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NAME
ex — text editor
SYNOPSIS
ex [-rR] [-s|-v] [-c command] [-t tagstring] [-w size] [file...]
DESCRIPTION
The ex utility is a line-oriented text editor. There are two other modes of the editor—
open and visual—in which screen-oriented editing is available. This is described more
fully by the ex open and visual commands and in vi.
If an operand is '-', the results are unspecified.
This section uses the term edit buffer to describe the current working text. No specific
implementation is implied by this term. All editing changes are performed on the edit
buffer, and no changes to it shall affect any file until an editor command writes the
file.
Certain terminals do not have all the capabilities necessary to support the complete ex
definition, such as the full-screen editing commands (visual mode or open mode). When
these commands cannot be supported on such terminals, this condition shall not produce an
error message such as ``not an editor command'' or report a syntax error. The
implementation may either accept the commands and produce results on the screen that are
the result of an unsuccessful attempt to meet the requirements of this volume of
POSIX.1‐2017 or report an error describing the terminal-related deficiency.
OPTIONS
The ex utility shall conform to the Base Definitions volume of POSIX.1‐2017, Section 12.2,
Utility Syntax Guidelines, except for the unspecified usage of '-', and that '+' may be
recognized as an option delimiter as well as '-'.
The following options shall be supported:
-c command
Specify an initial command to be executed in the first edit buffer loaded from
an existing file (see the EXTENDED DESCRIPTION section). Implementations may
support more than a single -c option. In such implementations, the specified
commands shall be executed in the order specified on the command line.
-r Recover the named files (see the EXTENDED DESCRIPTION section). Recovery
information for a file shall be saved during an editor or system crash (for
example, when the editor is terminated by a signal which the editor can catch),
or after the use of an ex preserve command.
A crash in this context is an unexpected failure of the system or utility that
requires restarting the failed system or utility. A system crash implies that
any utilities running at the time also crash. In the case of an editor or system
crash, the number of changes to the edit buffer (since the most recent preserve
command) that will be recovered is unspecified.
If no file operands are given and the -t option is not specified, all other
options, the EXINIT variable, and any .exrc files shall be ignored; a list of
all recoverable files available to the invoking user shall be written, and the
editor shall exit normally without further action.
-R Set readonly edit option.
-s Prepare ex for batch use by taking the following actions:
* Suppress writing prompts and informational (but not diagnostic) messages.
* Ignore the value of TERM and any implementation default terminal type and
assume the terminal is a type incapable of supporting open or visual modes;
see the visual command and the description of vi.
* Suppress the use of the EXINIT environment variable and the reading of any
.exrc file; see the EXTENDED DESCRIPTION section.
* Suppress autoindentation, ignoring the value of the autoindent edit option.
-t tagstring
Edit the file containing the specified tagstring; see ctags. The tags feature
represented by -t tagstring and the tag command is optional. It shall be
provided on any system that also provides a conforming implementation of ctags;
otherwise, the use of -t produces undefined results. On any system, it shall be
an error to specify more than a single -t option.
-v Begin in visual mode (see vi).
-w size Set the value of the window editor option to size.
OPERANDS
The following operand shall be supported:
file A pathname of a file to be edited.
STDIN
The standard input consists of a series of commands and input text, as described in the
EXTENDED DESCRIPTION section. The implementation may limit each line of standard input to
a length of {LINE_MAX}.
If the standard input is not a terminal device, it shall be as if the -s option had been
specified.
If a read from the standard input returns an error, or if the editor detects an end-of-
file condition from the standard input, it shall be equivalent to a SIGHUP asynchronous
event.
INPUT FILES
Input files shall be text files or files that would be text files except for an incomplete
last line that is not longer than {LINE_MAX}-1 bytes in length and contains no NUL
characters. By default, any incomplete last line shall be treated as if it had a trailing
<newline>. The editing of other forms of files may optionally be allowed by ex
implementations.
The .exrc files and source files shall be text files consisting of ex commands; see the
EXTENDED DESCRIPTION section.
By default, the editor shall read lines from the files to be edited without interpreting
any of those lines as any form of editor command.
ENVIRONMENT VARIABLES
The following environment variables shall affect the execution of ex:
COLUMNS Override the system-selected horizontal screen size. See the Base Definitions
volume of POSIX.1‐2017, Chapter 8, Environment Variables for valid values and
results when it is unset or null.
EXINIT Determine a list of ex commands that are executed on editor start-up. See the
EXTENDED DESCRIPTION section for more details of the initialization phase.
HOME Determine a pathname of a directory that shall be searched for an editor start-
up file named .exrc; see the EXTENDED DESCRIPTION section.
LANG Provide a default value for the internationalization variables that are unset or
null. (See the Base Definitions volume of POSIX.1‐2017, Section 8.2,
Internationalization Variables for the precedence of internationalization
variables used to determine the values of locale categories.)
LC_ALL If set to a non-empty string value, override the values of all the other
internationalization variables.
LC_COLLATE
Determine the locale for the behavior of ranges, equivalence classes, and multi-
character collating elements within regular expressions.
LC_CTYPE Determine the locale for the interpretation of sequences of bytes of text data
as characters (for example, single-byte as opposed to multi-byte characters in
arguments and input files), the behavior of character classes within regular
expressions, the classification of characters as uppercase or lowercase letters,
the case conversion of letters, and the detection of word boundaries.
LC_MESSAGES
Determine the locale that should be used to affect the format and contents of
diagnostic messages written to standard error.
LINES Override the system-selected vertical screen size, used as the number of lines
in a screenful and the vertical screen size in visual mode. See the Base
Definitions volume of POSIX.1‐2017, Chapter 8, Environment Variables for valid
values and results when it is unset or null.
NLSPATH Determine the location of message catalogs for the processing of LC_MESSAGES.
PATH Determine the search path for the shell command specified in the ex editor
commands !, shell, read, and write, and the open and visual mode command !; see
the description of command search and execution in Section 2.9.1.1, Command
Search and Execution.
SHELL Determine the preferred command line interpreter for use as the default value of
the shell edit option.
TERM Determine the name of the terminal type. If this variable is unset or null, an
unspecified default terminal type shall be used.
ASYNCHRONOUS EVENTS
The following term is used in this and following sections to specify command and
asynchronous event actions:
complete write
A complete write is a write of the entire contents of the edit buffer to a file
of a type other than a terminal device, or the saving of the edit buffer caused
by the user executing the ex preserve command. Writing the contents of the edit
buffer to a temporary file that will be removed when the editor exits shall not
be considered a complete write.
The following actions shall be taken upon receipt of signals:
SIGINT If the standard input is not a terminal device, ex shall not write the file or
return to command or text input mode, and shall exit with a non-zero exit
status.
Otherwise, if executing an open or visual text input mode command, ex in receipt
of SIGINT shall behave identically to its receipt of the <ESC> character.
Otherwise:
1. If executing an ex text input mode command, all input lines that have been
completely entered shall be resolved into the edit buffer, and any partially
entered line shall be discarded.
2. If there is a currently executing command, it shall be aborted and a message
displayed. Unless otherwise specified by the ex or vi command descriptions,
it is unspecified whether any lines modified by the executing command appear
modified, or as they were before being modified by the executing command, in
the buffer.
If the currently executing command was a motion command, its associated
command shall be discarded.
3. If in open or visual command mode, the terminal shall be alerted.
4. The editor shall then return to command mode.
SIGCONT The screen shall be refreshed if in open or visual mode.
SIGHUP If the edit buffer has been modified since the last complete write, ex shall
attempt to save the edit buffer so that it can be recovered later using the -r
option or the ex recover command. The editor shall not write the file or return
to command or text input mode, and shall terminate with a non-zero exit status.
SIGTERM Refer to SIGHUP.
The action taken for all other signals is unspecified.
STDOUT
The standard output shall be used only for writing prompts to the user, for informational
messages, and for writing lines from the file.
STDERR
The standard error shall be used only for diagnostic messages.
OUTPUT FILES
The output from ex shall be text files.
EXTENDED DESCRIPTION
Only the ex mode of the editor is described in this section. See vi for additional editing
capabilities available in ex.
When an error occurs, ex shall write a message. If the terminal supports a standout mode
(such as inverse video), the message shall be written in standout mode. If the terminal
does not support a standout mode, and the edit option errorbells is set, an alert action
shall precede the error message.
By default, ex shall start in command mode, which shall be indicated by a : prompt; see
the prompt command. Text input mode can be entered by the append, insert, or change
commands; it can be exited (and command mode re-entered) by typing a <period> ('.') alone
at the beginning of a line.
Initialization in ex and vi
The following symbols are used in this and following sections to specify locations in the
edit buffer:
alternate and current pathnames
Two pathnames, named current and alternate, are maintained by the editor. Any ex
commands that take filenames as arguments shall set them as follows:
1. If a file argument is specified to the ex edit, ex, or recover commands, or if
an ex tag command replaces the contents of the edit buffer.
a. If the command replaces the contents of the edit buffer, the current
pathname shall be set to the file argument or the file indicated by the tag,
and the alternate pathname shall be set to the previous value of the current
pathname.
b. Otherwise, the alternate pathname shall be set to the file argument.
2. If a file argument is specified to the ex next command:
a. If the command replaces the contents of the edit buffer, the current
pathname shall be set to the first file argument, and the alternate pathname
shall be set to the previous value of the current pathname.
3. If a file argument is specified to the ex file command, the current pathname
shall be set to the file argument, and the alternate pathname shall be set to
the previous value of the current pathname.
4. If a file argument is specified to the ex read and write commands (that is, when
reading or writing a file, and not to the program named by the shell edit
option), or a file argument is specified to the ex xit command:
a. If the current pathname has no value, the current pathname shall be set to
the file argument.
b. Otherwise, the alternate pathname shall be set to the file argument.
If the alternate pathname is set to the previous value of the current pathname when
the current pathname had no previous value, then the alternate pathname shall have
no value as a result.
current line
The line of the edit buffer referenced by the cursor. Each command description
specifies the current line after the command has been executed, as the current line
value. When the edit buffer contains no lines, the current line shall be zero; see
Addressing in ex.
current column
The current display line column occupied by the cursor. (The columns shall be
numbered beginning at 1.) Each command description specifies the current column
after the command has been executed, as the current column value. This column is an
ideal column that is remembered over the lifetime of the editor. The actual display
line column upon which the cursor rests may be different from the current column;
see the cursor positioning discussion in Command Descriptions in vi.
set to non-<blank>
A description for a current column value, meaning that the current column shall be
set to the last display line column on which is displayed any part of the first
non-<blank> of the line. If the line has no non-<blank> non-<newline> characters,
the current column shall be set to the last display line column on which is
displayed any part of the last non-<newline> character in the line. If the line is
empty, the current column shall be set to column position 1.
The length of lines in the edit buffer may be limited to {LINE_MAX} bytes. In open and
visual mode, the length of lines in the edit buffer may be limited to the number of
characters that will fit in the display. If either limit is exceeded during editing, an
error message shall be written. If either limit is exceeded by a line read in from a file,
an error message shall be written and the edit session may be terminated.
If the editor stops running due to any reason other than a user command, and the edit
buffer has been modified since the last complete write, it shall be equivalent to a SIGHUP
asynchronous event. If the system crashes, it shall be equivalent to a SIGHUP asynchronous
event.
During initialization (before the first file is copied into the edit buffer or any user
commands from the terminal are processed) the following shall occur:
1. If the environment variable EXINIT is set, the editor shall execute the ex commands
contained in that variable.
2. If the EXINIT variable is not set, and all of the following are true:
a. The HOME environment variable is not null and not empty.
b. The file .exrc in the directory referred to by the HOME environment variable:
i. Exists
ii. Is owned by the same user ID as the real user ID of the process or the
process has appropriate privileges
iii. Is not writable by anyone other than the owner
the editor shall execute the ex commands contained in that file.
3. If and only if all of the following are true:
a. The current directory is not referred to by the HOME environment variable.
b. A command in the EXINIT environment variable or a command in the .exrc file in the
directory referred to by the HOME environment variable sets the editor option
exrc.
c. The .exrc file in the current directory:
i. Exists
ii. Is owned by the same user ID as the real user ID of the process, or by one of
a set of implementation-defined user IDs
iii. Is not writable by anyone other than the owner
the editor shall attempt to execute the ex commands contained in that file.
Lines in any .exrc file that are blank lines shall be ignored. If any .exrc file exists,
but is not read for ownership or permission reasons, it shall be an error.
After the EXINIT variable and any .exrc files are processed, the first file specified by
the user shall be edited, as follows:
1. If the user specified the -t option, the effect shall be as if the ex tag command was
entered with the specified argument, with the exception that if tag processing does
not result in a file to edit, the effect shall be as described in step 3. below.
2. Otherwise, if the user specified any command line file arguments, the effect shall be
as if the ex edit command was entered with the first of those arguments as its file
argument.
3. Otherwise, the effect shall be as if the ex edit command was entered with a
nonexistent filename as its file argument. It is unspecified whether this action shall
set the current pathname. In an implementation where this action does not set the
current pathname, any editor command using the current pathname shall fail until an
editor command sets the current pathname.
If the -r option was specified, the first time a file in the initial argument list or a
file specified by the -t option is edited, if recovery information has previously been
saved about it, that information shall be recovered and the editor shall behave as if the
contents of the edit buffer have already been modified. If there are multiple instances of
the file to be recovered, the one most recently saved shall be recovered, and an
informational message that there are previous versions of the file that can be recovered
shall be written. If no recovery information about a file is available, an informational
message to this effect shall be written, and the edit shall proceed as usual.
If the -c option was specified, the first time a file that already exists (including a
file that might not exist but for which recovery information is available, when the -r
option is specified) replaces or initializes the contents of the edit buffer, the current
line shall be set to the last line of the edit buffer, the current column shall be set to
non-<blank>, and the ex commands specified with the -c option shall be executed. In this
case, the current line and current column shall not be set as described for the command
associated with the replacement or initialization of the edit buffer contents. However, if
the -t option or a tag command is associated with this action, the -c option commands
shall be executed and then the movement to the tag shall be performed.
The current argument list shall initially be set to the filenames specified by the user on
the command line. If no filenames are specified by the user, the current argument list
shall be empty. If the -t option was specified, it is unspecified whether any filename
resulting from tag processing shall be prepended to the current argument list. In the case
where the filename is added as a prefix to the current argument list, the current argument
list reference shall be set to that filename. In the case where the filename is not added
as a prefix to the current argument list, the current argument list reference shall
logically be located before the first of the filenames specified on the command line (for
example, a subsequent ex next command shall edit the first filename from the command
line). If the -t option was not specified, the current argument list reference shall be to
the first of the filenames on the command line.
Addressing in ex
Addressing in ex relates to the current line and the current column; the address of a line
is its 1-based line number, the address of a column is its 1-based count from the
beginning of the line. Generally, the current line is the last line affected by a command.
The current line number is the address of the current line. In each command description,
the effect of the command on the current line number and the current column is described.
Addresses are constructed as follows:
1. The character '.' (period) shall address the current line.
2. The character '$' shall address the last line of the edit buffer.
3. The positive decimal number n shall address the nth line of the edit buffer.
4. The address "'x" refers to the line marked with the mark name character 'x', which
shall be a lowercase letter from the portable character set, the backquote character,
or the single-quote character. It shall be an error if the line that was marked is not
currently present in the edit buffer or the mark has not been set. Lines can be marked
with the ex mark or k commands, or the vi m command.
5. A regular expression enclosed by <slash> characters ('/') shall address the first line
found by searching forwards from the line following the current line toward the end of
the edit buffer and stopping at the first line for which the line excluding the
terminating <newline> matches the regular expression. As stated in Regular Expressions
in ex, an address consisting of a null regular expression delimited by <slash>
characters ("//") shall address the next line for which the line excluding the
terminating <newline> matches the last regular expression encountered. In addition,
the second <slash> can be omitted at the end of a command line. If the wrapscan edit
option is set, the search shall wrap around to the beginning of the edit buffer and
continue up to and including the current line, so that the entire edit buffer is
searched. Within the regular expression, the sequence "\/" shall represent a literal
<slash> instead of the regular expression delimiter.
6. A regular expression enclosed in <question-mark> characters ('?') shall address the
first line found by searching backwards from the line preceding the current line
toward the beginning of the edit buffer and stopping at the first line for which the
line excluding the terminating <newline> matches the regular expression. An address
consisting of a null regular expression delimited by <question-mark> characters ("??")
shall address the previous line for which the line excluding the terminating <newline>
matches the last regular expression encountered. In addition, the second <question-
mark> can be omitted at the end of a command line. If the wrapscan edit option is set,
the search shall wrap around from the beginning of the edit buffer to the end of the
edit buffer and continue up to and including the current line, so that the entire edit
buffer is searched. Within the regular expression, the sequence "\?" shall represent a
literal <question-mark> instead of the RE delimiter.
7. A <plus-sign> ('+') or a <hyphen-minus> ('-') followed by a decimal number shall
address the current line plus or minus the number. A '+' or '-' not followed by a
decimal number shall address the current line plus or minus 1.
Addresses can be followed by zero or more address offsets, optionally <blank>-separated.
Address offsets are constructed as follows:
1. A '+' or '-' immediately followed by a decimal number shall add (subtract) the
indicated number of lines to (from) the address. A '+' or '-' not followed by a
decimal number shall add (subtract) 1 to (from) the address.
2. A decimal number shall add the indicated number of lines to the address.
It shall not be an error for an intermediate address value to be less than zero or greater
than the last line in the edit buffer. It shall be an error for the final address value to
be less than zero or greater than the last line in the edit buffer.
Commands take zero, one, or two addresses; see the descriptions of 1addr and 2addr in
Command Descriptions in ex. If more than the required number of addresses are provided to
a command that requires zero addresses, it shall be an error. Otherwise, if more than the
required number of addresses are provided to a command, the addresses specified first
shall be evaluated and then discarded until the maximum number of valid addresses remain.
Addresses shall be separated from each other by a <comma> (',') or a <semicolon> (';').
If no address is specified before or after a <comma> or <semicolon> separator, it shall be
as if the address of the current line was specified before or after the separator. In the
case of a <semicolon> separator, the current line ('.') shall be set to the first
address, and only then will the next address be calculated. This feature can be used to
determine the starting line for forwards and backwards searches (see rules 5. and 6.).
A <percent-sign> ('%') shall be equivalent to entering the two addresses "1,$".
Any delimiting <blank> characters between addresses, address separators, or address
offsets shall be discarded.
Command Line Parsing in ex
The following symbol is used in this and following sections to describe parsing behavior:
escape If a character is referred to as ``<backslash>-escaped'' or ``<control>‐V-
escaped'', it shall mean that the character acquired or lost a special meaning
by virtue of being preceded, respectively, by a <backslash> or <control>‐V
character. Unless otherwise specified, the escaping character shall be discarded
at that time and shall not be further considered for any purpose.
Command-line parsing shall be done in the following steps. For each step, characters
already evaluated shall be ignored; that is, the phrase ``leading character'' refers to
the next character that has not yet been evaluated.
1. Leading <colon> characters shall be skipped.
2. Leading <blank> characters shall be skipped.
3. If the leading character is a double-quote character, the characters up to and
including the next non-<backslash>-escaped <newline> shall be discarded, and any
subsequent characters shall be parsed as a separate command.
