLs with S/MIME or TLS
[Option] Certification authorities (CAs) issue certificate revocation lists (CRLs) on a regular basis.
These lists contain the serial numbers of certificates that have been declared invalid after they have
been issued. Such usually happens because the private key for the certificate has been compromised,
because the owner of the certificate has left the organization that is mentioned in the certificate, etc.
To seriously use S/MIME or TLS verification, an up-to-date CRL is required for each trusted CA. There is
otherwise no method to distinguish between valid and invalidated certificates. S-nail currently offers
no mechanism to fetch CRLs, nor to access them on the Internet, so they have to be retrieved by some
external mechanism.
S-nail accepts CRLs in PEM format only; CRLs in DER format must be converted, like, e.g.:
$ openssl crl -inform DER -in crl.der -out crl.pem
To tell S-nail about the CRLs, a directory that contains all CRL files (and no other files) must be
created. The smime-crl-dir or tls-crl-dir variables, respectively, must then be set to point to that
directory. After that, S-nail requires a CRL to be present for each CA that is used to verify a
certificate.
FAQ
In general it is a good idea to turn on debug (-d) and / or verbose (-v, twice) if something does not
work well. Very often a diagnostic message can be produced that leads to the problems' solution.
S-nail shortly hangs on startup
This can have two reasons, one is the necessity to wait for a file lock and cannot be helped, the other
being that S-nail calls the function uname(2) in order to query the nodename of the box (sometimes the
real one is needed instead of the one represented by the internal variable hostname). One may have
varying success by ensuring that the real hostname and ‘localhost’ have entries in /etc/hosts, or, more
generally, that the name service is properly setup – and does hostname(1) return the expected value?
Does this local hostname have a domain suffix? RFC 6762 standardized the link-local top-level domain
‘.local’, try again after adding an (additional) entry with this extension.
I cannot login to Google mail (via OAuth)
Since 2014 some free service providers classify programs as “less secure” unless they use a special
authentication method (OAuth 2.0) which was not standardized for non-HTTP protocol authentication token
query until August 2015 (RFC 7628).
Different to Kerberos / GSSAPI, which is developed since the mid of the 1980s, where a user can easily
create a local authentication ticket for her- and himself with the locally installed kinit(1) program,
that protocol has no such local part but instead requires a world-wide-web query to create or fetch a
token; since there is no local cache this query would have to be performed whenever S-nail is invoked (in
interactive sessions situation may differ).
S-nail does not support OAuth. Because of this it is necessary to declare S-nail a “less secure app” (on
the providers account web page) in order to read and send mail. However, it also seems possible to take
the following steps instead:
1. give the provider the number of a mobile phone,
2. enable “2-Step Verification”,
3. create an application specific password (16 characters), and
4. use that special password instead of the real Google account password in S-nail (for more on that
see the section “On URL syntax and credential lookup”).
But, how about XOAUTH2 / OAUTHBEARER?
Following up “I cannot login to Google mail (via OAuth)” one OAuth-based authentication method is
available: the OAuth 2.0 bearer token usage as standardized in RFC 6750, also known as XOAUTH2 and
OAUTHBEARER, allows fetching a temporary access token via the web that can locally be used as a password.
The protocol is simple and extendable, token updates or even password changes via a simple TLS secured
server login would be possible in theory, but today a web browser and an external support tool are
prerequisites for using this authentication method. The token times out and must be refreshed via the
web periodically; in Kerberos / GSSAPI the local programs kinit(1) and kdestroy(1) offer user local
control, the latter also while offline.
Before being able to use OAUTHBEARER, some hurdles must be taken. Using GMail as an example, an
application (a simple name) needs to be registered, for which credentials need to be created. This
configuration step generates a “client ID” and a “client secret”. These two strings need to be saved
locally in a secure way. For GMail these initial configuration steps can be performed via
https://developers.google.com/identity/protocols/OAuth2. Thereafter access tokens can be requested, the
program available for download do do this for a GMail account is https://github.com/google/gmail-
oauth2-tools/blob/master/python/oauth2.py:
$ python oauth2.py --user=EMAIL \
--client-id=THE-ID --client-secret=THE-SECRET \
--generate_oauth2_token
To authorize token, visit this url and follow the directions:
https://accounts.google.com/o/oauth2/auth?client_id=...
Enter verification code: ...
Refresh Token: ...
Access Token: ...
Access Token Expiration Seconds: 3600
$ # The last three are the actual token responses.
$ # To refresh the granted token:
$ python oauth2.py --user=EMAIL \
--client-id=THE-ID --client-secret=THE-SECRET \
--refresh-token=THE-REFRESH-TOKEN
S-nail does not (yet) offer the possibility to (lazy) expand aka run shell commandos which are embedded
in variable content, or periodically run some command, therefore keeping an access token up-to-date from
within it can only be performed by setting the hook on-main-loop-tick, or (for sending only)
on-compose-splice. For more on authentication please see the section “On URL syntax and credential
lookup”.