4. Leading characters that can be interpreted as addresses shall be evaluated; see
Addressing in ex.
5. Leading <blank> characters shall be skipped.
6. If the next character is a <vertical-line> character or a <newline>:
a. If the next character is a <newline>:
i. If ex is in open or visual mode, the current line shall be set to the last
address specified, if any.
ii. Otherwise, if the last command was terminated by a <vertical-line> character,
no action shall be taken; for example, the command "||<newline>" shall
execute two implied commands, not three.
iii. Otherwise, step 6.b. shall apply.
b. Otherwise, the implied command shall be the print command. The last #, p, and l
flags specified to any ex command shall be remembered and shall apply to this
implied command. Executing the ex number, print, or list command shall set the
remembered flags to #, nothing, and l, respectively, plus any other flags
specified for that execution of the number, print, or list command.
If ex is not currently performing a global or v command, and no address or count
is specified, the current line shall be incremented by 1 before the command is
executed. If incrementing the current line would result in an address past the
last line in the edit buffer, the command shall fail, and the increment shall not
happen.
c. The <newline> or <vertical-line> character shall be discarded and any subsequent
characters shall be parsed as a separate command.
7. The command name shall be comprised of the next character (if the character is not
alphabetic), or the next character and any subsequent alphabetic characters (if the
character is alphabetic), with the following exceptions:
a. Commands that consist of any prefix of the characters in the command name delete,
followed immediately by any of the characters 'l', 'p', '+', '-', or '#' shall be
interpreted as a delete command, followed by a <blank>, followed by the characters
that were not part of the prefix of the delete command. The maximum number of
characters shall be matched to the command name delete; for example, "del" shall
not be treated as "de" followed by the flag l.
b. Commands that consist of the character 'k', followed by a character that can be
used as the name of a mark, shall be equivalent to the mark command followed by a
<blank>, followed by the character that followed the 'k'.
c. Commands that consist of the character 's', followed by characters that could be
interpreted as valid options to the s command, shall be the equivalent of the s
command, without any pattern or replacement values, followed by a <blank>,
followed by the characters after the 's'.
8. The command name shall be matched against the possible command names, and a command
name that contains a prefix matching the characters specified by the user shall be the
executed command. In the case of commands where the characters specified by the user
could be ambiguous, the executed command shall be as follows:
┌───┬────────┬┬───┬───────┬┬───┬───────┐
│a │ append ││n │ next ││t │ t │
│c │ change ││p │ print ││u │ undo │
│ch │ change ││pr │ print ││un │ undo │
│e │ edit ││r │ read ││v │ v │
│m │ move ││re │ read ││w │ write │
│ma │ mark ││s │ s ││ │ │
└───┴────────┴┴───┴───────┴┴───┴───────┘
Implementation extensions with names causing similar ambiguities shall not be checked
for a match until all possible matches for commands specified by POSIX.1‐2008 have
been checked.
9. If the command is a ! command, or if the command is a read command followed by zero
or more <blank> characters and a !, or if the command is a write command followed by
one or more <blank> characters and a !, the rest of the command shall include all
characters up to a non-<backslash>-escaped <newline>. The <newline> shall be
discarded and any subsequent characters shall be parsed as a separate ex command.
10. Otherwise, if the command is an edit, ex, or next command, or a visual command while
in open or visual mode, the next part of the command shall be parsed as follows:
a. Any '!' character immediately following the command shall be skipped and be part
of the command.
b. Any leading <blank> characters shall be skipped and be part of the command.
c. If the next character is a '+', characters up to the first non-<backslash>-escaped
<newline> or non-<backslash>-escaped <blank> shall be skipped and be part of the
command.
d. The rest of the command shall be determined by the steps specified in paragraph
12.
11. Otherwise, if the command is a global, open, s, or v command, the next part of the
command shall be parsed as follows:
a. Any leading <blank> characters shall be skipped and be part of the command.
b. If the next character is not an alphanumeric, double-quote, <newline>,
<backslash>, or <vertical-line> character:
i. The next character shall be used as a command delimiter.
ii. If the command is a global, open, or v command, characters up to the first
non-<backslash>-escaped <newline>, or first non-<backslash>-escaped delimiter
character, shall be skipped and be part of the command.
iii. If the command is an s command, characters up to the first
non-<backslash>-escaped <newline>, or second non-<backslash>-escaped
delimiter character, shall be skipped and be part of the command.
c. If the command is a global or v command, characters up to the first
non-<backslash>-escaped <newline> shall be skipped and be part of the command.
d. Otherwise, the rest of the command shall be determined by the steps specified in
paragraph 12.
12. Otherwise:
a. If the command was a map, unmap, abbreviate, or unabbreviate command, characters
up to the first non-<control>‐V-escaped <newline>, <vertical-line>, or double-
quote character shall be skipped and be part of the command.
b. Otherwise, characters up to the first non-<backslash>-escaped <newline>,
<vertical-line>, or double-quote character shall be skipped and be part of the
command.
c. If the command was an append, change, or insert command, and the step 12.b. ended
at a <vertical-line> character, any subsequent characters, up to the next
non-<backslash>-escaped <newline> shall be used as input text to the command.
d. If the command was ended by a double-quote character, all subsequent characters,
up to the next non-<backslash>-escaped <newline>, shall be discarded.
e. The terminating <newline> or <vertical-line> character shall be discarded and any
subsequent characters shall be parsed as a separate ex command.
Command arguments shall be parsed as described by the Synopsis and Description of each
individual ex command. This parsing shall not be <blank>-sensitive, except for the !
argument, which must follow the command name without intervening <blank> characters, and
where it would otherwise be ambiguous. For example, count and flag arguments need not be
<blank>-separated because "d22p" is not ambiguous, but file arguments to the ex next
command must be separated by one or more <blank> characters. Any <blank> in command
arguments for the abbreviate, unabbreviate, map, and unmap commands can be <control>‐V-
escaped, in which case the <blank> shall not be used as an argument delimiter. Any <blank>
in the command argument for any other command can be <backslash>-escaped, in which case
that <blank> shall not be used as an argument delimiter.
Within command arguments for the abbreviate, unabbreviate, map, and unmap commands, any
character can be <control>‐V-escaped. All such escaped characters shall be treated
literally and shall have no special meaning. Within command arguments for all other ex
commands that are not regular expressions or replacement strings, any character that would
otherwise have a special meaning can be <backslash>-escaped. Escaped characters shall be
treated literally, without special meaning as shell expansion characters or '!', '%', and
'#' expansion characters. See Regular Expressions in ex and Replacement Strings in ex for
descriptions of command arguments that are regular expressions or replacement strings.
Non-<backslash>-escaped '%' characters appearing in file arguments to any ex command shall
be replaced by the current pathname; unescaped '#' characters shall be replaced by the
alternate pathname. It shall be an error if '%' or '#' characters appear unescaped in an
argument and their corresponding values are not set.
Non-<backslash>-escaped '!' characters in the arguments to either the ex ! command or
the open and visual mode ! command, or in the arguments to the ex read command, where the
first non-<blank> after the command name is a '!' character, or in the arguments to the
ex write command where the command name is followed by one or more <blank> characters and
the first non-<blank> after the command name is a '!' character, shall be replaced with
the arguments to the last of those three commands as they appeared after all unescaped
'%', '#', and '!' characters were replaced. It shall be an error if '!' characters
appear unescaped in one of these commands and there has been no previous execution of one
of these commands.
If an error occurs during the parsing or execution of an ex command:
* An informational message to this effect shall be written. Execution of the ex command
shall stop, and the cursor (for example, the current line and column) shall not be
further modified.
* If the ex command resulted from a map expansion, all characters from that map
expansion shall be discarded, except as otherwise specified by the map command.
* Otherwise, if the ex command resulted from the processing of an EXINIT environment
variable, a .exrc file, a :source command, a -c option, or a +command specified to an
ex edit, ex, next, or visual command, no further commands from the source of the
commands shall be executed.
* Otherwise, if the ex command resulted from the execution of a buffer or a global or v
command, no further commands caused by the execution of the buffer or the global or v
command shall be executed.
* Otherwise, if the ex command was not terminated by a <newline>, all characters up to
and including the next non-<backslash>-escaped <newline> shall be discarded.
Input Editing in ex
The following symbol is used in this and the following sections to specify command
actions:
word In the POSIX locale, a word consists of a maximal sequence of letters, digits,
and underscores, delimited at both ends by characters other than letters,
digits, or underscores, or by the beginning or end of a line or the edit buffer.
When accepting input characters from the user, in either ex command mode or ex text input
mode, ex shall enable canonical mode input processing, as defined in the System Interfaces
volume of POSIX.1‐2017.
If in ex text input mode:
1. If the number edit option is set, ex shall prompt for input using the line number that
would be assigned to the line if it is entered, in the format specified for the ex
number command.
2. If the autoindent edit option is set, ex shall prompt for input using autoindent
characters, as described by the autoindent edit option. autoindent characters shall
follow the line number, if any.
If in ex command mode:
1. If the prompt edit option is set, input shall be prompted for using a single ':'
character; otherwise, there shall be no prompt.
The input characters in the following sections shall have the following effects on the
input line.
Scroll
Synopsis:
eof
See the description of the stty eof character in stty.
If in ex command mode:
If the eof character is the first character entered on the line, the line shall be
evaluated as if it contained two characters: a <control>‐D and a <newline>.
Otherwise, the eof character shall have no special meaning.
If in ex text input mode:
If the cursor follows an autoindent character, the autoindent characters in the
line shall be modified so that a part of the next text input character will be
displayed on the first column in the line after the previous shiftwidth edit option
column boundary, and the user shall be prompted again for input for the same line.
Otherwise, if the cursor follows a '0', which follows an autoindent character, and
the '0' was the previous text input character, the '0' and all autoindent
characters in the line shall be discarded, and the user shall be prompted again for
input for the same line.
Otherwise, if the cursor follows a '^', which follows an autoindent character, and
the '^' was the previous text input character, the '^' and all autoindent
characters in the line shall be discarded, and the user shall be prompted again for
input for the same line. In addition, the autoindent level for the next input line
shall be derived from the same line from which the autoindent level for the current
input line was derived.
Otherwise, if there are no autoindent or text input characters in the line, the eof
character shall be discarded.
Otherwise, the eof character shall have no special meaning.
<newline>
Synopsis:
<newline>
<control>-J
If in ex command mode:
Cause the command line to be parsed; <control>‐J shall be mapped to the <newline>
for this purpose.
If in ex text input mode:
Terminate the current line. If there are no characters other than autoindent
characters on the line, all characters on the line shall be discarded.
Prompt for text input on a new line after the current line. If the autoindent edit
option is set, an appropriate number of autoindent characters shall be added as a
prefix to the line as described by the ex autoindent edit option.
<backslash>
Synopsis:
<backslash>
Allow the entry of a subsequent <newline> or <control>‐J as a literal character, removing
any special meaning that it may have to the editor during text input mode. The <backslash>
character shall be retained and evaluated when the command line is parsed, or retained and
included when the input text becomes part of the edit buffer.
<control>‐V
Synopsis:
<control>-V
Allow the entry of any subsequent character as a literal character, removing any special
meaning that it may have to the editor during text input mode. The <control>‐V character
shall be discarded before the command line is parsed or the input text becomes part of the
edit buffer.
If the ``literal next'' functionality is performed by the underlying system, it is
implementation-defined whether a character other than <control>‐V performs this function.
<control>‐W
Synopsis:
<control>-W
Discard the <control>‐W, and the word previous to it in the input line, including any
<blank> characters following the word and preceding the <control>‐W. If the ``word
erase'' functionality is performed by the underlying system, it is implementation-defined
whether a character other than <control>‐W performs this function.
Command Descriptions in ex
The following symbols are used in this section to represent command modifiers. Some of
these modifiers can be omitted, in which case the specified defaults shall be used.
1addr A single line address, given in any of the forms described in Addressing in ex;
the default shall be the current line ('.'), unless otherwise specified.
If the line address is zero, it shall be an error, unless otherwise specified in
the following command descriptions.
If the edit buffer is empty, and the address is specified with a command other
than =, append, insert, open, put, read, or visual, or the address is not zero,
it shall be an error.
2addr Two addresses specifying an inclusive range of lines. If no addresses are
specified, the default for 2addr shall be the current line only (".,."), unless
otherwise specified in the following command descriptions. If one address is
specified, 2addr shall specify that line only, unless otherwise specified in the
following command descriptions.
It shall be an error if the first address is greater than the second address.
If the edit buffer is empty, and the two addresses are specified with a command
other than the !, write, wq, or xit commands, or either address is not zero, it
shall be an error.
count A positive decimal number. If count is specified, it shall be equivalent to
specifying an additional address to the command, unless otherwise specified by
the following command descriptions. The additional address shall be equal to the
last address specified to the command (either explicitly or by default) plus
count-1.
If this would result in an address greater than the last line of the edit
buffer, it shall be corrected to equal the last line of the edit buffer.
flags One or more of the characters '+', '-', '#', 'p', or 'l' (ell). The flag
characters can be <blank>-separated, and in any order or combination. The
characters '#', 'p', and 'l' shall cause lines to be written in the format
specified by the print command with the specified flags.
The lines to be written are as follows:
1. All edit buffer lines written during the execution of the ex &, ~, list,
number, open, print, s, visual, and z commands shall be written as specified
by flags.
2. After the completion of an ex command with a flag as an argument, the
current line shall be written as specified by flags, unless the current line
was the last line written by the command.
The characters '+' and '-' cause the value of the current line after the
execution of the ex command to be adjusted by the offset address as described in
Addressing in ex. This adjustment shall occur before the current line is
written as described in 2. above.
The default for flags shall be none.
buffer One of a number of named areas for holding text. The named buffers are specified
by the alphanumeric characters of the POSIX locale. There shall also be one
``unnamed'' buffer. When no buffer is specified for editor commands that use a
buffer, the unnamed buffer shall be used. Commands that store text into buffers
shall store the text as it was before the command took effect, and shall store
text occurring earlier in the file before text occurring later in the file,
regardless of how the text region was specified. Commands that store text into
buffers shall store the text into the unnamed buffer as well as any specified
buffer.
In ex commands, buffer names are specified as the name by itself. In open or
visual mode commands the name is preceded by a double-quote ('"') character.
If the specified buffer name is an uppercase character, and the buffer contents
are to be modified, the buffer shall be appended to rather than being
overwritten. If the buffer is not being modified, specifying the buffer name in
lowercase and uppercase shall have identical results.
There shall also be buffers named by the numbers 1 through 9. In open and visual
mode, if a region of text including characters from more than a single line is
being modified by the vi c or d commands, the motion character associated with
the c or d commands specifies that the buffer text shall be in line mode, or the
commands %, `, /, ?, (, ), N, n, {, or } are used to define a region of text for
the c or d commands, the contents of buffers 1 through 8 shall be moved into the
buffer named by the next numerically greater value, the contents of buffer 9
shall be discarded, and the region of text shall be copied into buffer 1. This
shall be in addition to copying the text into a user-specified buffer or unnamed
buffer, or both. Numeric buffers can be specified as a source buffer for open
and visual mode commands; however, specifying a numeric buffer as the write
target of an open or visual mode command shall have unspecified results.
The text of each buffer shall have the characteristic of being in either line or
character mode. Appending text to a non-empty buffer shall set the mode to match
the characteristic of the text being appended. Appending text to a buffer shall
cause the creation of at least one additional line in the buffer. All text
stored into buffers by ex commands shall be in line mode. The ex commands that
use buffers as the source of text specify individually how buffers of different
modes are handled. Each open or visual mode command that uses buffers for any
purpose specifies individually the mode of the text stored into the buffer and
how buffers of different modes are handled.
file Command text used to derive a pathname. The default shall be the current
pathname, as defined previously, in which case, if no current pathname has yet
been established it shall be an error, except where specifically noted in the
individual command descriptions that follow. If the command text contains any
of the characters '~', '{', '[', '*', '?', '$', '"', backquote, single-quote,
and <backslash>, it shall be subjected to the process of ``shell expansions'',
as described below; if more than a single pathname results and the command
expects only one, it shall be an error.
The process of shell expansions in the editor shall be done as follows. The ex
utility shall pass two arguments to the program named by the shell edit option;
the first shall be -c, and the second shall be the string "echo" and the command
text as a single argument. The standard output and standard error of that
command shall replace the command text.
! A character that can be appended to the command name to modify its operation, as
detailed in the individual command descriptions. With the exception of the ex
read, write, and ! commands, the '!' character shall only act as a modifier if
there are no <blank> characters between it and the command name.
remembered search direction
The vi commands N and n begin searching in a forwards or backwards direction in
the edit buffer based on a remembered search direction, which is initially
unset, and is set by the ex global, v, s, and tag commands, and the vi / and ?
commands.
Abbreviate
Synopsis:
ab[breviate][lhs rhs]
If lhs and rhs are not specified, write the current list of abbreviations and do nothing
more.
Implementations may restrict the set of characters accepted in lhs or rhs, except that
printable characters and <blank> characters shall not be restricted. Additional
restrictions shall be implementation-defined.
In both lhs and rhs, any character may be escaped with a <control>‐V, in which case the
character shall not be used to delimit lhs from rhs, and the escaping <control>‐V shall be
discarded.
In open and visual text input mode, if a non-word or <ESC> character that is not escaped
by a <control>‐V character is entered after a word character, a check shall be made for a
set of characters matching lhs, in the text input entered during this command. If it is
found, the effect shall be as if rhs was entered instead of lhs.
The set of characters that are checked is defined as follows:
1. If there are no characters inserted before the word and non-word or <ESC> characters
that triggered the check, the set of characters shall consist of the word character.
2. If the character inserted before the word and non-word or <ESC> characters that
triggered the check is a word character, the set of characters shall consist of the
characters inserted immediately before the triggering characters that are word
characters, plus the triggering word character.
3. If the character inserted before the word and non-word or <ESC> characters that
triggered the check is not a word character, the set of characters shall consist of
the characters that were inserted before the triggering characters that are neither
<blank> characters nor word characters, plus the triggering word character.
It is unspecified whether the lhs argument entered for the ex abbreviate and unabbreviate
commands is replaced in this fashion. Regardless of whether or not the replacement occurs,
the effect of the command shall be as if the replacement had not occurred.
Current line: Unchanged.
Current column: Unchanged.
Append
Synopsis:
[1addr] a[ppend][!]
Enter ex text input mode; the input text shall be placed after the specified line. If line
zero is specified, the text shall be placed at the beginning of the edit buffer.
This command shall be affected by the number and autoindent edit options; following the
command name with '!' shall cause the autoindent edit option setting to be toggled for
the duration of this command only.
Current line: Set to the last input line; if no lines were input, set to the specified
line, or to the first line of the edit buffer if a line of zero was specified, or zero if
the edit buffer is empty.
Current column: Set to non-<blank>.
Arguments
Synopsis:
ar[gs]
Write the current argument list, with the current argument-list entry, if any, between '['
and ']' characters.
Current line: Unchanged.
Current column: Unchanged.
Change
Synopsis:
[2addr] c[hange][!][count]
Enter ex text input mode; the input text shall replace the specified lines. The specified
lines shall be copied into the unnamed buffer, which shall become a line mode buffer.
This command shall be affected by the number and autoindent edit options; following the
command name with '!' shall cause the autoindent edit option setting to be toggled for
the duration of this command only.
Current line: Set to the last input line; if no lines were input, set to the line before
the first address, or to the first line of the edit buffer if there are no lines preceding
the first address, or to zero if the edit buffer is empty.
Current column: Set to non-<blank>.
Change Directory
Synopsis:
chd[ir][!][directory]
cd[!][directory]
Change the current working directory to directory.
If no directory argument is specified, and the HOME environment variable is set to a non-
null and non-empty value, directory shall default to the value named in the HOME
environment variable. If the HOME environment variable is empty or is undefined, the
default value of directory is implementation-defined.
If no '!' is appended to the command name, and the edit buffer has been modified since
the last complete write, and the current pathname does not begin with a '/', it shall be
an error.
Current line: Unchanged.
Current column: Unchanged.
Copy
Synopsis:
[2addr] co[py] 1addr [flags]
[2addr] t 1addr [flags]
Copy the specified lines after the specified destination line; line zero specifies that
the lines shall be placed at the beginning of the edit buffer.
Current line: Set to the last line copied.
Current column: Set to non-<blank>.
Delete
Synopsis:
[2addr] d[elete][buffer][count][flags]
Delete the specified lines into a buffer (defaulting to the unnamed buffer), which shall
become a line-mode buffer.
Flags can immediately follow the command name; see Command Line Parsing in ex.
Current line: Set to the line following the deleted lines, or to the last line in the edit
buffer if that line is past the end of the edit buffer, or to zero if the edit buffer is
empty.
Current column: Set to non-<blank>.
Edit
Synopsis:
e[dit][!][+command][file]
ex[!][+command][file]
If no '!' is appended to the command name, and the edit buffer has been modified since
the last complete write, it shall be an error.
If file is specified, replace the current contents of the edit buffer with the current
contents of file, and set the current pathname to file. If file is not specified, replace
the current contents of the edit buffer with the current contents of the file named by the
current pathname. If for any reason the current contents of the file cannot be accessed,
the edit buffer shall be empty.
The +command option shall be <blank>-delimited; <blank> characters within the +command can
be escaped by preceding them with a <backslash> character. The +command shall be
interpreted as an ex command immediately after the contents of the edit buffer have been
replaced and the current line and column have been set.
If the edit buffer is empty:
Current line: Set to 0.
Current column: Set to 1.
Otherwise, if executed while in ex command mode or if the +command argument is specified:
Current line: Set to the last line of the edit buffer.
Current column: Set to non-<blank>.
Otherwise, if file is omitted or results in the current pathname:
Current line: Set to the first line of the edit buffer.
Current column: Set to non-<blank>.
Otherwise, if file is the same as the last file edited, the line and column shall be set
as follows; if the file was previously edited, the line and column may be set as follows:
Current line: Set to the last value held when that file was last edited. If this value is
not a valid line in the new edit buffer, set to the first line of the edit buffer.
Current column: If the current line was set to the last value held when the file was last
edited, set to the last value held when the file was last edited. Otherwise, or if the
last value is not a valid column in the new edit buffer, set to non-<blank>.
Otherwise:
Current line: Set to the first line of the edit buffer.
Current column: Set to non-<blank>.
File
Synopsis:
f[ile][file]
If a file argument is specified, the alternate pathname shall be set to the current
pathname, and the current pathname shall be set to file.
Write an informational message. If the file has a current pathname, it shall be included
in this message; otherwise, the message shall indicate that there is no current pathname.
If the edit buffer contains lines, the current line number and the number of lines in the
edit buffer shall be included in this message; otherwise, the message shall indicate that
the edit buffer is empty. If the edit buffer has been modified since the last complete
write, this fact shall be included in this message. If the readonly edit option is set,
this fact shall be included in this message. The message may contain other unspecified
information.
Current line: Unchanged.
Current column: Unchanged.
Global
Synopsis:
[2addr] g[lobal] /pattern/ [commands]
[2addr] v /pattern/ [commands]
The optional '!' character after the global command shall be the same as executing the v
command.
If pattern is empty (for example, "//") or not specified, the last regular expression used
in the editor command shall be used as the pattern. The pattern can be delimited by
<slash> characters (shown in the Synopsis), as well as any non-alphanumeric or non-<blank>
other than <backslash>, <vertical-line>, <newline>, or double-quote.
If no lines are specified, the lines shall default to the entire file.
The global and v commands are logically two-pass operations. First, mark the lines within
the specified lines for which the line excluding the terminating <newline> matches
(global) or does not match (v or global!) the specified pattern. Second, execute the ex
commands given by commands, with the current line ('.') set to each marked line. If an
error occurs during this process, or the contents of the edit buffer are replaced (for
example, by the ex :edit command) an error message shall be written and no more commands
resulting from the execution of this command shall be processed.
Multiple ex commands can be specified by entering multiple commands on a single line using
a <vertical-line> to delimit them, or one per line, by escaping each <newline> with a
<backslash>.
If no commands are specified:
1. If in ex command mode, it shall be as if the print command were specified.
2. Otherwise, no command shall be executed.
For the append, change, and insert commands, the input text shall be included as part of
the command, and the terminating <period> can be omitted if the command ends the list of
commands. The open and visual commands can be specified as one of the commands, in which
case each marked line shall cause the editor to enter open or visual mode. If open or
visual mode is exited using the vi Q command, the current line shall be set to the next
marked line, and open or visual mode reentered, until the list of marked lines is
exhausted.
The global, v, and undo commands cannot be used in commands. Marked lines may be deleted
by commands executed for lines occurring earlier in the file than the marked lines. In
this case, no commands shall be executed for the deleted lines.
If the remembered search direction is not set, the global and v commands shall set it to
forward.
The autoprint and autoindent edit options shall be inhibited for the duration of the g or
v command.
Current line: If no commands executed, set to the last marked line. Otherwise, as
specified for the executed ex commands.
Current column: If no commands are executed, set to non-<blank>; otherwise, as specified
for the individual ex commands.
Insert
Synopsis:
[1addr] i[nsert][!]
Enter ex text input mode; the input text shall be placed before the specified line. If the
line is zero or 1, the text shall be placed at the beginning of the edit buffer.
This command shall be affected by the number and autoindent edit options; following the
command name with '!' shall cause the autoindent edit option setting to be toggled for
the duration of this command only.
Current line: Set to the last input line; if no lines were input, set to the line before
the specified line, or to the first line of the edit buffer if there are no lines
preceding the specified line, or zero if the edit buffer is empty.
Current column: Set to non-<blank>.
Join
Synopsis:
[2addr] j[oin][!][count][flags]
If count is specified:
If no address was specified, the join command shall behave as if 2addr were the
current line and the current line plus count (.,. + count).
If one address was specified, the join command shall behave as if 2addr were the
specified address and the specified address plus count (addr,addr + count).
If two addresses were specified, the join command shall behave as if an additional
address, equal to the last address plus count -1 (addr1,addr2,addr2 + count -1),
was specified.
If this would result in a second address greater than the last line of the edit
buffer, it shall be corrected to be equal to the last line of the edit buffer.
If no count is specified:
If no address was specified, the join command shall behave as if 2addr were the
current line and the next line (.,. +1).
If one address was specified, the join command shall behave as if 2addr were the
specified address and the next line (addr,addr +1).
Join the text from the specified lines together into a single line, which shall replace
the specified lines.
If a '!' character is appended to the command name, the join shall be without
modification of any line, independent of the current locale.
Otherwise, in the POSIX locale, set the current line to the first of the specified lines,
and then, for each subsequent line, proceed as follows:
1. Discard leading <space> characters from the line to be joined.
2. If the line to be joined is now empty, delete it, and skip steps 3 through 5.
3. If the current line ends in a <blank>, or the first character of the line to be joined
is a ')' character, join the lines without further modification.
4. If the last character of the current line is a '.', join the lines with two <space>
characters between them.
5. Otherwise, join the lines with a single <space> between them.
Current line: Set to the first line specified.
Current column: Set to non-<blank>.
List
Synopsis:
[2addr] l[ist][count][flags]
This command shall be equivalent to the ex command:
[2addr] p[rint][count] l[flags]
See Print.
Map
Synopsis:
map[!][lhs rhs]
If lhs and rhs are not specified:
1. If '!' is specified, write the current list of text input mode maps.
2. Otherwise, write the current list of command mode maps.
3. Do nothing more.
Implementations may restrict the set of characters accepted in lhs or rhs, except that
printable characters and <blank> characters shall not be restricted. Additional
restrictions shall be implementation-defined. In both lhs and rhs, any character can be
escaped with a <control>‐V, in which case the character shall not be used to delimit lhs
from rhs, and the escaping <control>‐V shall be discarded.
If the character '!' is appended to the map command name, the mapping shall be effective
during open or visual text input mode rather than open or visual command mode. This allows
lhs to have two different map definitions at the same time: one for command mode and one
for text input mode.
For command mode mappings:
When the lhs is entered as any part of a vi command in open or visual mode (but not
as part of the arguments to the command), the action shall be as if the
corresponding rhs had been entered.
If any character in the command, other than the first, is escaped using a
<control>‐V character, that character shall not be part of a match to an lhs.
It is unspecified whether implementations shall support map commands where the lhs
is more than a single character in length, where the first character of the lhs is
printable.
If lhs contains more than one character and the first character is '#', followed by
a sequence of digits corresponding to a numbered function key, then when this
function key is typed it shall be mapped to rhs. Characters other than digits
following a '#' character also represent the function key named by the characters
in the lhs following the '#' and may be mapped to rhs. It is unspecified how
function keys are named or what function keys are supported.
For text input mode mappings:
When the lhs is entered as any part of text entered in open or visual text input
modes, the action shall be as if the corresponding rhs had been entered.
If any character in the input text is escaped using a <control>‐V character, that
character shall not be part of a match to an lhs.
It is unspecified whether the lhs text entered for subsequent map or unmap commands
is replaced with the rhs text for the purposes of the screen display; regardless of
whether or not the display appears as if the corresponding rhs text was entered,
the effect of the command shall be as if the lhs text was entered.
If only part of the lhs is entered, it is unspecified how long the editor will wait for
additional, possibly matching characters before treating the already entered characters as
not matching the lhs.
The rhs characters shall themselves be subject to remapping, unless otherwise specified by
the remap edit option, except that if the characters in lhs occur as prefix characters in
rhs, those characters shall not be remapped.
On block-mode terminals, the mapping need not occur immediately (for example, it may occur
after the terminal transmits a group of characters to the system), but it shall achieve
the same results as if it occurred immediately.
Current line: Unchanged.
Current column: Unchanged.
Mark
Synopsis:
[1addr] ma[rk] character
[1addr] k character
Implementations shall support character values of a single lowercase letter of the POSIX
locale and the backquote and single-quote characters; support of other characters is
implementation-defined.
If executing the vi m command, set the specified mark to the current line and 1-based
numbered character referenced by the current column, if any; otherwise, column position 1.
Otherwise, set the specified mark to the specified line and 1-based numbered first
non-<blank> non-<newline> in the line, if any; otherwise, the last non-<newline> in the
line, if any; otherwise, column position 1.
The mark shall remain associated with the line until the mark is reset or the line is
deleted. If a deleted line is restored by a subsequent undo command, any marks previously
associated with the line, which have not been reset, shall be restored as well. Any use of
a mark not associated with a current line in the edit buffer shall be an error.
The marks ` and ' shall be set as described previously, immediately before the following
events occur in the editor:
1. The use of '$' as an ex address
2. The use of a positive decimal number as an ex address
3. The use of a search command as an ex address
4. The use of a mark reference as an ex address
5. The use of the following open and visual mode commands: <control>‐], %, (, ), [, ], {,
}
6. The use of the following open and visual mode commands: ', G, H, L, M, z if the
current line will change as a result of the command
7. The use of the open and visual mode commands: /, ?, N, `, n if the current line or
column will change as a result of the command
8. The use of the ex mode commands: z, undo, global, v
For rules 1., 2., 3., and 4., the ` and ' marks shall not be set if the ex command is
parsed as specified by rule 6.a. in Command Line Parsing in ex.
For rules 5., 6., and 7., the ` and ' marks shall not be set if the commands are used as
motion commands in open and visual mode.
For rules 1., 2., 3., 4., 5., 6., 7., and 8., the ` and ' marks shall not be set if the
command fails.
The ` and ' marks shall be set as described previously, each time the contents of the edit
buffer are replaced (including the editing of the initial buffer), if in open or visual
mode, or if in ex mode and the edit buffer is not empty, before any commands or movements
(including commands or movements specified by the -c or -t options or the +command
argument) are executed on the edit buffer. If in open or visual mode, the marks shall be
set as if executing the vi m command; otherwise, as if executing the ex mark command.
When changing from ex mode to open or visual mode, if the ` and ' marks are not already
set, the ` and ' marks shall be set as described previously.
Current line: Unchanged.
Current column: Unchanged.
Move
Synopsis:
[2addr] m[ove] 1addr [flags]
Move the specified lines after the specified destination line. A destination of line zero
specifies that the lines shall be placed at the beginning of the edit buffer. It shall be
an error if the destination line is within the range of lines to be moved.
Current line: Set to the last of the moved lines.
Current column: Set to non-<blank>.
Next
Synopsis:
n[ext][!][+command][file ...]
If no '!' is appended to the command name, and the edit buffer has been modified since
the last complete write, it shall be an error, unless the file is successfully written as
specified by the autowrite option.
If one or more files is specified:
1. Set the argument list to the specified filenames.
2. Set the current argument list reference to be the first entry in the argument list.
3. Set the current pathname to the first filename specified.
Otherwise:
1. It shall be an error if there are no more filenames in the argument list after the
filename currently referenced.
2. Set the current pathname and the current argument list reference to the filename after
the filename currently referenced in the argument list.
Replace the contents of the edit buffer with the contents of the file named by the current
pathname. If for any reason the contents of the file cannot be accessed, the edit buffer
shall be empty.
This command shall be affected by the autowrite and writeany edit options.
The +command option shall be <blank>-delimited; <blank> characters can be escaped by
preceding them with a <backslash> character. The +command shall be interpreted as an ex
command immediately after the contents of the edit buffer have been replaced and the
current line and column have been set.
Current line: Set as described for the edit command.
Current column: Set as described for the edit command.
Number
Synopsis:
[2addr] nu[mber][count][flags]
[2addr] #[count][flags]
These commands shall be equivalent to the ex command:
[2addr] p[rint][count] #[flags]
See Print.
Open
Synopsis:
[1addr] o[pen] /pattern/ [flags]
This command need not be supported on block-mode terminals or terminals with insufficient
capabilities. If standard input, standard output, or standard error are not terminal
devices, the results are unspecified.
Enter open mode.
The trailing delimiter can be omitted from pattern at the end of the command line. If
pattern is empty (for example, "//") or not specified, the last regular expression used in
the editor shall be used as the pattern. The pattern can be delimited by <slash>
characters (shown in the Synopsis), as well as any alphanumeric, or non-<blank> other than
<backslash>, <vertical-line>, <newline>, or double-quote.
Current line: Set to the specified line.
Current column: Set to non-<blank>.
Preserve
Synopsis:
pre[serve]
Save the edit buffer in a form that can later be recovered by using the -r option or by
using the ex recover command. After the file has been preserved, a mail message shall be
sent to the user. This message shall be readable by invoking the mailx utility. The
message shall contain the name of the file, the time of preservation, and an ex command
that could be used to recover the file. Additional information may be included in the mail
message.
Current line: Unchanged.
Current column: Unchanged.
Print
Synopsis:
[2addr] p[rint][count][flags]
Write the addressed lines. The behavior is unspecified if the number of columns on the
display is less than the number of columns required to write any single character in the
lines being written.
Non-printable characters, except for the <tab>, shall be written as implementation-defined
multi-character sequences.
If the # flag is specified or the number edit option is set, each line shall be preceded
by its line number in the following format:
"%6d ", <line number>
If the l flag is specified or the list edit option is set:
1. The characters listed in the Base Definitions volume of POSIX.1‐2017, Table 5-1,
Escape Sequences and Associated Actions shall be written as the corresponding escape
sequence.
2. Non-printable characters not in the Base Definitions volume of POSIX.1‐2017, Table
5-1, Escape Sequences and Associated Actions shall be written as one three-digit octal
number (with a preceding <backslash>) for each byte in the character (most significant
byte first).
3. The end of each line shall be marked with a '$', and literal '$' characters within the
line shall be written with a preceding <backslash>.
Long lines shall be folded; the length at which folding occurs is unspecified, but should
be appropriate for the output terminal, considering the number of columns of the terminal.
If a line is folded, and the l flag is not specified and the list edit option is not set,
it is unspecified whether a multi-column character at the folding position is separated;
it shall not be discarded.
Current line: Set to the last written line.
Current column: Unchanged if the current line is unchanged; otherwise, set to non-<blank>.
Put
Synopsis:
[1addr] pu[t][buffer]
Append text from the specified buffer (by default, the unnamed buffer) to the specified
line; line zero specifies that the text shall be placed at the beginning of the edit
buffer. Each portion of a line in the buffer shall become a new line in the edit buffer,
regardless of the mode of the buffer.
Current line: Set to the last line entered into the edit buffer.
Current column: Set to non-<blank>.
Quit
Synopsis:
q[uit][!]
If no '!' is appended to the command name:
1. If the edit buffer has been modified since the last complete write, it shall be an
error.
2. If there are filenames in the argument list after the filename currently referenced,
and the last command was not a quit, wq, xit, or ZZ (see Exit) command, it shall be an
error.
Otherwise, terminate the editing session.
Read
Synopsis:
[1addr] r[ead][!][file]
If '!' is not the first non-<blank> to follow the command name, a copy of the specified
file shall be appended into the edit buffer after the specified line; line zero specifies
that the copy shall be placed at the beginning of the edit buffer. The number of lines and
bytes read shall be written. If no file is named, the current pathname shall be the
default. If there is no current pathname, then file shall become the current pathname. If
there is no current pathname or file operand, it shall be an error. Specifying a file that
is not of type regular shall have unspecified results.
Otherwise, if file is preceded by '!', the rest of the line after the '!' shall have '%',
'#', and '!' characters expanded as described in Command Line Parsing in ex.
The ex utility shall then pass two arguments to the program named by the shell edit
option; the first shall be -c and the second shall be the expanded arguments to the read
command as a single argument. The standard input of the program shall be set to the
standard input of the ex program when it was invoked. The standard error and standard
output of the program shall be appended into the edit buffer after the specified line.
Each line in the copied file or program output (as delimited by <newline> characters or
the end of the file or output if it is not immediately preceded by a <newline>), shall be
a separate line in the edit buffer. Any occurrences of <carriage-return> and <newline>
pairs in the output shall be treated as single <newline> characters.
The special meaning of the '!' following the read command can be overridden by escaping
it with a <backslash> character.
Current line: If no lines are added to the edit buffer, unchanged. Otherwise, if in open
or visual mode, set to the first line entered into the edit buffer. Otherwise, set to the
last line entered into the edit buffer.