Not "defunctional", but the editor key does not work
It can happen that the terminal library (see “On terminal control and line editor”, bind, termcap)
reports different codes than the terminal really sends, in which case S-nail will tell that a key binding
is functional, but will not be able to recognize it because the received data does not match anything
expected. Especially without the [Option]al terminal capability library support one reason for this may
be that the (possibly even non-existing) keypad is not turned on and the resulting layout reports the
keypad control codes for the normal keyboard keys. The verbose listing of bindings will show the byte
sequences that are expected.
To overcome the situation, use, e.g., the program cat(1), in conjunction with the command line option -v,
if available, to see the byte sequences which are actually produced by keypresses, and use the variable
termcap to make S-nail aware of them. E.g., the terminal this is typed on produces some false sequences,
here an example showing the shifted home key:
? set verbose
? bind*
# 1B 5B=[ 31=1 3B=; 32=2 48=H
bind base :kHOM z0
? x
$ cat -v
^[[H
$ s-nail -v -Stermcap='kHOM=\E[H'
? bind*
# 1B 5B=[ 48=H
bind base :kHOM z0
Can S-nail git-send-email?
Yes. Put (at least parts of) the following in your ~/.gitconfig:
[sendemail]
smtpserver = /usr/bin/s-nail
smtpserveroption = -t
#smtpserveroption = -Sexpandaddr
smtpserveroption = -Athe-account-you-need
##
suppresscc = all
suppressfrom = false
assume8bitEncoding = UTF-8
#to = /tmp/OUT
confirm = always
chainreplyto = true
multiedit = false
thread = true
quiet = true
annotate = true
Patches can also be send directly, for example:
$ git mail-patch HEAD^ |
s-nail -Athe-account-you-need -t RECEIVER
Howto handle stale dotlock files
file sometimes fails to open MBOX mail databases because creation of “dotlock files” is impossible due to
existing but unowned lock files. S-nail does not offer an option to deal with those files, because it is
considered a site policy what counts as unowned, and what not. The site policy is usually defined by
administrator(s), and expressed in the configuration of a locally installed MTA (for example Postfix
‘stale_lock_time=500s’). Therefore the suggestion:
$ </dev/null s-nail -s 'MTA: be no frog, handle lock' $LOGNAME
By sending a mail to yourself the local MTA can use its normal queue mechanism to try the delivery
multiple times, finally decide a lock file has become stale, and remove it.
IMAP CLIENT
[Option]ally there is IMAP client support available. This part of the program is obsolete and will
vanish in v15 with the large MIME and I/O layer rewrite, because it uses old-style blocking I/O and makes
excessive use of signal based long code jumps. Support can hopefully be readded later based on a new-
style I/O, with SysV signal handling. In fact the IMAP support had already been removed from the
codebase, but was reinstantiated on user demand: in effect the IMAP code is at the level of S-nail
v14.8.16 (with imapcodec being the sole exception), and should be treated with some care.
IMAP uses the ‘imap://’ and ‘imaps://’ protocol prefixes, and an IMAP-based folder may be used. IMAP
URLs (paths) undergo inspections and possible transformations before use (and the command imapcodec can
be used to manually apply them to any given argument). Hierarchy delimiters are normalized, a step which
is configurable via the imap-delim variable chain, but defaults to the first seen delimiter otherwise.
S-nail supports internationalised IMAP names, and en- and decodes the names from and to the ttycharset as
necessary and possible. If a mailbox name is expanded (see “Filename transformations”) to an IMAP
mailbox, all names that begin with `+' then refer to IMAP mailboxes below the folder target box, while
folder names prefixed by `@' refer to folders below the hierarchy base, e.g., the following lists all
folders below the current one when in an IMAP mailbox: ‘folders @’.
Note: some IMAP servers do not accept the creation of mailboxes in the hierarchy base, but require that
they are created as subfolders of `INBOX' – with such servers a folder name of the form
imaps://mylogin@imap.myisp.example/INBOX.
should be used (the last character is the server's hierarchy delimiter). The following IMAP-specific
commands exist:
cache Only applicable to cached IMAP mailboxes; takes a message list and reads the specified messages
into the IMAP cache.
connect If operating in disconnected mode on an IMAP mailbox, switch to online mode and connect to the
mail server while retaining the mailbox status. See the description of the disconnected
variable for more information.
disconnect
If operating in online mode on an IMAP mailbox, switch to disconnected mode while retaining the
mailbox status. See the description of the disconnected variable for more. A list of messages
may optionally be given as argument; the respective messages are then read into the cache
before the connection is closed, thus ‘disco *’ makes the entire mailbox available for
disconnected use.