Current column: Set to non-<blank>.
Recover
Synopsis:
rec[over][!] file
If no '!' is appended to the command name, and the edit buffer has been modified since
the last complete write, it shall be an error.
If no file operand is specified, then the current pathname shall be used. If there is no
current pathname or file operand, it shall be an error.
If no recovery information has previously been saved about file, the recover command shall
behave identically to the edit command, and an informational message to this effect shall
be written.
Otherwise, set the current pathname to file, and replace the current contents of the edit
buffer with the recovered contents of file. If there are multiple instances of the file
to be recovered, the one most recently saved shall be recovered, and an informational
message that there are previous versions of the file that can be recovered shall be
written. The editor shall behave as if the contents of the edit buffer have already been
modified.
Current file: Set as described for the edit command.
Current column: Set as described for the edit command.
Rewind
Synopsis:
rew[ind][!]
If no '!' is appended to the command name, and the edit buffer has been modified since
the last complete write, it shall be an error, unless the file is successfully written as
specified by the autowrite option.
If the argument list is empty, it shall be an error.
The current argument list reference and the current pathname shall be set to the first
filename in the argument list.
Replace the contents of the edit buffer with the contents of the file named by the current
pathname. If for any reason the contents of the file cannot be accessed, the edit buffer
shall be empty.
This command shall be affected by the autowrite and writeany edit options.
Current line: Set as described for the edit command.
Current column: Set as described for the edit command.
Set
Synopsis:
se[t][option[=[value]] ...][nooption ...][option? ...][all]
When no arguments are specified, write the value of the term edit option and those options
whose values have been changed from the default settings; when the argument all is
specified, write all of the option values.
Giving an option name followed by the character '?' shall cause the current value of that
option to be written. The '?' can be separated from the option name by zero or more
<blank> characters. The '?' shall be necessary only for Boolean valued options. Boolean
options can be given values by the form set option to turn them on or set nooption to turn
them off; string and numeric options can be assigned by the form set option=value. Any
<blank> characters in strings can be included as is by preceding each <blank> with an
escaping <backslash>. More than one option can be set or listed by a single set command
by specifying multiple arguments, each separated from the next by one or more <blank>
characters.
See Edit Options in ex for details about specific options.
Current line: Unchanged.
Current column: Unchanged.
Shell
Synopsis:
sh[ell]
Invoke the program named in the shell edit option with the single argument -i (interactive
mode). Editing shall be resumed when the program exits.
Current line: Unchanged.
Current column: Unchanged.
Source
Synopsis:
so[urce] file
Read and execute ex commands from file. Lines in the file that are blank lines shall be
ignored.
Current line: As specified for the individual ex commands.
Current column: As specified for the individual ex commands.
Substitute
Synopsis:
[2addr] s[ubstitute][/pattern/repl/[options][count][flags]]
[2addr] &[options][count][flags]]
[2addr] ~[options][count][flags]]
Replace the first instance of the pattern pattern by the string repl on each specified
line. (See Regular Expressions in ex and Replacement Strings in ex.) Any non-alphabetic,
non-<blank> delimiter other than <backslash>, '|', <newline>, or double-quote can be used
instead of '/'. <backslash> characters can be used to escape delimiters, <backslash>
characters, and other special characters.
The trailing delimiter can be omitted from pattern or from repl at the end of the command
line. If both pattern and repl are not specified or are empty (for example, "//"), the
last s command shall be repeated. If only pattern is not specified or is empty, the last
regular expression used in the editor shall be used as the pattern. If only repl is not
specified or is empty, the pattern shall be replaced by nothing. If the entire
replacement pattern is '%', the last replacement pattern to an s command shall be used.
Entering a <carriage-return> in repl (which requires an escaping <backslash> in ex mode
and an escaping <control>‐V in open or vi mode) shall split the line at that point,
creating a new line in the edit buffer. The <carriage-return> shall be discarded.
If options includes the letter 'g' (global), all non-overlapping instances of the pattern
in the line shall be replaced.
If options includes the letter 'c' (confirm), then before each substitution the line shall
be written; the written line shall reflect all previous substitutions. On the following
line, <space> characters shall be written beneath the characters from the line that are
before the pattern to be replaced, and '^' characters written beneath the characters
included in the pattern to be replaced. The ex utility shall then wait for a response from
the user. An affirmative response shall cause the substitution to be done, while any other
input shall not make the substitution. An affirmative response shall consist of a line
with the affirmative response (as defined by the current locale) at the beginning of the
line. This line shall be subject to editing in the same way as the ex command line.
If interrupted (see the ASYNCHRONOUS EVENTS section), any modifications confirmed by the
user shall be preserved in the edit buffer after the interrupt.
If the remembered search direction is not set, the s command shall set it to forward.
In the second Synopsis, the & command shall repeat the previous substitution, as if the &
command were replaced by:
s/pattern/repl/
where pattern and repl are as specified in the previous s, &, or ~ command.
In the third Synopsis, the ~ command shall repeat the previous substitution, as if the '~'
were replaced by:
s/pattern/repl/
where pattern shall be the last regular expression specified to the editor, and repl shall
be from the previous substitution (including & and ~) command.
These commands shall be affected by the LC_MESSAGES environment variable.
Current line: Set to the last line in which a substitution occurred, or, unchanged if no
substitution occurred.
Current column: Set to non-<blank>.
Suspend
Synopsis:
su[spend][!]
st[op][!]
Allow control to return to the invoking process; ex shall suspend itself as if it had
received the SIGTSTP signal. The suspension shall occur only if job control is enabled in
the invoking shell (see the description of set -m).
These commands shall be affected by the autowrite and writeany edit options.
The current susp character (see stty) shall be equivalent to the suspend command.
Tag
Synopsis:
ta[g][!] tagstring
The results are unspecified if the format of a tags file is not as specified by the ctags
utility (see ctags) description.
The tag command shall search for tagstring in the tag files referred to by the tag edit
option, in the order they are specified, until a reference to tagstring is found. Files
shall be searched from beginning to end. If no reference is found, it shall be an error
and an error message to this effect shall be written. If the reference is not found, or if
an error occurs while processing a file referred to in the tag edit option, it shall be an
error, and an error message shall be written at the first occurrence of such an error.
Otherwise, if the tags file contained a pattern, the pattern shall be treated as a regular
expression used in the editor; for example, for the purposes of the s command.
If the tagstring is in a file with a different name than the current pathname, set the
current pathname to the name of that file, and replace the contents of the edit buffer
with the contents of that file. In this case, if no '!' is appended to the command name,
and the edit buffer has been modified since the last complete write, it shall be an error,
unless the file is successfully written as specified by the autowrite option.
This command shall be affected by the autowrite, tag, taglength, and writeany edit
options.
Current line: If the tags file contained a line number, set to that line number. If the
line number is larger than the last line in the edit buffer, an error message shall be
written and the current line shall be set as specified for the edit command.
If the tags file contained a pattern, set to the first occurrence of the pattern in the
file. If no matching pattern is found, an error message shall be written and the current
line shall be set as specified for the edit command.
Current column: If the tags file contained a line-number reference and that line-number
was not larger than the last line in the edit buffer, or if the tags file contained a
pattern and that pattern was found, set to non-<blank>. Otherwise, set as specified for
the edit command.
Unabbreviate
Synopsis:
una[bbrev] lhs
If lhs is not an entry in the current list of abbreviations (see Abbreviate), it shall be
an error. Otherwise, delete lhs from the list of abbreviations.
Current line: Unchanged.
Current column: Unchanged.
Undo
Synopsis:
u[ndo]
Reverse the changes made by the last command that modified the contents of the edit
buffer, including undo. For this purpose, the global, v, open, and visual commands, and
commands resulting from buffer executions and mapped character expansions, are considered
single commands.
If no action that can be undone preceded the undo command, it shall be an error.
If the undo command restores lines that were marked, the mark shall also be restored
unless it was reset subsequent to the deletion of the lines.
Current line:
1. If lines are added or changed in the file, set to the first line added or changed.
2. Set to the line before the first line deleted, if it exists.
3. Set to 1 if the edit buffer is not empty.
4. Set to zero.
Current column: Set to non-<blank>.
Unmap
Synopsis:
unm[ap][!] lhs
If '!' is appended to the command name, and if lhs is not an entry in the list of text
input mode map definitions, it shall be an error. Otherwise, delete lhs from the list of
text input mode map definitions.
If no '!' is appended to the command name, and if lhs is not an entry in the list of
command mode map definitions, it shall be an error. Otherwise, delete lhs from the list of
command mode map definitions.
Current line: Unchanged.
Current column: Unchanged.
Version
Synopsis:
ve[rsion]
Write a message containing version information for the editor. The format of the message
is unspecified.
Current line: Unchanged.
Current column: Unchanged.
Visual
Synopsis:
[1addr] vi[sual][type][count][flags]
If ex is currently in open or visual mode, the Synopsis and behavior of the visual command
shall be the same as the edit command, as specified by Edit.
Otherwise, this command need not be supported on block-mode terminals or terminals with
insufficient capabilities. If standard input, standard output, or standard error are not
terminal devices, the results are unspecified.
If count is specified, the value of the window edit option shall be set to count (as
described in window). If the '^' type character was also specified, the window edit
option shall be set before being used by the type character.
Enter visual mode. If type is not specified, it shall be as if a type of '+' was
specified. The type shall cause the following effects:
+ Place the beginning of the specified line at the top of the display.
- Place the end of the specified line at the bottom of the display.
. Place the beginning of the specified line in the middle of the display.
^ If the specified line is less than or equal to the value of the window edit option,
set the line to 1; otherwise, decrement the line by the value of the window edit
option minus 1. Place the beginning of this line as close to the bottom of the
displayed lines as possible, while still displaying the value of the window edit
option number of lines.
Current line: Set to the specified line.
Current column: Set to non-<blank>.
Write
Synopsis:
[2addr] w[rite][!][>>][file]
[2addr] w[rite][!][file]
[2addr] wq[!][>>][file]
If no lines are specified, the lines shall default to the entire file.
The command wq shall be equivalent to a write command followed by a quit command; wq!
shall be equivalent to write! followed by quit. In both cases, if the write command
fails, the quit shall not be attempted.
If the command name is not followed by one or more <blank> characters, or file is not
preceded by a '!' character, the write shall be to a file.
1. If the >> argument is specified, and the file already exists, the lines shall be
appended to the file instead of replacing its contents. If the >> argument is
specified, and the file does not already exist, it is unspecified whether the write
shall proceed as if the >> argument had not been specified or if the write shall fail.
2. If the readonly edit option is set (see readonly), the write shall fail.
3. If file is specified, and is not the current pathname, and the file exists, the write
shall fail.
4. If file is not specified, the current pathname shall be used. If there is no current
pathname, the write command shall fail.
5. If the current pathname is used, and the current pathname has been changed by the file
or read commands, and the file exists, the write shall fail. If the write is
successful, subsequent writes shall not fail for this reason (unless the current
pathname is changed again).
6. If the whole edit buffer is not being written, and the file to be written exists, the
write shall fail.
For rules 1., 2., 3., and 5., the write can be forced by appending the character '!' to
the command name.
For rules 2., 3., and 5., the write can be forced by setting the writeany edit option.
Additional, implementation-defined tests may cause the write to fail.
If the edit buffer is empty, a file without any contents shall be written.
An informational message shall be written noting the number of lines and bytes written.
Otherwise, if the command is followed by one or more <blank> characters, and the file is
preceded by '!', the rest of the line after the '!' shall have '%', '#', and '!'
characters expanded as described in Command Line Parsing in ex.
The ex utility shall then pass two arguments to the program named by the shell edit
option; the first shall be -c and the second shall be the expanded arguments to the write
command as a single argument. The specified lines shall be written to the standard input
of the command. The standard error and standard output of the program, if any, shall be
written as described for the print command. If the last character in that output is not a
<newline>, a <newline> shall be written at the end of the output.
The special meaning of the '!' following the write command can be overridden by escaping
it with a <backslash> character.
Current line: Unchanged.
Current column: Unchanged.
Write and Exit
Synopsis:
[2addr] x[it][!][file]
If the edit buffer has not been modified since the last complete write, xit shall be
equivalent to the quit command, or if a '!' is appended to the command name, to quit!.
Otherwise, xit shall be equivalent to the wq command, or if a '!' is appended to the
command name, to wq!.
Current line: Unchanged.
Current column: Unchanged.
Yank
Synopsis:
[2addr] ya[nk][buffer][count]
Copy the specified lines to the specified buffer (by default, the unnamed buffer), which
shall become a line-mode buffer.
Current line: Unchanged.
Current column: Unchanged.
Adjust Window
Synopsis:
[1addr] z[!][type ...][count][flags]
If no line is specified, the current line shall be the default; if type is omitted as
well, the current line value shall first be incremented by 1. If incrementing the current
line would cause it to be greater than the last line in the edit buffer, it shall be an
error.
If there are <blank> characters between the type argument and the preceding z command name
or optional '!' character, it shall be an error.
If count is specified, the value of the window edit option shall be set to count (as
described in window). If count is omitted, it shall default to 2 times the value of the
scroll edit option, or if ! was specified, the number of lines in the display minus 1.
If type is omitted, then count lines starting with the specified line shall be written.
Otherwise, count lines starting with the line specified by the type argument shall be
written.
The type argument shall change the lines to be written. The possible values of type are as
follows:
- The specified line shall be decremented by the following value:
(((number of '-' characters) x count) -1)
If the calculation would result in a number less than 1, it shall be an error. Write
lines from the edit buffer, starting at the new value of line, until count lines or
the last line in the edit buffer has been written.
+ The specified line shall be incremented by the following value:
(((number of '+' characters) -1) x count) +1
If the calculation would result in a number greater than the last line in the edit
buffer, it shall be an error. Write lines from the edit buffer, starting at the new
value of line, until count lines or the last line in the edit buffer has been
written.
=,. If more than a single '.' or '=' is specified, it shall be an error. The following
steps shall be taken:
1. If count is zero, nothing shall be written.
2. Write as many of the N lines before the current line in the edit buffer as
exist. If count or '!' was specified, N shall be:
(count -1) /2
Otherwise, N shall be:
(count -3) /2
If N is a number less than 3, no lines shall be written.
3. If '=' was specified as the type character, write a line consisting of the
smaller of the number of columns in the display divided by two, or 40 '-'
characters.
4. Write the current line.
5. Repeat step 3.
6. Write as many of the N lines after the current line in the edit buffer as exist.
N shall be defined as in step 2. If N is a number less than 3, no lines shall be
written. If count is less than 3, no lines shall be written.
^ The specified line shall be decremented by the following value:
(((number of '^' characters) +1) x count) -1
If the calculation would result in a number less than 1, it shall be an error. Write
lines from the edit buffer, starting at the new value of line, until count lines or
the last line in the edit buffer has been written.
Current line: Set to the last line written, unless the type is =, in which case, set to
the specified line.
Current column: Set to non-<blank>.
Escape
Synopsis:
! command
[addr]! command
The contents of the line after the '!' shall have '%', '#', and '!' characters expanded
as described in Command Line Parsing in ex. If the expansion causes the text of the line
to change, it shall be redisplayed, preceded by a single '!' character.
The ex utility shall execute the program named by the shell edit option. It shall pass two
arguments to the program; the first shall be -c, and the second shall be the expanded
arguments to the ! command as a single argument.
If no lines are specified, the standard input, standard output, and standard error of the
program shall be set to the standard input, standard output, and standard error of the ex
program when it was invoked. In addition, a warning message shall be written if the edit
buffer has been modified since the last complete write, and the warn edit option is set.
If lines are specified, they shall be passed to the program as standard input, and the
standard output and standard error of the program shall replace those lines in the edit
buffer. Each line in the program output (as delimited by <newline> characters or the end
of the output if it is not immediately preceded by a <newline>), shall be a separate line
in the edit buffer. Any occurrences of <carriage-return> and <newline> pairs in the output
shall be treated as single <newline> characters. The specified lines shall be copied into
the unnamed buffer before they are replaced, and the unnamed buffer shall become a line-
mode buffer.
If in ex mode, a single '!' character shall be written when the program completes.
This command shall be affected by the shell and warn edit options. If no lines are
specified, this command shall be affected by the autowrite and writeany edit options. If
lines are specified, this command shall be affected by the autoprint edit option.
Current line:
1. If no lines are specified, unchanged.
2. Otherwise, set to the last line read in, if any lines are read in.
3. Otherwise, set to the line before the first line of the lines specified, if that line
exists.
4. Otherwise, set to the first line of the edit buffer if the edit buffer is not empty.
5. Otherwise, set to zero.
Current column: If no lines are specified, unchanged. Otherwise, set to non-<blank>.
Shift Left
Synopsis:
[2addr] <[< ...][count][flags]
Shift the specified lines to the start of the line; the number of column positions to be
shifted shall be the number of command characters times the value of the shiftwidth edit
option. Only leading <blank> characters shall be deleted or changed into other <blank>
characters in shifting; other characters shall not be affected.
Lines to be shifted shall be copied into the unnamed buffer, which shall become a line-
mode buffer.
This command shall be affected by the autoprint edit option.
Current line: Set to the last line in the lines specified.
Current column: Set to non-<blank>.
Shift Right
Synopsis:
[2addr] >[> ...][count][flags]
Shift the specified lines away from the start of the line; the number of column positions
to be shifted shall be the number of command characters times the value of the shiftwidth
edit option. The shift shall be accomplished by adding <blank> characters as a prefix to
the line or changing leading <blank> characters into other <blank> characters. Empty lines
shall not be changed.
Lines to be shifted shall be copied into the unnamed buffer, which shall become a line-
mode buffer.
This command shall be affected by the autoprint edit option.
Current line: Set to the last line in the lines specified.
Current column: Set to non-<blank>.
<control>‐D
Synopsis:
<control>-D
Write the next n lines, where n is the minimum of the values of the scroll edit option and
the number of lines after the current line in the edit buffer. If the current line is the
last line of the edit buffer it shall be an error.
Current line: Set to the last line written.
Current column: Set to non-<blank>.
Write Line Number
Synopsis:
[1addr] = [flags]
If line is not specified, it shall default to the last line in the edit buffer. Write the
line number of the specified line.
Current line: Unchanged.
Current column: Unchanged.
Execute
Synopsis:
[2addr] @ buffer
[2addr] * buffer
If no buffer is specified or is specified as '@' or '*', the last buffer executed shall be
used. If no previous buffer has been executed, it shall be an error.
For each line specified by the addresses, set the current line ('.') to the specified
line, and execute the contents of the named buffer (as they were at the time the @ command
was executed) as ex commands. For each line of a line-mode buffer, and all but the last
line of a character-mode buffer, the ex command parser shall behave as if the line was
terminated by a <newline>.
If an error occurs during this process, or a line specified by the addresses does not
exist when the current line would be set to it, or more than a single line was specified
by the addresses, and the contents of the edit buffer are replaced (for example, by the ex
:edit command) an error message shall be written, and no more commands resulting from the
execution of this command shall be processed.
Current line: As specified for the individual ex commands.
Current column: As specified for the individual ex commands.
Regular Expressions in ex
The ex utility shall support regular expressions that are a superset of the basic regular
expressions described in the Base Definitions volume of POSIX.1‐2017, Section 9.3, Basic
Regular Expressions. A null regular expression ("//") shall be equivalent to the last
regular expression encountered.
Regular expressions can be used in addresses to specify lines and, in some commands (for
example, the substitute command), to specify portions of a line to be substituted.
The following constructs can be used to enhance the basic regular expressions:
\< Match the beginning of a word. (See the definition of word at the beginning of
Command Descriptions in ex.)
\> Match the end of a word.
~ Match the replacement part of the last substitute command. The <tilde> ('~')
character can be escaped in a regular expression to become a normal character with
no special meaning. The <backslash> shall be discarded.
When the editor option magic is not set, the only characters with special meanings shall
be '^' at the beginning of a pattern, '$' at the end of a pattern, and <backslash>. The
characters '.', '*', '[', and '~' shall be treated as ordinary characters unless preceded
by a <backslash>; when preceded by a <backslash> they shall regain their special meaning,
or in the case of <backslash>, be handled as a single <backslash>. <backslash> characters
used to escape other characters shall be discarded.
Replacement Strings in ex
The character '&' ('\&' if the editor option magic is not set) in the replacement string
shall stand for the text matched by the pattern to be replaced. The character '~' ('\~' if
magic is not set) shall be replaced by the replacement part of the previous substitute
command. The sequence '\n', where n is an integer, shall be replaced by the text matched
by the corresponding back-reference expression. If the corresponding back-reference
expression does not match, then the characters '\n' shall be replaced by the empty string.
The strings '\l', '\u', '\L', and '\U' can be used to modify the case of elements in the
replacement string (using the '\&' or "\"digit) notation. The string '\l' ('\u') shall
cause the character that follows to be converted to lowercase (uppercase). The string '\L'
('\U') shall cause all characters subsequent to it to be converted to lowercase
(uppercase) as they are inserted by the substitution until the string '\e' or '\E', or the
end of the replacement string, is encountered.
Otherwise, any character following a <backslash> shall be treated as that literal
character, and the escaping <backslash> shall be discarded.
An example of case conversion with the s command is as follows:
:p
The cat sat on the mat.
:s/\<.at\>/\u&/gp
The Cat Sat on the Mat.
:s/S\(.*\)M/S\U\1\eM/p
The Cat SAT ON THE Mat.
Edit Options in ex
The ex utility has a number of options that modify its behavior. These options have
default settings, which can be changed using the set command.
Options are Boolean unless otherwise specified.
autoindent, ai
[Default unset]
If autoindent is set, each line in input mode shall be indented (using first as many <tab>
characters as possible, as determined by the editor option tabstop, and then using <space>
characters) to align with another line, as follows:
1. If in open or visual mode and the text input is part of a line-oriented command (see
the EXTENDED DESCRIPTION in vi), align to the first column.
2. Otherwise, if in open or visual mode, indentation for each line shall be set as
follows:
a. If a line was previously inserted as part of this command, it shall be set to the
indentation of the last inserted line by default, or as otherwise specified for
the <control>‐D character in Input Mode Commands in vi.
b. Otherwise, it shall be set to the indentation of the previous current line, if
any; otherwise, to the first column.
3. For the ex a, i, and c commands, indentation for each line shall be set as follows:
a. If a line was previously inserted as part of this command, it shall be set to the
indentation of the last inserted line by default, or as otherwise specified for
the eof character in Scroll.
b. Otherwise, if the command is the ex a command, it shall be set to the line
appended after, if any; otherwise to the first column.
c. Otherwise, if the command is the ex i command, it shall be set to the line
inserted before, if any; otherwise to the first column.
d. Otherwise, if the command is the ex c command, it shall be set to the indentation
of the line replaced.
autoprint, ap
[Default set]
If autoprint is set, the current line shall be written after each ex command that modifies
the contents of the current edit buffer, and after each tag command for which the tag
search pattern was found or tag line number was valid, unless:
1. The command was executed while in open or visual mode.
2. The command was executed as part of a global or v command or @ buffer execution.
3. The command was the form of the read command that reads a file into the edit buffer.
4. The command was the append, change, or insert command.
5. The command was not terminated by a <newline>.
6. The current line shall be written by a flag specified to the command; for example,
delete # shall write the current line as specified for the flag modifier to the delete
command, and not as specified by the autoprint edit option.
autowrite, aw
[Default unset]
If autowrite is set, and the edit buffer has been modified since it was last completely
written to any file, the contents of the edit buffer shall be written as if the ex write
command had been specified without arguments, before each command affected by the
autowrite edit option is executed. Appending the character '!' to the command name of any
of the ex commands except '!' shall prevent the write. If the write fails, it shall be an
error and the command shall not be executed.
beautify, bf
[Default unset]
If beautify is set, all non-printable characters, other than <tab>, <newline>, and <form-
feed> characters, shall be discarded from text read in from files.
directory, dir
[Default implementation-defined]
The value of this option specifies the directory in which the editor buffer is to be
placed. If this directory is not writable by the user, the editor shall quit.
edcompatible, ed
[Default unset]
Causes the presence of g and c suffixes on substitute commands to be remembered, and
toggled by repeating the suffixes.
errorbells, eb
[Default unset]
If the editor is in ex mode, and the terminal does not support a standout mode (such as
inverse video), and errorbells is set, error messages shall be preceded by alerting the
terminal.
exrc
[Default unset]
If exrc is set, ex shall access any .exrc file in the current directory, as described in
Initialization in ex and vi. If exrc is not set, ex shall ignore any .exrc file in the
current directory during initialization, unless the current directory is that named by the
HOME environment variable.
ignorecase, ic
[Default unset]
If ignorecase is set, characters that have uppercase and lowercase representations shall
have those representations considered as equivalent for purposes of regular expression
comparison.
The ignorecase edit option shall affect all remembered regular expressions; for example,
unsetting the ignorecase edit option shall cause a subsequent vi n command to search for
the last basic regular expression in a case-sensitive fashion.
list
[Default unset]
If list is set, edit buffer lines written while in ex command mode shall be written as
specified for the print command with the l flag specified. In open or visual mode, each
edit buffer line shall be displayed as specified for the ex print command with the l flag
specified. In open or visual text input mode, when the cursor does not rest on any
character in the line, it shall rest on the '$' marking the end of the line.
magic
[Default set]
If magic is set, modify the interpretation of characters in regular expressions and
substitution replacement strings (see Regular Expressions in ex and Replacement Strings in
ex).
mesg
[Default set]
If mesg is set, the permission for others to use the write or talk commands to write to
the terminal shall be turned on while in open or visual mode. The shell-level command mesg
n shall take precedence over any setting of the ex mesg option; that is, if mesg y was
issued before the editor started (or in a shell escape), such as:
:!mesg y
the mesg option in ex shall suppress incoming messages, but the mesg option shall not
enable incoming messages if mesg n was issued.
number, nu
[Default unset]
If number is set, edit buffer lines written while in ex command mode shall be written with
line numbers, in the format specified by the print command with the # flag specified. In
ex text input mode, each line shall be preceded by the line number it will have in the
file.
In open or visual mode, each edit buffer line shall be displayed with a preceding line
number, in the format specified by the ex print command with the # flag specified. This
line number shall not be considered part of the line for the purposes of evaluating the
current column; that is, column position 1 shall be the first column position after the
format specified by the print command.
paragraphs, para
[Default in the POSIX locale IPLPPPQPP LIpplpipbp]
The paragraphs edit option shall define additional paragraph boundaries for the open and
visual mode commands. The paragraphs edit option can be set to a character string
consisting of zero or more character pairs. It shall be an error to set it to an odd
number of characters.
prompt
[Default set]
If prompt is set, ex command mode input shall be prompted for with a <colon> (':'); when
unset, no prompt shall be written.
readonly
[Default see text]
If the readonly edit option is set, read-only mode shall be enabled (see Write). The
readonly edit option shall be initialized to set if either of the following conditions are
true:
* The command-line option -R was specified.
* Performing actions equivalent to the access() function called with the following
arguments indicates that the file lacks write permission:
1. The current pathname is used as the path argument.
2. The constant W_OK is used as the amode argument.
The readonly edit option may be initialized to set for other, implementation-defined
reasons. The readonly edit option shall not be initialized to unset based on any special
privileges of the user or process. The readonly edit option shall be reinitialized each
time that the contents of the edit buffer are replaced (for example, by an edit or next
command) unless the user has explicitly set it, in which case it shall remain set until
the user explicitly unsets it. Once unset, it shall again be reinitialized each time that
the contents of the edit buffer are replaced.
redraw
[Default unset]
The editor simulates an intelligent terminal on a dumb terminal. (Since this is likely to
require a large amount of output to the terminal, it is useful only at high transmission
speeds.)
remap
[Default set]
If remap is set, map translation shall allow for maps defined in terms of other maps;
translation shall continue until a final product is obtained. If unset, only a one-step
translation shall be done.
report
[Default 5]
The value of this report edit option specifies what number of lines being added, copied,
deleted, or modified in the edit buffer will cause an informational message to be written
to the user. The following conditions shall cause an informational message. The message
shall contain the number of lines added, copied, deleted, or modified, but is otherwise
unspecified.
* An ex or vi editor command, other than open, undo, or visual, that modifies at least
the value of the report edit option number of lines, and which is not part of an ex
global or v command, or ex or vi buffer execution, shall cause an informational
message to be written.
* An ex yank or vi y or Y command, that copies at least the value of the report edit
option plus 1 number of lines, and which is not part of an ex global or v command, or
ex or vi buffer execution, shall cause an informational message to be written.
* An ex global, v, open, undo, or visual command or ex or vi buffer execution, that adds
or deletes a total of at least the value of the report edit option number of lines,
and which is not part of an ex global or v command, or ex or vi buffer execution,
shall cause an informational message to be written. (For example, if 3 lines were
added and 8 lines deleted during an ex visual command, 5 would be the number compared
against the report edit option after the command completed.)
scroll, scr
[Default (number of lines in the display -1)/2]
The value of the scroll edit option shall determine the number of lines scrolled by the ex
<control>‐D and z commands. For the vi <control>‐D and <control>‐U commands, it shall be
the initial number of lines to scroll when no previous <control>‐D or <control>‐U command
has been executed.
sections
[Default in the POSIX locale NHSHH HUnhsh]
The sections edit option shall define additional section boundaries for the open and
visual mode commands. The sections edit option can be set to a character string consisting
of zero or more character pairs; it shall be an error to set it to an odd number of
characters.
shell, sh
[Default from the environment variable SHELL]
The value of this option shall be a string. The default shall be taken from the SHELL
environment variable. If the SHELL environment variable is null or empty, the sh (see sh)
utility shall be the default.
shiftwidth, sw
[Default 8]
The value of this option shall give the width in columns of an indentation level used
during autoindentation and by the shift commands (< and >).
showmatch, sm
[Default unset]
The functionality described for the showmatch edit option need not be supported on block-
mode terminals or terminals with insufficient capabilities.
If showmatch is set, in open or visual mode, when a ')' or '}' is typed, if the matching
'(' or '{' is currently visible on the display, the matching '(' or '{' shall be flagged
moving the cursor to its location for an unspecified amount of time.
showmode
[Default unset]
If showmode is set, in open or visual mode, the current mode that the editor is in shall
be displayed on the last line of the display. Command mode and text input mode shall be
differentiated; other unspecified modes and implementation-defined information may be
displayed.
slowopen
[Default unset]
If slowopen is set during open and visual text input modes, the editor shall not update
portions of the display other than those display line columns that display the characters
entered by the user (see Input Mode Commands in vi).
tabstop, ts
[Default 8]
The value of this edit option shall specify the column boundary used by a <tab> in the
display (see autoprint, ap and Input Mode Commands in vi).
taglength, tl
[Default zero]
The value of this edit option shall specify the maximum number of characters that are
considered significant in the user-specified tag name and in the tag name from the tags
file. If the value is zero, all characters in both tag names shall be significant.
tags
[Default see text]
The value of this edit option shall be a string of <blank>-delimited pathnames of files
used by the tag command. The default value is unspecified.
term
[Default from the environment variable TERM]
The value of this edit option shall be a string. The default shall be taken from the TERM
variable in the environment. If the TERM environment variable is empty or null, the
default is unspecified. The editor shall use the value of this edit option to determine
the type of the display device.
The results are unspecified if the user changes the value of the term edit option after
editor initialization.
terse
[Default unset]
If terse is set, error messages may be less verbose. However, except for this caveat,
error messages are unspecified. Furthermore, not all error messages need change for
different settings of this option.
warn
[Default set]
If warn is set, and the contents of the edit buffer have been modified since they were
last completely written, the editor shall write a warning message before certain !
commands (see Escape).
window
[Default see text]
A value used in open and visual mode, by the <control>‐B and <control>‐F commands, and, in
visual mode, to specify the number of lines displayed when the screen is repainted.
If the -w command-line option is not specified, the default value shall be set to the
value of the LINES environment variable. If the LINES environment variable is empty or
null, the default shall be the number of lines in the display minus 1.
Setting the window edit option to zero or to a value greater than the number of lines in
the display minus 1 (either explicitly or based on the -w option or the LINES environment
variable) shall cause the window edit option to be set to the number of lines in the
display minus 1.
The baud rate of the terminal line may change the default in an implementation-defined
manner.
wrapmargin, wm
[Default 0]
If the value of this edit option is zero, it shall have no effect.
If not in the POSIX locale, the effect of this edit option is implementation-defined.
Otherwise, it shall specify a number of columns from the ending margin of the terminal.
During open and visual text input modes, for each character for which any part of the
character is displayed in a column that is less than wrapmargin columns from the ending
margin of the display line, the editor shall behave as follows:
1. If the character triggering this event is a <blank>, it, and all immediately preceding
<blank> characters on the current line entered during the execution of the current
text input command, shall be discarded, and the editor shall behave as if the user had
entered a single <newline> instead. In addition, if the next user-entered character is
a <space>, it shall be discarded as well.
2. Otherwise, if there are one or more <blank> characters on the current line immediately
preceding the last group of inserted non-<blank> characters which was entered during
the execution of the current text input command, the <blank> characters shall be
replaced as if the user had entered a single <newline> instead.
If the autoindent edit option is set, and the events described in 1. or 2. are performed,
any <blank> characters at or after the cursor in the current line shall be discarded.
The ending margin shall be determined by the system or overridden by the user, as
described for COLUMNS in the ENVIRONMENT VARIABLES section and the Base Definitions volume
of POSIX.1‐2017, Chapter 8, Environment Variables.
wrapscan, ws
[Default set]
If wrapscan is set, searches (the ex / or ? addresses, or open and visual mode /, ?, N,
and n commands) shall wrap around the beginning or end of the edit buffer; when unset,
searches shall stop at the beginning or end of the edit buffer.
writeany, wa
[Default unset]
If writeany is set, some of the checks performed when executing the ex write commands
shall be inhibited, as described in editor option autowrite.
EXIT STATUS
The following exit values shall be returned:
0 Successful completion.
>0 An error occurred.
CONSEQUENCES OF ERRORS
When any error is encountered and the standard input is not a terminal device file, ex
shall not write the file or return to command or text input mode, and shall terminate with
a non-zero exit status.
Otherwise, when an unrecoverable error is encountered, it shall be equivalent to a SIGHUP
asynchronous event.
Otherwise, when an error is encountered, the editor shall behave as specified in Command
Line Parsing in ex.
The following sections are informative.
APPLICATION USAGE
If a SIGSEGV signal is received while ex is saving a file, the file might not be
successfully saved.
The next command can accept more than one file, so usage such as:
next `ls [abc]*`
is valid; it would not be valid for the edit or read commands, for example, because they
expect only one file and unspecified results occur.
EXAMPLES
None.
RATIONALE
The ex/vi specification is based on the historical practice found in the 4 BSD and System
V implementations of ex and vi.
A restricted editor (both the historical red utility and modifications to ex) were
considered and rejected for inclusion. Neither option provided the level of security that
users might expect.
It is recognized that ex visual mode and related features would be difficult, if not
impossible, to implement satisfactorily on a block-mode terminal, or a terminal without
any form of cursor addressing; thus, it is not a mandatory requirement that such features
should work on all terminals. It is the intention, however, that an ex implementation
should provide the full set of capabilities on all terminals capable of supporting them.
Options
The -c replacement for +command was inspired by the -e option of sed. Historically, all
such commands (see edit and next as well) were executed from the last line of the edit
buffer. This meant, for example, that "+/pattern" would fail unless the wrapscan option
was set. POSIX.1‐2008 requires conformance to historical practice. The +command option is
no longer specified by POSIX.1‐2008 but may be present in some implementations.
Historically, some implementations restricted the ex commands that could be listed as part
of the command line arguments. For consistency, POSIX.1‐2008 does not permit these
restrictions.
In historical implementations of the editor, the -R option (and the readonly edit option)
only prevented overwriting of files; appending to files was still permitted, mapping
loosely into the csh noclobber variable. Some implementations, however, have not followed
this semantic, and readonly does not permit appending either. POSIX.1‐2008 follows the
latter practice, believing that it is a more obvious and intuitive meaning of readonly.
The -s option suppresses all interactive user feedback and is useful for editing scripts
in batch jobs. The list of specific effects is historical practice. The terminal type
``incapable of supporting open and visual modes'' has historically been named ``dumb''.
The -t option was required because the ctags utility appears in POSIX.1‐2008 and the
option is available in all historical implementations of ex.
Historically, the ex and vi utilities accepted a -x option, which did encryption based on
the algorithm found in the historical crypt utility. The -x option for encryption, and the
associated crypt utility, were omitted because the algorithm used was not specifiable and
the export control laws of some nations make it difficult to export cryptographic
technology. In addition, it did not historically provide the level of security that users
might expect.
Standard Input
An end-of-file condition is not equivalent to an end-of-file character. A common end-of-
file character, <control>‐D, is historically an ex command.
There was no maximum line length in historical implementations of ex. Specifically, as it
was parsed in chunks, the addresses had a different maximum length than the filenames.
Further, the maximum line buffer size was declared as BUFSIZ, which was different lengths
on different systems. This version selected the value of {LINE_MAX} to impose a reasonable
restriction on portable usage of ex and to aid test suite writers in their development of
realistic tests that exercise this limit.
Input Files
It was an explicit decision by the standard developers that a <newline> be added to any
file lacking one. It was believed that this feature of ex and vi was relied on by users in
order to make text files lacking a trailing <newline> more portable. It is recognized that
this will require a user-specified option or extension for implementations that permit ex
and vi to edit files of type other than text if such files are not otherwise identified by
the system. It was agreed that the ability to edit files of arbitrary type can be useful,
but it was not considered necessary to mandate that an ex or vi implementation be required
to handle files other than text files.
The paragraph in the INPUT FILES section, ``By default, ...'', is intended to close a
long-standing security problem in ex and vi; that of the ``modeline'' or ``modelines''
edit option. This feature allows any line in the first or last five lines of the file
containing the strings "ex:" or "vi:" (and, apparently, "ei:" or "vx:") to be a line
containing editor commands, and ex interprets all the text up to the next ':' or <newline>
as a command. Consider the consequences, for example, of an unsuspecting user using ex or
vi as the editor when replying to a mail message in which a line such as:
ex:! rm -rf :
appeared in the signature lines. The standard developers believed strongly that an editor
should not by default interpret any lines of a file. Vendors are strongly urged to delete
this feature from their implementations of ex and vi.