imap Sends command strings directly to the current IMAP server. S-nail operates always in IMAP
`selected state' on the current mailbox; commands that change this will produce undesirable
results and should be avoided. Useful IMAP commands are:
create Takes the name of an IMAP mailbox as an argument and creates it.
getquotaroot (RFC 2087) Takes the name of an IMAP mailbox as an argument and prints the
quotas that apply to the mailbox. Not all IMAP servers support this
command.
namespace (RFC 2342) Takes no arguments and prints the Personal Namespaces, the
Other User's Namespaces and the Shared Namespaces. Each namespace type is
printed in parentheses; if there are multiple namespaces of the same type,
inner parentheses separate them. For each namespace a prefix and a
hierarchy separator is listed. Not all IMAP servers support this command.
imapcodec
Perform IMAP path transformations. Supports vput (see “Command modifiers”), and manages the
error number !. The first argument specifies the operation: e[ncode] normalizes hierarchy
delimiters (see imap-delim) and converts the strings from the locale ttycharset to the
internationalized variant used by IMAP, d[ecode] performs the reverse operation. Encoding will
honour the (global) value of imap-delim.
The following IMAP-specific internal variables exist:
disconnected
(Boolean) When an IMAP mailbox is selected and this variable is set, no connection to the
server is initiated. Instead, data is obtained from the local cache (see imap-cache).
Mailboxes that are not present in the cache and messages that have not yet entirely been
fetched from the server are not available; to fetch all messages in a mailbox at once, the
command `copy * /dev/null' can be used while still in connected mode. Changes that are made to
IMAP mailboxes in disconnected mode are queued and committed later when a connection to that
server is made. This procedure is not completely reliable since it cannot be guaranteed that
the IMAP unique identifiers (UIDs) on the server still match the ones in the cache at that
time. Data is saved to DEAD when this problem occurs.
disconnected-USER@HOST
The specified account is handled as described for the disconnected variable above, but other
accounts are not affected.
imap-auth-USER@HOST, imap-auth
Sets the IMAP authentication method. Supported are the default ‘login’, [v15-compat]
‘oauthbearer’ (see “FAQ” entry “But, how about XOAUTH2 / OAUTHBEARER?”), [v15-compat]
‘external’ and ‘externanon’ (for TLS secured connections which pass a client certificate via
tls-config-pairs), as well as the [Option]al ‘cram-md5’ and ‘gssapi’. All methods need a user
and a password except ‘gssapi’ and ‘external’, which only need the former. ‘externanon’ solely
builds upon the credentials passed via a client certificate, and is usually the way to go since
tested servers do not actually follow RFC 4422, and fail if additional credentials are actually
passed.
imap-cache
Enables caching of IMAP mailboxes. The value of this variable must point to a directory that
is either existent or can be created by S-nail. All contents of the cache can be deleted by
S-nail at any time; it is not safe to make assumptions about them.
imap-delim-USER@HOST, imap-delim-HOST, imap-delim
The hierarchy separator used by the IMAP server. Whenever an IMAP path is specified it will
undergo normalization. One of the normalization steps is the squeezing and adjustment of
hierarchy separators. If this variable is set, any occurrence of any character of the given
value that exists in the path will be replaced by the first member of the value; an empty value
will cause the default to be used, it is ‘/.’. If not set, we will reuse the first hierarchy
separator character that is discovered in a user-given mailbox name.
imap-keepalive-USER@HOST, imap-keepalive-HOST, imap-keepalive
IMAP servers may close the connection after a period of inactivity; the standard requires this
to be at least 30 minutes, but practical experience may vary. Setting this variable to a
numeric `value' greater than 0 causes a `NOOP' command to be sent each `value' seconds if no
other operation is performed.
imap-list-depth
When retrieving the list of folders on an IMAP server, the folders command stops after it has
reached a certain depth to avoid possible infinite loops. The value of this variable sets the
maximum depth allowed. The default is 2. If the folder separator on the current IMAP server
is a slash `/', this variable has no effect and the folders command does not descend to
subfolders.
imap-use-starttls-USER@HOST, imap-use-starttls-HOST, imap-use-starttls
Causes S-nail to issue a `STARTTLS' command to make an unencrypted IMAP session TLS encrypted.
This functionality is not supported by all servers, and is not used if the session is already
encrypted by the IMAPS method.