Asynchronous Events
The intention of the phrase ``complete write'' is that the entire edit buffer be written
to stable storage. The note regarding temporary files is intended for implementations that
use temporary files to back edit buffers unnamed by the user.
Historically, SIGQUIT was ignored by ex, but was the equivalent of the Q command in visual
mode; that is, it exited visual mode and entered ex mode. POSIX.1‐2008 permits, but does
not require, this behavior. Historically, SIGINT was often used by vi users to terminate
text input mode (<control>‐C is often easier to enter than <ESC>). Some implementations
of vi alerted the terminal on this event, and some did not. POSIX.1‐2008 requires that
SIGINT behave identically to <ESC>, and that the terminal not be alerted.
Historically, suspending the ex editor during text input mode was similar to SIGINT, as
completed lines were retained, but any partial line discarded, and the editor returned to
command mode. POSIX.1‐2008 is silent on this issue; implementations are encouraged to
follow historical practice, where possible.
Historically, the vi editor did not treat SIGTSTP as an asynchronous event, and it was
therefore impossible to suspend the editor in visual text input mode. There are two major
reasons for this. The first is that SIGTSTP is a broadcast signal on UNIX systems, and the
chain of events where the shell execs an application that then execs vi usually caused
confusion for the terminal state if SIGTSTP was delivered to the process group in the
default manner. The second was that most implementations of the UNIX curses package did
not handle SIGTSTP safely, and the receipt of SIGTSTP at the wrong time would cause them
to crash. POSIX.1‐2008 is silent on this issue; implementations are encouraged to treat
suspension as an asynchronous event if possible.
Historically, modifications to the edit buffer made before SIGINT interrupted an operation
were retained; that is, anywhere from zero to all of the lines to be modified might have
been modified by the time the SIGINT arrived. These changes were not discarded by the
arrival of SIGINT. POSIX.1‐2008 permits this behavior, noting that the undo command is
required to be able to undo these partially completed commands.
The action taken for signals other than SIGINT, SIGCONT, SIGHUP, and SIGTERM is
unspecified because some implementations attempt to save the edit buffer in a useful state
when other signals are received.
Standard Error
For ex/vi, diagnostic messages are those messages reported as a result of a failed attempt
to invoke ex or vi, such as invalid options or insufficient resources, or an abnormal
termination condition. Diagnostic messages should not be confused with the error messages
generated by inappropriate or illegal user commands.
Initialization in ex and vi
If an ex command (other than cd, chdir, or source) has a filename argument, one or both of
the alternate and current pathnames will be set. Informally, they are set as follows:
1. If the ex command is one that replaces the contents of the edit buffer, and it
succeeds, the current pathname will be set to the filename argument (the first
filename argument in the case of the next command) and the alternate pathname will be
set to the previous current pathname, if there was one.
2. In the case of the file read/write forms of the read and write commands, if there is
no current pathname, the current pathname will be set to the filename argument.
3. Otherwise, the alternate pathname will be set to the filename argument.
For example, :edit foo and :recover foo, when successful, set the current pathname, and,
if there was a previous current pathname, the alternate pathname. The commands :write,
!command, and :edit set neither the current or alternate pathnames. If the :edit foo
command were to fail for some reason, the alternate pathname would be set. The read and
write commands set the alternate pathname to their file argument, unless the current
pathname is not set, in which case they set the current pathname to their file arguments.
The alternate pathname was not historically set by the :source command. POSIX.1‐2008
requires conformance to historical practice. Implementations adding commands that take
filenames as arguments are encouraged to set the alternate pathname as described here.
Historically, ex and vi read the .exrc file in the $HOME directory twice, if the editor
was executed in the $HOME directory. POSIX.1‐2008 prohibits this behavior.
Historically, the 4 BSD ex and vi read the $HOME and local .exrc files if they were owned
by the real ID of the user, or the sourceany option was set, regardless of other
considerations. This was a security problem because it is possible to put normal UNIX
system commands inside a .exrc file. POSIX.1‐2008 does not specify the sourceany option,
and historical implementations are encouraged to delete it.
The .exrc files must be owned by the real ID of the user, and not writable by anyone other
than the owner. The appropriate privileges exception is intended to permit users to
acquire special privileges, but continue to use the .exrc files in their home directories.
System V Release 3.2 and later vi implementations added the option [no]exrc. The behavior
is that local .exrc files are read-only if the exrc option is set. The default for the
exrc option was off, so by default, local .exrc files were not read. The problem this was
intended to solve was that System V permitted users to give away files, so there is no
possible ownership or writeability test to ensure that the file is safe. This is still a
security problem on systems where users can give away files, but there is nothing
additional that POSIX.1‐2008 can do. The implementation-defined exception is intended to
permit groups to have local .exrc files that are shared by users, by creating pseudo-users
to own the shared files.
POSIX.1‐2008 does not mention system-wide ex and vi start-up files. While they exist in
several implementations of ex and vi, they are not present in any implementations
considered historical practice by POSIX.1‐2008. Implementations that have such files
should use them only if they are owned by the real user ID or an appropriate user (for
example, root on UNIX systems) and if they are not writable by any user other than their
owner. System-wide start-up files should be read before the EXINIT variable, $HOME/.exrc,
or local .exrc files are evaluated.
Historically, any ex command could be entered in the EXINIT variable or the .exrc file,
although ones requiring that the edit buffer already contain lines of text generally
caused historical implementations of the editor to drop core. POSIX.1‐2008 requires that
any ex command be permitted in the EXINIT variable and .exrc files, for simplicity of
specification and consistency, although many of them will obviously fail under many
circumstances.
The initialization of the contents of the edit buffer uses the phrase ``the effect shall
be'' with regard to various ex commands. The intent of this phrase is that edit buffer
contents loaded during the initialization phase not be lost; that is, loading the edit
buffer should fail if the .exrc file read in the contents of a file and did not
subsequently write the edit buffer. An additional intent of this phrase is to specify that
the initial current line and column is set as specified for the individual ex commands.
Historically, the -t option behaved as if the tag search were a +command; that is, it was
executed from the last line of the file specified by the tag. This resulted in the search
failing if the pattern was a forward search pattern and the wrapscan edit option was not
set. POSIX.1‐2008 does not permit this behavior, requiring that the search for the tag
pattern be performed on the entire file, and, if not found, that the current line be set
to a more reasonable location in the file.
Historically, the empty edit buffer presented for editing when a file was not specified by
the user was unnamed. This is permitted by POSIX.1‐2008; however, implementations are
encouraged to provide users a temporary filename for this buffer because it permits them
the use of ex commands that use the current pathname during temporary edit sessions.
Historically, the file specified using the -t option was not part of the current argument
list. This practice is permitted by POSIX.1‐2008; however, implementations are encouraged
to include its name in the current argument list for consistency.
Historically, the -c command was generally not executed until a file that already exists
was edited. POSIX.1‐2008 requires conformance to this historical practice. Commands that
could cause the -c command to be executed include the ex commands edit, next, recover,
rewind, and tag, and the vi commands <control>‐^ and <control>‐]. Historically, reading a
file into an edit buffer did not cause the -c command to be executed (even though it might
set the current pathname) with the exception that it did cause the -c command to be
executed if: the editor was in ex mode, the edit buffer had no current pathname, the edit
buffer was empty, and no read commands had yet been attempted. For consistency and
simplicity of specification, POSIX.1‐2008 does not permit this behavior.
Historically, the -r option was the same as a normal edit session if there was no recovery
information available for the file. This allowed users to enter:
vi -r *.c
and recover whatever files were recoverable. In some implementations, recovery was
attempted only on the first file named, and the file was not entered into the argument
list; in others, recovery was attempted for each file named. In addition, some historical
implementations ignored -r if -t was specified or did not support command line file
arguments with the -t option. For consistency and simplicity of specification,
POSIX.1‐2008 disallows these special cases, and requires that recovery be attempted the
first time each file is edited.
Historically, vi initialized the ` and ' marks, but ex did not. This meant that if the
first command in ex mode was visual or if an ex command was executed first (for example,
vi +10 file), vi was entered without the marks being initialized. Because the standard
developers believed the marks to be generally useful, and for consistency and simplicity
of specification, POSIX.1‐2008 requires that they always be initialized if in open or
visual mode, or if in ex mode and the edit buffer is not empty. Not initializing it in ex
mode if the edit buffer is empty is historical practice; however, it has always been
possible to set (and use) marks in empty edit buffers in open and visual mode edit
sessions.
Addressing
Historically, ex and vi accepted the additional addressing forms '\/' and '\?'. They were
equivalent to "//" and "??", respectively. They are not required by POSIX.1‐2008, mostly
because nobody can remember whether they ever did anything different historically.
Historically, ex and vi permitted an address of zero for several commands, and permitted
the % address in empty files for others. For consistency, POSIX.1‐2008 requires support
for the former in the few commands where it makes sense, and disallows it otherwise. In
addition, because POSIX.1‐2008 requires that % be logically equivalent to "1,$", it is
also supported where it makes sense and disallowed otherwise.
Historically, the % address could not be followed by further addresses. For consistency
and simplicity of specification, POSIX.1‐2008 requires that additional addresses be
supported.
All of the following are valid addresses:
+++ Three lines after the current line.
/re/- One line before the next occurrence of re.
-2 Two lines before the current line.
3 ---- 2 Line one (note intermediate negative address).
1 2 3 Line six.
Any number of addresses can be provided to commands taking addresses; for example,
"1,2,3,4,5p" prints lines 4 and 5, because two is the greatest valid number of addresses
accepted by the print command. This, in combination with the <semicolon> delimiter,
permits users to create commands based on ordered patterns in the file. For example, the
command 3;/foo/;+2print will display the first line after line 3 that contains the pattern
foo, plus the next two lines. Note that the address 3; must be evaluated before being
discarded because the search origin for the /foo/ command depends on this.
Historically, values could be added to addresses by including them after one or more
<blank> characters; for example, 3 - 5p wrote the seventh line of the file, and /foo/ 5
was the same as /foo/+5. However, only absolute values could be added; for example,
5 /foo/ was an error. POSIX.1‐2008 requires conformance to historical practice. Address
offsets are separately specified from addresses because they could historically be
provided to visual mode search commands.
Historically, any missing addresses defaulted to the current line. This was true for
leading and trailing <comma>-delimited addresses, and for trailing <semicolon>-delimited
addresses. For consistency, POSIX.1‐2008 requires it for leading <semicolon> addresses as
well.
Historically, ex and vi accepted the '^' character as both an address and as a flag offset
for commands. In both cases it was identical to the '-' character. POSIX.1‐2008 does not
require or prohibit this behavior.
Historically, the enhancements to basic regular expressions could be used in addressing;
for example, '~', '\<', and '\>'. POSIX.1‐2008 requires conformance to historical
practice; that is, that regular expression usage be consistent, and that regular
expression enhancements be supported wherever regular expressions are used.
Command Line Parsing in ex
Historical ex command parsing was even more complex than that described here. POSIX.1‐2008
requires the subset of the command parsing that the standard developers believed was
documented and that users could reasonably be expected to use in a portable fashion, and
that was historically consistent between implementations. (The discarded functionality is
obscure, at best.) Historical implementations will require changes in order to comply
with POSIX.1‐2008; however, users are not expected to notice any of these changes. Most
of the complexity in ex parsing is to handle three special termination cases:
1. The !, global, v, and the filter versions of the read and write commands are delimited
by <newline> characters (they can contain <vertical-line> characters that are usually
shell pipes).
2. The ex, edit, next, and visual in open and visual mode commands all take ex commands,
optionally containing <vertical-line> characters, as their first arguments.
3. The s command takes a regular expression as its first argument, and uses the
delimiting characters to delimit the command.
Historically, <vertical-line> characters in the +command argument of the ex, edit, next,
vi, and visual commands, and in the pattern and replacement parts of the s command, did
not delimit the command, and in the filter cases for read and write, and the !, global,
and v commands, they did not delimit the command at all. For example, the following
commands are all valid:
:edit +25 | s/abc/ABC/ file.c
:s/ | /PIPE/
:read !spell % | columnate
:global/pattern/p | l
:s/a/b/ | s/c/d | set
Historically, empty or <blank> filled lines in .exrc files and sourced files (as well as
EXINIT variables and ex command scripts) were treated as default commands; that is, print
commands. POSIX.1‐2008 specifically requires that they be ignored when encountered in
.exrc and sourced files to eliminate a common source of new user error.
Historically, ex commands with multiple adjacent (or <blank>-separated) vertical lines
were handled oddly when executed from ex mode. For example, the command ||| <carriage-
return>, when the cursor was on line 1, displayed lines 2, 3, and 5 of the file. In
addition, the command | would only display the line after the next line, instead of the
next two lines. The former worked more logically when executed from vi mode, and displayed
lines 2, 3, and 4. POSIX.1‐2008 requires the vi behavior; that is, a single default
command and line number increment for each command separator, and trailing <newline>
characters after <vertical-line> separators are discarded.
Historically, ex permitted a single extra <colon> as a leading command character; for
example, :g/pattern/:p was a valid command. POSIX.1‐2008 generalizes this to require that
any number of leading <colon> characters be stripped.
Historically, any prefix of the delete command could be followed without intervening
<blank> characters by a flag character because in the command d p, p is interpreted as the
buffer p. POSIX.1‐2008 requires conformance to historical practice.
Historically, the k command could be followed by the mark name without intervening <blank>
characters. POSIX.1‐2008 requires conformance to historical practice.
Historically, the s command could be immediately followed by flag and option characters;
for example, s/e/E/|s|sgc3p was a valid command. However, flag characters could not stand
alone; for example, the commands sp and s l would fail, while the command sgp and s gl
would succeed. (Obviously, the '#' flag character was used as a delimiter character if it
followed the command.) Another issue was that option characters had to precede flag
characters even when the command was fully specified; for example, the command s/e/E/pg
would fail, while the command s/e/E/gp would succeed. POSIX.1‐2008 requires conformance to
historical practice.
Historically, the first command name that had a prefix matching the input from the user
was the executed command; for example, ve, ver, and vers all executed the version command.
Commands were in a specific order, however, so that a matched append, not abbreviate.
POSIX.1‐2008 requires conformance to historical practice. The restriction on command
search order for implementations with extensions is to avoid the addition of commands such
that the historical prefixes would fail to work portably.
Historical implementations of ex and vi did not correctly handle multiple ex commands,
separated by <vertical-line> characters, that entered or exited visual mode or the editor.
Because implementations of vi exist that do not exhibit this failure mode, POSIX.1‐2008
does not permit it.
The requirement that alphabetic command names consist of all following alphabetic
characters up to the next non-alphabetic character means that alphabetic command names
must be separated from their arguments by one or more non-alphabetic characters, normally
a <blank> or '!' character, except as specified for the exceptions, the delete, k, and s
commands.
Historically, the repeated execution of the ex default print commands (<control>‐D, eof,
<newline>, <carriage-return>) erased any prompting character and displayed the next lines
without scrolling the terminal; that is, immediately below any previously displayed lines.
This provided a cleaner presentation of the lines in the file for the user. POSIX.1‐2008
does not require this behavior because it may be impossible in some situations; however,
implementations are strongly encouraged to provide this semantic if possible.
Historically, it was possible to change files in the middle of a command, and have the
rest of the command executed in the new file; for example:
:edit +25 file.c | s/abc/ABC/ | 1
was a valid command, and the substitution was attempted in the newly edited file.
POSIX.1‐2008 requires conformance to historical practice. The following commands are
examples that exercise the ex parser:
echo 'foo | bar' > file1; echo 'foo/bar' > file2;
vi
:edit +1 | s/|/PIPE/ | w file1 | e file2 | 1 | s/\//SLASH/ | wq
Historically, there was no protection in editor implementations to avoid ex global, v, @,
or * commands changing edit buffers during execution of their associated commands. Because
this would almost invariably result in catastrophic failure of the editor, and
implementations exist that do exhibit these problems, POSIX.1‐2008 requires that changing
the edit buffer during a global or v command, or during a @ or * command for which there
will be more than a single execution, be an error. Implementations supporting multiple
edit buffers simultaneously are strongly encouraged to apply the same semantics to
switching between buffers as well.
The ex command quoting required by POSIX.1‐2008 is a superset of the quoting in historical
implementations of the editor. For example, it was not historically possible to escape a
<blank> in a filename; for example, :edit foo\\\ bar would report that too many filenames
had been entered for the edit command, and there was no method of escaping a <blank> in
the first argument of an edit, ex, next, or visual command at all. POSIX.1‐2008 extends
historical practice, requiring that quoting behavior be made consistent across all ex
commands, except for the map, unmap, abbreviate, and unabbreviate commands, which
historically used <control>‐V instead of <backslash> characters for quoting. For those
four commands, POSIX.1‐2008 requires conformance to historical practice.
Backslash quoting in ex is non-intuitive. <backslash>-escapes are ignored unless they
escape a special character; for example, when performing file argument expansion, the
string "\\%" is equivalent to '\%', not "\<current pathname>". This can be confusing for
users because <backslash> is usually one of the characters that causes shell expansion to
be performed, and therefore shell quoting rules must be taken into consideration.
Generally, quoting characters are only considered if they escape a special character, and
a quoting character must be provided for each layer of parsing for which the character is
special. As another example, only a single <backslash> is necessary for the '\l' sequence
in substitute replacement patterns, because the character 'l' is not special to any
parsing layer above it.
<control>‐V quoting in ex is slightly different from backslash quoting. In the four
commands where <control>‐V quoting applies (abbreviate, unabbreviate, map, and unmap), any
character may be escaped by a <control>‐V whether it would have a special meaning or not.
POSIX.1‐2008 requires conformance to historical practice.
Historical implementations of the editor did not require delimiters within character
classes to be escaped; for example, the command :s/[/]// on the string "xxx/yyy" would
delete the '/' from the string. POSIX.1‐2008 disallows this historical practice for
consistency and because it places a large burden on implementations by requiring that
knowledge of regular expressions be built into the editor parser.
Historically, quoting <newline> characters in ex commands was handled inconsistently. In
most cases, the <newline> character always terminated the command, regardless of any
preceding escape character, because <backslash> characters did not escape <newline>
characters for most ex commands. However, some ex commands (for example, s, map, and
abbreviation) permitted <newline> characters to be escaped (although in the case of map
and abbreviation, <control>‐V characters escaped them instead of <backslash> characters).
This was true in not only the command line, but also .exrc and sourced files. For example,
the command:
map = foo<control-V><newline>bar
would succeed, although it was sometimes difficult to get the <control>‐V and the inserted
<newline> passed to the ex parser. For consistency and simplicity of specification,
POSIX.1‐2008 requires that it be possible to escape <newline> characters in ex commands at
all times, using <backslash> characters for most ex commands, and using <control>‐V
characters for the map and abbreviation commands. For example, the command
print<newline>list is required to be parsed as the single command print<newline>list.
While this differs from historical practice, POSIX.1‐2008 developers believed it unlikely
that any script or user depended on the historical behavior.
Historically, an error in a command specified using the -c option did not cause the rest
of the -c commands to be discarded. POSIX.1‐2008 disallows this for consistency with
mapped keys, the @, global, source, and v commands, the EXINIT environment variable, and
the .exrc files.
Input Editing in ex
One of the common uses of the historical ex editor is over slow network connections.
Editors that run in canonical mode can require far less traffic to and from, and far less
processing on, the host machine, as well as more easily supporting block-mode terminals.
For these reasons, POSIX.1‐2008 requires that ex be implemented using canonical mode input
processing, as was done historically.
POSIX.1‐2008 does not require the historical 4 BSD input editing characters ``word erase''
or ``literal next''. For this reason, it is unspecified how they are handled by ex,
although they must have the required effect. Implementations that resolve them after the
line has been ended using a <newline> or <control>‐M character, and implementations that
rely on the underlying system terminal support for this processing, are both conforming.
Implementations are strongly urged to use the underlying system functionality, if at all
possible, for compatibility with other system text input interfaces.
Historically, when the eof character was used to decrement the autoindent level, the
cursor moved to display the new end of the autoindent characters, but did not move the
cursor to a new line, nor did it erase the <control>‐D character from the line.
POSIX.1‐2008 does not specify that the cursor remain on the same line or that the rest of
the line is erased; however, implementations are strongly encouraged to provide the best
possible user interface; that is, the cursor should remain on the same line, and any
<control>‐D character on the line should be erased.
POSIX.1‐2008 does not require the historical 4 BSD input editing character ``reprint'',
traditionally <control>‐R, which redisplayed the current input from the user. For this
reason, and because the functionality cannot be implemented after the line has been
terminated by the user, POSIX.1‐2008 makes no requirements about this functionality.
Implementations are strongly urged to make this historical functionality available, if
possible.
Historically, <control>‐Q did not perform a literal next function in ex, as it did in vi.
POSIX.1‐2008 requires conformance to historical practice to avoid breaking historical ex
scripts and .exrc files.
eof
Whether the eof character immediately modifies the autoindent characters in the prompt is
left unspecified so that implementations can conform in the presence of systems that do
not support this functionality. Implementations are encouraged to modify the line and
redisplay it immediately, if possible.
The specification of the handling of the eof character differs from historical practice
only in that eof characters are not discarded if they follow normal characters in the text
input. Historically, they were always discarded.
Command Descriptions in ex
Historically, several commands (for example, global, v, visual, s, write, wq, yank, !, <,
>, &, and ~) were executable in empty files (that is, the default address(es) were 0), or
permitted explicit addresses of 0 (for example, 0 was a valid address, or 0,0 was a valid
range). Addresses of 0, or command execution in an empty file, make sense only for
commands that add new text to the edit buffer or write commands (because users may wish to
write empty files). POSIX.1‐2008 requires this behavior for such commands and disallows it
otherwise, for consistency and simplicity of specification.
A count to an ex command has been historically corrected to be no greater than the last
line in a file; for example, in a five-line file, the command 1,6print would fail, but the
command 1print300 would succeed. POSIX.1‐2008 requires conformance to historical practice.
Historically, the use of flags in ex commands could be obscure. General historical
practice was as described by POSIX.1‐2008, but there were some special cases. For
instance, the list, number, and print commands ignored trailing address offsets; for
example, 3p +++# would display line 3, and 3 would be the current line after the execution
of the command. The open and visual commands ignored both the trailing offsets and the
trailing flags. Also, flags specified to the open and visual commands interacted badly
with the list edit option, and setting and then unsetting it during the open/visual
session would cause vi to stop displaying lines in the specified format. For consistency
and simplicity of specification, POSIX.1‐2008 does not permit any of these exceptions to
the general rule.
POSIX.1‐2008 uses the word copy in several places when discussing buffers. This is not
intended to imply implementation.
Historically, ex users could not specify numeric buffers because of the ambiguity this
would cause; for example, in the command 3 delete 2, it is unclear whether 2 is a buffer
name or a count. POSIX.1‐2008 requires conformance to historical practice by default, but
does not preclude extensions.
Historically, the contents of the unnamed buffer were frequently discarded after commands
that did not explicitly affect it; for example, when using the edit command to switch
files. For consistency and simplicity of specification, POSIX.1‐2008 does not permit this
behavior.
The ex utility did not historically have access to the numeric buffers, and, furthermore,
deleting lines in ex did not modify their contents. For example, if, after doing a delete
in vi, the user switched to ex, did another delete, and then switched back to vi, the
contents of the numeric buffers would not have changed. POSIX.1‐2008 requires conformance
to historical practice. Numeric buffers are described in the ex utility in order to
confine the description of buffers to a single location in POSIX.1‐2008.
The metacharacters that trigger shell expansion in file arguments match historical
practice, as does the method for doing shell expansion. Implementations wishing to provide
users with the flexibility to alter the set of metacharacters are encouraged to provide a
shellmeta string edit option.
Historically, ex commands executed from vi refreshed the screen when it did not strictly
need to do so; for example, :!date > /dev/null does not require a screen refresh because
the output of the UNIX date command requires only a single line of the screen.
POSIX.1‐2008 requires that the screen be refreshed if it has been overwritten, but makes
no requirements as to how an implementation should make that determination.
Implementations may prompt and refresh the screen regardless.
Abbreviate
Historical practice was that characters that were entered as part of an abbreviation
replacement were subject to map expansions, the showmatch edit option, further
abbreviation expansions, and so on; that is, they were logically pushed onto the terminal
input queue, and were not a simple replacement. POSIX.1‐2008 requires conformance to
historical practice. Historical practice was that whenever a non-word character (that had
not been escaped by a <control>‐V) was entered after a word character, vi would check for
abbreviations. The check was based on the type of the character entered before the word
character of the word/non-word pair that triggered the check. The word character of the
word/non-word pair that triggered the check and all characters entered before the trigger
pair that were of that type were included in the check, with the exception of <blank>
characters, which always delimited the abbreviation.
This means that, for the abbreviation to work, the lhs must end with a word character,
there can be no transitions from word to non-word characters (or vice versa) other than
between the last and next-to-last characters in the lhs, and there can be no <blank>
characters in the lhs. In addition, because of the historical quoting rules, it was
impossible to enter a literal <control>‐V in the lhs. POSIX.1‐2008 requires conformance
to historical practice. Historical implementations did not inform users when abbreviations
that could never be used were entered; implementations are strongly encouraged to do so.
For example, the following abbreviations will work:
:ab (p REPLACE
:ab p REPLACE
:ab ((p REPLACE
The following abbreviations will not work:
:ab ( REPLACE
:ab (pp REPLACE
Historical practice is that words on the vi colon command line were subject to
abbreviation expansion, including the arguments to the abbrev (and more interestingly) the
unabbrev command. Because there are implementations that do not do abbreviation expansion
for the first argument to those commands, this is permitted, but not required, by
POSIX.1‐2008. However, the following sequence:
:ab foo bar
:ab foo baz
resulted in the addition of an abbreviation of "baz" for the string "bar" in historical
ex/vi, and the sequence:
:ab foo1 bar
:ab foo2 bar
:unabbreviate foo2
deleted the abbreviation "foo1", not "foo2". These behaviors are not permitted by
POSIX.1‐2008 because they clearly violate the expectations of the user.
It was historical practice that <control>‐V, not <backslash>, characters be interpreted as
escaping subsequent characters in the abbreviate command. POSIX.1‐2008 requires
conformance to historical practice; however, it should be noted that an abbreviation
containing a <blank> will never work.
Append
Historically, any text following a <vertical-line> command separator after an append,
change, or insert command became part of the insert text. For example, in the command:
:g/pattern/append|stuff1
a line containing the text "stuff1" would be appended to each line matching pattern. It
was also historically valid to enter:
:append|stuff1
stuff2
.
and the text on the ex command line would be appended along with the text inserted after
it. There was an historical bug, however, that the user had to enter two terminating
lines (the '.' lines) to terminate text input mode in this case. POSIX.1‐2008 requires
conformance to historical practice, but disallows the historical need for multiple
terminating lines.
Change
See the RATIONALE for the append command. Historical practice for cursor positioning after
the change command when no text is input, is as described in POSIX.1‐2008. However, one
System V implementation is known to have been modified such that the cursor is positioned
on the first address specified, and not on the line before the first address. POSIX.1‐2008
disallows this modification for consistency.
Historically, the change command did not support buffer arguments, although some
implementations allow the specification of an optional buffer. This behavior is neither
required nor disallowed by POSIX.1‐2008.
Change Directory
A common extension in ex implementations is to use the elements of a cdpath edit option as
prefix directories for path arguments to chdir that are relative pathnames and that do not
have '.' or ".." as their first component. Elements in the cdpath edit option are
<colon>-separated. The initial value of the cdpath edit option is the value of the shell
CDPATH environment variable. This feature was not included in POSIX.1‐2008 because it does
not exist in any of the implementations considered historical practice.
Copy
Historical implementations of ex permitted copies to lines inside of the specified range;
for example, :2,5copy3 was a valid command. POSIX.1‐2008 requires conformance to
historical practice.
Delete
POSIX.1‐2008 requires support for the historical parsing of a delete command followed by
flags, without any intervening <blank> characters. For example:
1dp Deletes the first line and prints the line that was second.
1delep As for 1dp.
1d Deletes the first line, saving it in buffer p.
1d p1l (Pee-one-ell.) Deletes the first line, saving it in buffer p, and listing the line
that was second.
Edit
Historically, any ex command could be entered as a +command argument to the edit command,
although some (for example, insert and append) were known to confuse historical
implementations. For consistency and simplicity of specification, POSIX.1‐2008 requires
that any command be supported as an argument to the edit command.
Historically, the command argument was executed with the current line set to the last line
of the file, regardless of whether the edit command was executed from visual mode or not.
POSIX.1‐2008 requires conformance to historical practice.
Historically, the +command specified to the edit and next commands was delimited by the
first <blank>, and there was no way to quote them. For consistency, POSIX.1‐2008 requires
that the usual ex backslash quoting be provided.
Historically, specifying the +command argument to the edit command required a filename to
be specified as well; for example, :edit +100 would always fail. For consistency and
simplicity of specification, POSIX.1‐2008 does not permit this usage to fail for that
reason.
Historically, only the cursor position of the last file edited was remembered by the
editor. POSIX.1‐2008 requires that this be supported; however, implementations are
permitted to remember and restore the cursor position for any file previously edited.
File
Historical versions of the ex editor file command displayed a current line and number of
lines in the edit buffer of 0 when the file was empty, while the vi <control>‐G command
displayed a current line and number of lines in the edit buffer of 1 in the same
situation. POSIX.1‐2008 does not permit this discrepancy, instead requiring that a message
be displayed indicating that the file is empty.
Global
The two-pass operation of the global and v commands is not intended to imply
implementation, only the required result of the operation.
The current line and column are set as specified for the individual ex commands. This
requirement is cumulative; that is, the current line and column must track across all the
commands executed by the global or v commands.
Insert
See the RATIONALE for the append command.
Historically, insert could not be used with an address of zero; that is, not when the edit
buffer was empty. POSIX.1‐2008 requires that this command behave consistently with the
append command.
Join
The action of the join command in relation to the special characters is only defined for
the POSIX locale because the correct amount of white space after a period varies; in
Japanese none is required, in French only a single space, and so on.
List
The historical output of the list command was potentially ambiguous. The standard
developers believed correcting this to be more important than adhering to historical
practice, and POSIX.1‐2008 requires unambiguous output.
Map
Historically, command mode maps only applied to command names; for example, if the
character 'x' was mapped to 'y', the command fx searched for the 'x' character, not the
'y' character. POSIX.1‐2008 requires this behavior. Historically, entering <control>‐V as
the first character of a vi command was an error. Several implementations have extended
the semantics of vi such that <control>‐V means that the subsequent command character is
not mapped. This is permitted, but not required, by POSIX.1‐2008. Regardless, using
<control>‐V to escape the second or later character in a sequence of characters that might
match a map command, or any character in text input mode, is historical practice, and
stops the entered keys from matching a map. POSIX.1‐2008 requires conformance to
historical practice.
Historical implementations permitted digits to be used as a map command lhs, but then
ignored the map. POSIX.1‐2008 requires that the mapped digits not be ignored.
The historical implementation of the map command did not permit map commands that were
more than a single character in length if the first character was printable. This behavior
is permitted, but not required, by POSIX.1‐2008.
Historically, mapped characters were remapped unless the remap edit option was not set, or
the prefix of the mapped characters matched the mapping characters; for example, in the
map:
:map ab abcd
the characters "ab" were used as is and were not remapped, but the characters "cd" were
mapped if appropriate. This can cause infinite loops in the vi mapping mechanisms.
POSIX.1‐2008 requires conformance to historical practice, and that such loops be
interruptible.
Text input maps had the same problems with expanding the lhs for the ex map! and unmap!
command as did the ex abbreviate and unabbreviate commands. See the RATIONALE for the ex
abbreviate command. POSIX.1‐2008 requires similar modification of some historical practice
for the map and unmap commands, as described for the abbreviate and unabbreviate commands.
Historically, maps that were subsets of other maps behaved differently depending on the
order in which they were defined. For example:
:map! ab short
:map! abc long
would always translate the characters "ab" to "short", regardless of how fast the
characters "abc" were entered. If the entry order was reversed:
:map! abc long
:map! ab short
the characters "ab" would cause the editor to pause, waiting for the completing 'c'
character, and the characters might never be mapped to "short". For consistency and
simplicity of specification, POSIX.1‐2008 requires that the shortest match be used at all
times.
The length of time the editor spends waiting for the characters to complete the lhs is
unspecified because the timing capabilities of systems are often inexact and variable, and
it may depend on other factors such as the speed of the connection. The time should be
long enough for the user to be able to complete the sequence, but not long enough for the
user to have to wait. Some implementations of vi have added a keytime option, which
permits users to set the number of 0,1 seconds the editor waits for the completing
characters. Because mapped terminal function and cursor keys tend to start with an <ESC>
character, and <ESC> is the key ending vi text input mode, maps starting with <ESC>
characters are generally exempted from this timeout period, or, at least timed out
differently.
Mark
Historically, users were able to set the ``previous context'' marks explicitly. In
addition, the ex commands '' and '` and the vi commands '', ``, `', and '` all referred to
the same mark. In addition, the previous context marks were not set if the command, with
which the address setting the mark was associated, failed. POSIX.1‐2008 requires
conformance to historical practice. Historically, if marked lines were deleted, the mark
was also deleted, but would reappear if the change was undone. POSIX.1‐2008 requires
conformance to historical practice.
The description of the special events that set the ` and ' marks matches historical
practice. For example, historically the command /a/,/b/ did not set the ` and ' marks, but
the command /a/,/b/delete did.
Next
Historically, any ex command could be entered as a +command argument to the next command,
although some (for example, insert and append) were known to confuse historical
implementations. POSIX.1‐2008 requires that any command be permitted and that it behave as
specified. The next command can accept more than one file, so usage such as:
next `ls [abc] `
is valid; it need not be valid for the edit or read commands, for example, because they
expect only one filename.
Historically, the next command behaved differently from the :rewind command in that it
ignored the force flag if the autowrite flag was set. For consistency, POSIX.1‐2008 does
not permit this behavior.
Historically, the next command positioned the cursor as if the file had never been edited
before, regardless. POSIX.1‐2008 does not permit this behavior, for consistency with the
edit command.
Implementations wanting to provide a counterpart to the next command that edited the
previous file have used the command prev[ious], which takes no file argument. POSIX.1‐2008
does not require this command.
Open
Historically, the open command would fail if the open edit option was not set.
POSIX.1‐2008 does not mention the open edit option and does not require this behavior.
Some historical implementations do not permit entering open mode from open or visual mode,
only from ex mode. For consistency, POSIX.1‐2008 does not permit this behavior.
Historically, entering open mode from the command line (that is, vi +open) resulted in
anomalous behaviors; for example, the ex file and set commands, and the vi command
<control>‐G did not work. For consistency, POSIX.1‐2008 does not permit this behavior.
Historically, the open command only permitted '/' characters to be used as the search
pattern delimiter. For consistency, POSIX.1‐2008 requires that the search delimiters used
by the s, global, and v commands be accepted as well.
Preserve
The preserve command does not historically cause the file to be considered unmodified for
the purposes of future commands that may exit the editor. POSIX.1‐2008 requires
conformance to historical practice.
Historical documentation stated that mail was not sent to the user when preserve was
executed; however, historical implementations did send mail in this case. POSIX.1‐2008
requires conformance to the historical implementations.
Print
The writing of NUL by the print command is not specified as a special case because the
standard developers did not want to require ex to support NUL characters. Historically,
characters were displayed using the ARPA standard mappings, which are as follows:
1. Printable characters are left alone.
2. Control characters less than \177 are represented as '^' followed by the character
offset from the '@' character in the ASCII map; for example, \007 is represented as
'^G'.
3. \177 is represented as '^' followed by '?'.
The display of characters having their eighth bit set was less standard. Existing
implementations use hex (0x00), octal (\000), and a meta-bit display. (The latter
displayed bytes that had their eighth bit set as the two characters "M-" followed by the
seven-bit display as described above.) The latter probably has the best claim to
historical practice because it was used for the -v option of 4 BSD and 4 BSD-derived
versions of the cat utility since 1980.
No specific display format is required by POSIX.1‐2008.
Explicit dependence on the ASCII character set has been avoided where possible, hence the
use of the phrase an ``implementation-defined multi-character sequence'' for the display
of non-printable characters in preference to the historical usage of, for instance, "^I"
for the <tab>. Implementations are encouraged to conform to historical practice in the
absence of any strong reason to diverge.
Historically, all ex commands beginning with the letter 'p' could be entered using
capitalized versions of the commands; for example, P[rint], Pre[serve], and Pu[t] were all
valid command names. POSIX.1‐2008 permits, but does not require, this historical practice
because capital forms of the commands are used by some implementations for other purposes.
Put
Historically, an ex put command, executed from open or visual mode, was the same as the
open or visual mode P command, if the buffer was named and was cut in character mode, and
the same as the p command if the buffer was named and cut in line mode. If the unnamed
buffer was the source of the text, the entire line from which the text was taken was
usually put, and the buffer was handled as if in line mode, but it was possible to get
extremely anomalous behavior. In addition, using the Q command to switch into ex mode, and
then doing a put often resulted in errors as well, such as appending text that was
unrelated to the (supposed) contents of the buffer. For consistency and simplicity of
specification, POSIX.1‐2008 does not permit these behaviors. All ex put commands are
required to operate in line mode, and the contents of the buffers are not altered by
changing the mode of the editor.
Read
Historically, an ex read command executed from open or visual mode, executed in an empty
file, left an empty line as the first line of the file. For consistency and simplicity of
specification, POSIX.1‐2008 does not permit this behavior. Historically, a read in open
or visual mode from a program left the cursor at the last line read in, not the first. For
consistency, POSIX.1‐2008 does not permit this behavior.
Historical implementations of ex were unable to undo read commands that read from the
output of a program. For consistency, POSIX.1‐2008 does not permit this behavior.