SEE ALSO
bogofilter(1), gpg(1), more(1), newaliases(1), openssl(1), sendmail(1), sh(1), spamassassin(1), iconv(3),
setlocale(3), aliases(5), termcap(5), terminfo(5), locale(7), mailaddr(7), re_format(7) (or regex(7)),
mailwrapper(8), sendmail(8)
HISTORY
M. Douglas McIlroy writes in his article “A Research UNIX Reader: Annotated Excerpts from the
Programmer's Manual, 1971-1986” that a mail(1) command already appeared in First Edition Unix in 1971:
Electronic mail was there from the start. Never satisfied with its exact behavior, everybody
touched it at one time or another: to assure the safety of simultaneous access, to improve privacy,
to survive crashes, to exploit uucp, to screen out foreign freeloaders, or whatever. Not until v7
did the interface change (Thompson). Later, as mail became global in its reach, Dave Presotto took
charge and brought order to communications with a grab-bag of external networks (v8).
BSD Mail, in large parts compatible with Unix mail, was written in 1978 by Kurt Shoens and developed as
part of the BSD Unix distribution until 1995. The common Unix and BSD denominator became standardized as
mailx(1) in the X/Open Portability Guide Issue 2 (January 1987). After the rise of Open Source BSD
variants Mail saw continuous development in the individual code forks, noticeably by Christos Zoulas in
NetBSD. Based upon this Nail, later Heirloom Mailx, was developed by Gunnar Ritter in the years 2000
until 2008. Since 2012 S-nail is maintained by Steffen Nurpmeso. This man page is derived from “The
Mail Reference Manual” that was originally written by Kurt Shoens.
Electronic mail exchange in general is a concept even older. The earliest well documented electronic
mail system was part of the Compatible Time Sharing System (CTSS) at MIT, its MAIL command had been
proposed in a staff planning memo at the end of 1964 and was implemented in mid-1965 when Tom Van Vleck
and Noel Morris wrote the necessary code. Similar communication programs were built for other
timesharing systems. One of the most ambitious and influential was Murray Turoff's EMISARI. Created in
1971 for the United States Office of Emergency Preparedness, EMISARI combined private electronic messages
with a chat system, public postings, voting, and a user directory.
During the 1960s it was common to connect a large number of terminals to a single, central computer.
Connecting two computers together was relatively unusual. This began to change with the development of
the ARPANET, the ancestor of today's Internet. In 1971 Ray Tomlinson adapted the SNDMSG program,
originally developed for the University of California at Berkeley timesharing system, to give it the
ability to transmit a message across the network into the mailbox of a user on a different computer. For
the first time it was necessary to specify the recipient's computer as well as an account name.
Tomlinson decided that the underused commercial at ‘@’ would work to separate the two.
Sending a message across the network was originally treated as a special instance of transmitting a file,
and so a MAIL command was included in RFC 385 on file transfer in 1972. Because it was not always clear
when or where a message had come from, RFC 561 in 1973 aimed to formalize electronic mail headers,
including “from”, “date”, and “subject”. In 1975 RFC 680 described fields to help with the transmission
of messages to multiple users, including “to”, “cc”, and “bcc”. In 1977 these features and others went
from best practices to a binding standard in RFC 733. Queen Elizabeth II of England became the first
head of state to send electronic mail on March 26 1976 while ceremonially opening a building in the
British Royal Signals and Radar Establishment (RSRE) in Malvern.
AUTHORS
Kurt Shoens, Edward Wang, Keith Bostic, Christos Zoulas, Gunnar Ritter. S-nail is developed by Steffen
Nurpmeso <s-mailx@lists.sdaoden.eu>.
CAVEATS
[v15 behaviour may differ] Interrupting an operation via SIGINT aka ‘control-C’ from anywhere else but a
command prompt is very problematic and likely to leave the program in an undefined state: many library
functions cannot deal with the siglongjmp(3) that this software (still) performs; even though efforts
have been taken to address this, no sooner but in v15 it will have been worked out: interruptions have
not been disabled in order to allow forceful breakage of hanging network connections, for example (all
this is unrelated to ignore).
The SMTP and POP3 protocol support of S-nail is very basic. Also, if it fails to contact its upstream
SMTP server, it will not make further attempts to transfer the message at a later time (setting save and
sendwait may be useful). If this is a concern, it might be better to set up a local SMTP server that is
capable of message queuing.
BUGS
When a network-based mailbox is open, directly changing to another network-based mailbox of a different
protocol (i.e., from POP3 to IMAP or vice versa) will cause a “deadlock”.
After deleting some message of a POP3 mailbox the header summary falsely claims that there are no
messages to display, one needs to perform a scroll or dot movement to restore proper state.
In ‘thread’ed sort mode a power user may encounter crashes very occasionally (this is may and very).
Please report bugs to the contact-mail address, e.g., from within s-nail: ‘? eval mail $contact-mail’.
Including the verbose output of the command version may be helpful, e.g.,
? wysh set escape=! verbose; vput version xy; unset verbose;\
eval mail $contact-mail
Bug subject
!I xy
!.
Information on the web at ‘$ s-nail -X 'echo $contact-web; x'’.
Debian August 17, 2019 S-NAIL(1)