Historically, the ex and vi message after a successful read or write command specified
``characters'', not ``bytes''. POSIX.1‐2008 requires that the number of bytes be
displayed, not the number of characters, because it may be difficult in multi-byte
implementations to determine the number of characters read. Implementations are encouraged
to clarify the message displayed to the user.
Historically, reads were not permitted on files other than type regular, except that FIFO
files could be read (probably only because they did not exist when ex and vi were
originally written). Because the historical ex evaluated read! and read ! equivalently,
there can be no optional way to force the read. POSIX.1‐2008 permits, but does not
require, this behavior.
Recover
Some historical implementations of the editor permitted users to recover the edit buffer
contents from a previous edit session, and then exit without saving those contents (or
explicitly discarding them). The intent of POSIX.1‐2008 in requiring that the edit buffer
be treated as already modified is to prevent this user error.
Rewind
Historical implementations supported the rewind command when the user was editing the
first file in the list; that is, the file that the rewind command would edit. POSIX.1‐2008
requires conformance to historical practice.
Substitute
Historically, ex accepted an r option to the s command. The effect of the r option was to
use the last regular expression used in any command as the pattern, the same as the ~
command. The r option is not required by POSIX.1‐2008. Historically, the c and g options
were toggled; for example, the command :s/abc/def/ was the same as s/abc/def/ccccgggg.
For simplicity of specification, POSIX.1‐2008 does not permit this behavior.
The tilde command is often used to replace the last search RE. For example, in the
sequence:
s/red/blue/
/green
~
the ~ command is equivalent to:
s/green/blue/
Historically, ex accepted all of the following forms:
s/abc/def/
s/abc/def
s/abc/
s/abc
POSIX.1‐2008 requires conformance to this historical practice.
The s command presumes that the '^' character only occupies a single column in the
display. Much of the ex and vi specification presumes that the <space> only occupies a
single column in the display. There are no known character sets for which this is not
true.
Historically, the final column position for the substitute commands was based on previous
column movements; a search for a pattern followed by a substitution would leave the column
position unchanged, while a 0 command followed by a substitution would change the column
position to the first non-<blank>. For consistency and simplicity of specification,
POSIX.1‐2008 requires that the final column position always be set to the first
non-<blank>.
Set
Historical implementations redisplayed all of the options for each occurrence of the all
keyword. POSIX.1‐2008 permits, but does not require, this behavior.
Tag
No requirement is made as to where ex and vi shall look for the file referenced by the tag
entry. Historical practice has been to look for the path found in the tags file, based on
the current directory. A useful extension found in some implementations is to look based
on the directory containing the tags file that held the entry, as well. No requirement is
made as to which reference for the tag in the tags file is used. This is deliberate, in
order to permit extensions such as multiple entries in a tags file for a tag.
Because users often specify many different tags files, some of which need not be relevant
or exist at any particular time, POSIX.1‐2008 requires that error messages about problem
tags files be displayed only if the requested tag is not found, and then, only once for
each time that the tag edit option is changed.
The requirement that the current edit buffer be unmodified is only necessary if the file
indicated by the tag entry is not the same as the current file (as defined by the current
pathname). Historically, the file would be reloaded if the filename had changed, as well
as if the filename was different from the current pathname. For consistency and simplicity
of specification, POSIX.1‐2008 does not permit this behavior, requiring that the name be
the only factor in the decision.
Historically, vi only searched for tags in the current file from the current cursor to the
end of the file, and therefore, if the wrapscan option was not set, tags occurring before
the current cursor were not found. POSIX.1‐2008 considers this a bug, and implementations
are required to search for the first occurrence in the file, regardless.
Undo
The undo description deliberately uses the word ``modified''. The undo command is not
intended to undo commands that replace the contents of the edit buffer, such as edit,
next, tag, or recover.
Cursor positioning after the undo command was inconsistent in the historical vi, sometimes
attempting to restore the original cursor position (global, undo, and v commands), and
sometimes, in the presence of maps, placing the cursor on the last line added or changed
instead of the first. POSIX.1‐2008 requires a simplified behavior for consistency and
simplicity of specification.
Version
The version command cannot be exactly specified since there is no widely-accepted
definition of what the version information should contain. Implementations are encouraged
to do something reasonably intelligent.
Write
Historically, the ex and vi message after a successful read or write command specified
``characters'', not ``bytes''. POSIX.1‐2008 requires that the number of bytes be
displayed, not the number of characters because it may be difficult in multi-byte
implementations to determine the number of characters written. Implementations are
encouraged to clarify the message displayed to the user.
Implementation-defined tests are permitted so that implementations can make additional
checks; for example, for locks or file modification times.
Historically, attempting to append to a nonexistent file caused an error. It has been left
unspecified in POSIX.1‐2008 to permit implementations to let the write succeed, so that
the append semantics are similar to those of the historical csh.
Historical vi permitted empty edit buffers to be written. However, since the way vi got
around dealing with ``empty'' files was to always have a line in the edit buffer, no
matter what, it wrote them as files of a single, empty line. POSIX.1‐2008 does not permit
this behavior.
Historically, ex restored standard output and standard error to their values as of when ex
was invoked, before writes to programs were performed. This could disturb the terminal
configuration as well as be a security issue for some terminals. POSIX.1‐2008 does not
permit this, requiring that the program output be captured and displayed as if by the ex
print command.
Adjust Window
Historically, the line count was set to the value of the scroll option if the type
character was end-of-file. This feature was broken on most historical implementations long
ago, however, and is not documented anywhere. For this reason, POSIX.1‐2008 is resolutely
silent.
Historically, the z command was <blank>-sensitive and z + and z - did different things
than z+ and z- because the type could not be distinguished from a flag. (The commands z .
and z = were historically invalid.) POSIX.1‐2008 requires conformance to this historical
practice.
Historically, the z command was further <blank>-sensitive in that the count could not be
<blank>-delimited; for example, the commands z= 5 and z- 5 were also invalid. Because the
count is not ambiguous with respect to either the type character or the flags, this is not
permitted by POSIX.1‐2008.
Escape
Historically, ex filter commands only read the standard output of the commands, letting
standard error appear on the terminal as usual. The vi utility, however, read both
standard output and standard error. POSIX.1‐2008 requires the latter behavior for both ex
and vi, for consistency.
Shift Left and Shift Right
Historically, it was possible to add shift characters to increase the effect of the
command; for example, <<< outdented (or >>> indented) the lines 3 levels of indentation
instead of the default 1. POSIX.1‐2008 requires conformance to historical practice.
<control>‐D
Historically, the <control>‐D command erased the prompt, providing the user with an
unbroken presentation of lines from the edit buffer. This is not required by POSIX.1‐2008;
implementations are encouraged to provide it if possible. Historically, the <control>‐D
command took, and then ignored, a count. POSIX.1‐2008 does not permit this behavior.
Write Line Number
Historically, the ex = command, when executed in ex mode in an empty edit buffer, reported
0, and from open or visual mode, reported 1. For consistency and simplicity of
specification, POSIX.1‐2008 does not permit this behavior.
Execute
Historically, ex did not correctly handle the inclusion of text input commands (that is,
append, insert, and change) in executed buffers. POSIX.1‐2008 does not permit this
exclusion for consistency.
Historically, the logical contents of the buffer being executed did not change if the
buffer itself were modified by the commands being executed; that is, buffer execution did
not support self-modifying code. POSIX.1‐2008 requires conformance to historical practice.
Historically, the @ command took a range of lines, and the @ buffer was executed once per
line, with the current line ('.') set to each specified line. POSIX.1‐2008 requires
conformance to historical practice.
Some historical implementations did not notice if errors occurred during buffer execution.
This, coupled with the ability to specify a range of lines for the ex @ command, makes it
trivial to cause them to drop core. POSIX.1‐2008 requires that implementations stop
buffer execution if any error occurs, if the specified line doesn't exist, or if the
contents of the edit buffer itself are replaced (for example, the buffer executes the ex
:edit command).
Regular Expressions in ex
Historical practice is that the characters in the replacement part of the last s command—
that is, those matched by entering a '~' in the regular expression—were not further
expanded by the regular expression engine. So, if the characters contained the string
"a.," they would match 'a' followed by ".," and not 'a' followed by any character.
POSIX.1‐2008 requires conformance to historical practice.
Edit Options in ex
The following paragraphs describe the historical behavior of some edit options that were
not, for whatever reason, included in POSIX.1‐2008. Implementations are strongly
encouraged to only use these names if the functionality described here is fully supported.
extended The extended edit option has been used in some implementations of vi to provide
extended regular expressions instead of basic regular expressions This option
was omitted from POSIX.1‐2008 because it is not widespread historical practice.
flash The flash edit option historically caused the screen to flash instead of beeping
on error. This option was omitted from POSIX.1‐2008 because it is not found in
some historical implementations.
hardtabs The hardtabs edit option historically defined the number of columns between
hardware tab settings. This option was omitted from POSIX.1‐2008 because it was
believed to no longer be generally useful.
modeline The modeline (sometimes named modelines) edit option historically caused ex or
vi to read the five first and last lines of the file for editor commands. This
option is a security problem, and vendors are strongly encouraged to delete it
from historical implementations.
open The open edit option historically disallowed the ex open and visual commands.
This edit option was omitted because these commands are required by
POSIX.1‐2008.
optimize The optimize edit option historically expedited text throughput by setting the
terminal to not do automatic <carriage-return> characters when printing more
than one logical line of output. This option was omitted from POSIX.1‐2008
because it was intended for terminals without addressable cursors, which are
rarely, if ever, still used.
ruler The ruler edit option has been used in some implementations of vi to present a
current row/column ruler for the user. This option was omitted from POSIX.1‐2008
because it is not widespread historical practice.
sourceany The sourceany edit option historically caused ex or vi to source start-up files
that were owned by users other than the user running the editor. This option is
a security problem, and vendors are strongly encouraged to remove it from their
implementations.
timeout The timeout edit option historically enabled the (now standard) feature of only
waiting for a short period before returning keys that could be part of a macro.
This feature was omitted from POSIX.1‐2008 because its behavior is now standard,
it is not widely useful, and it was rarely documented.
verbose The verbose edit option has been used in some implementations of vi to cause vi
to output error messages for common errors; for example, attempting to move the
cursor past the beginning or end of the line instead of only alerting the
screen. (The historical vi only alerted the terminal and presented no message
for such errors. The historical editor option terse did not select when to
present error messages, it only made existing error messages more or less
verbose.) This option was omitted from POSIX.1‐2008 because it is not widespread
historical practice; however, implementors are encouraged to use it if they wish
to provide error messages for naive users.
wraplen The wraplen edit option has been used in some implementations of vi to specify
an automatic margin measured from the left margin instead of from the right
margin. This is useful when multiple screen sizes are being used to edit a
single file. This option was omitted from POSIX.1‐2008 because it is not
widespread historical practice; however, implementors are encouraged to use it
if they add this functionality.
autoindent, ai
Historically, the command 0a did not do any autoindentation, regardless of the current
indentation of line 1. POSIX.1‐2008 requires that any indentation present in line 1 be
used.
autoprint, ap
Historically, the autoprint edit option was not completely consistent or based solely on
modifications to the edit buffer. Exceptions were the read command (when reading from a
file, but not from a filter), the append, change, insert, global, and v commands, all of
which were not affected by autoprint, and the tag command, which was affected by
autoprint. POSIX.1‐2008 requires conformance to historical practice.
Historically, the autoprint option only applied to the last of multiple commands entered
using <vertical-line> delimiters; for example, delete <newline> was affected by autoprint,
but delete|version <newline> was not. POSIX.1‐2008 requires conformance to historical
practice.
autowrite, aw
Appending the '!' character to the ex next command to avoid performing an automatic write
was not supported in historical implementations. POSIX.1‐2008 requires that the behavior
match the other ex commands for consistency.
ignorecase, ic
Historical implementations of case-insensitive matching (the ignorecase edit option) lead
to counter-intuitive situations when uppercase characters were used in range expressions.
Historically, the process was as follows:
1. Take a line of text from the edit buffer.
2. Convert uppercase to lowercase in text line.
3. Convert uppercase to lowercase in regular expressions, except in character class
specifications.
4. Match regular expressions against text.
This would mean that, with ignorecase in effect, the text:
The cat sat on the mat
would be matched by
/^the/
but not by:
/^[A-Z]he/
For consistency with other commands implementing regular expressions, POSIX.1‐2008 does
not permit this behavior.
paragraphs, para
The ISO POSIX‐2:1993 standard made the default paragraphs and sections edit options
implementation-defined, arguing they were historically oriented to the UNIX system troff
text formatter, and a ``portable user'' could use the {, }, [[, ]], (, and ) commands in
open or visual mode and have the cursor stop in unexpected places. POSIX.1‐2008 specifies
their values in the POSIX locale because the unusual grouping (they only work when grouped
into two characters at a time) means that they cannot be used for general-purpose
movement, regardless.
readonly
Implementations are encouraged to provide the best possible information to the user as to
the read-only status of the file, with the exception that they should not consider the
current special privileges of the process. This provides users with a safety net because
they must force the overwrite of read-only files, even when running with additional
privileges.
The readonly edit option specification largely conforms to historical practice. The only
difference is that historical implementations did not notice that the user had set the
readonly edit option in cases where the file was already marked read-only for some reason,
and would therefore reinitialize the readonly edit option the next time the contents of
the edit buffer were replaced. This behavior is disallowed by POSIX.1‐2008.
report
The requirement that lines copied to a buffer interact differently than deleted lines is
historical practice. For example, if the report edit option is set to 3, deleting 3 lines
will cause a report to be written, but 4 lines must be copied before a report is written.
The requirement that the ex global, v, open, undo, and visual commands present reports
based on the total number of lines added or deleted during the command execution, and that
commands executed by the global and v commands not present reports, is historical
practice. POSIX.1‐2008 extends historical practice by requiring that buffer execution be
treated similarly. The reasons for this are two-fold. Historically, only the report by the
last command executed from the buffer would be seen by the user, as each new report would
overwrite the last. In addition, the standard developers believed that buffer execution
had more in common with global and v commands than it did with other ex commands, and
should behave similarly, for consistency and simplicity of specification.
showmatch, sm
The length of time the cursor spends on the matching character is unspecified because the
timing capabilities of systems are often inexact and variable. The time should be long
enough for the user to notice, but not long enough for the user to become annoyed. Some
implementations of vi have added a matchtime option that permits users to set the number
of 0,1 second intervals the cursor pauses on the matching character.
showmode
The showmode option has been used in some historical implementations of ex and vi to
display the current editing mode when in open or visual mode. The editing modes have
generally included ``command'' and ``input'', and sometimes other modes such as
``replace'' and ``change''. The string was usually displayed on the bottom line of the
screen at the far right-hand corner. In addition, a preceding '*' character often denoted
whether the contents of the edit buffer had been modified. The latter display has
sometimes been part of the showmode option, and sometimes based on another option. This
option was not available in the 4 BSD historical implementation of vi, but was viewed as
generally useful, particularly to novice users, and is required by POSIX.1‐2008.
The smd shorthand for the showmode option was not present in all historical
implementations of the editor. POSIX.1‐2008 requires it, for consistency.
Not all historical implementations of the editor displayed a mode string for command mode,
differentiating command mode from text input mode by the absence of a mode string.
POSIX.1‐2008 permits this behavior for consistency with historical practice, but
implementations are encouraged to provide a display string for both modes.
slowopen
Historically, the slowopen option was automatically set if the terminal baud rate was less
than 1200 baud, or if the baud rate was 1200 baud and the redraw option was not set. The
slowopen option had two effects. First, when inserting characters in the middle of a line,
characters after the cursor would not be pushed ahead, but would appear to be overwritten.
Second, when creating a new line of text, lines after the current line would not be
scrolled down, but would appear to be overwritten. In both cases, ending text input mode
would cause the screen to be refreshed to match the actual contents of the edit buffer.
Finally, terminals that were sufficiently intelligent caused the editor to ignore the
slowopen option. POSIX.1‐2008 permits most historical behavior, extending historical
practice to require slowopen behaviors if the edit option is set by the user.
tags
The default path for tags files is left unspecified as implementations may have their own
tags implementations that do not correspond to the historical ones. The default tags
option value should probably at least include the file ./tags.
term
Historical implementations of ex and vi ignored changes to the term edit option after the
initial terminal information was loaded. This is permitted by POSIX.1‐2008; however,
implementations are encouraged to permit the user to modify their terminal type at any
time.
terse
Historically, the terse edit option optionally provided a shorter, less descriptive error
message, for some error messages. This is permitted, but not required, by POSIX.1‐2008.
Historically, most common visual mode errors (for example, trying to move the cursor past
the end of a line) did not result in an error message, but simply alerted the terminal.
Implementations wishing to provide messages for novice users are urged to do so based on
the edit option verbose, and not terse.
window
In historical implementations, the default for the window edit option was based on the
baud rate as follows:
1. If the baud rate was less than 1200, the edit option w300 set the window value; for
example, the line:
set w300=12
would set the window option to 12 if the baud rate was less than 1200.
2. If the baud rate was equal to 1200, the edit option w1200 set the window value.
3. If the baud rate was greater than 1200, the edit option w9600 set the window value.
The w300, w1200, and w9600 options do not appear in POSIX.1‐2008 because of their
dependence on specific baud rates.
In historical implementations, the size of the window displayed by various commands was
related to, but not necessarily the same as, the window edit option. For example, the size
of the window was set by the ex command visual 10, but it did not change the value of the
window edit option. However, changing the value of the window edit option did change the
number of lines that were displayed when the screen was repainted. POSIX.1‐2008 does not
permit this behavior in the interests of consistency and simplicity of specification, and
requires that all commands that change the number of lines that are displayed do it by
setting the value of the window edit option.
wrapmargin, wm
Historically, the wrapmargin option did not affect maps inserting characters that also had
associated counts; for example :map K 5aABC DEF. Unfortunately, there are widely used
maps that depend on this behavior. For consistency and simplicity of specification,
POSIX.1‐2008 does not permit this behavior.
Historically, wrapmargin was calculated using the column display width of all characters
on the screen. For example, an implementation using "^I" to represent <tab> characters
when the list edit option was set, where '^' and 'I' each took up a single column on the
screen, would calculate the wrapmargin based on a value of 2 for each <tab>. The number
edit option similarly changed the effective length of the line as well. POSIX.1‐2008
requires conformance to historical practice.
Earlier versions of this standard allowed for implementations with bytes other than eight
bits, but this has been modified in this version.
FUTURE DIRECTIONS
None.
SEE ALSO
Section 2.9.1.1, Command Search and Execution, ctags, ed, sed, sh, stty, vi
The Base Definitions volume of POSIX.1‐2017, Table 5-1, Escape Sequences and Associated
Actions, Chapter 8, Environment Variables, Section 9.3, Basic Regular Expressions, Section
12.2, Utility Syntax Guidelines
The System Interfaces volume of POSIX.1‐2017, access()
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std
1003.1-2017, Standard for Information Technology -- Portable Operating System Interface
(POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by
the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and The Open Group
Standard, the original IEEE and The Open Group Standard is the referee document. The
original Standard can be obtained online at http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page are most likely to have
been introduced during the conversion of the source files to man page format. To report
such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .