Provided by: nmh_1.7.1-12_amd64 bug


       mh-sequence - sequence specification for nmh message system


       A  sequence  (or  sequence set) is a symbolic name representing a message or collection of
       messages.  nmh has several internally defined sequences, as  well  as  allowing  users  to
       define their own sequences.

   Message Specification and Pre-Defined Message Sequences
       Most  nmh  commands  accept  a  `msg'  or  `msgs' specification, where `msg' indicates one
       message and `msgs' indicates one or more messages.  To designate a message,  you  may  use
       either its number (e.g., 1, 10, 234) or one of these “reserved” message names:

            first  the first message in the folder
            last   the last message in the folder
            cur    the most recently accessed message
            prev   the message numerically preceding “cur”
            next   the message numerically following “cur”

       In  commands  that  take  a  `msg' argument, the default is “cur”.  As a shorthand, “.” is
       equivalent to “cur”.

       For example: In a folder containing five messages numbered 5, 10, 94, 177 and 325, “first”
       is 5 and “last” is 325.  If “cur” is 94, then “prev” is 10 and “next” is 177.

       The  word  `msgs'  indicates  that  one  or  more  messages  may  be  specified.   Such  a
       specification consists of one message designation or of several message  designations,  as
       separate  arguments.   A  message designation consists either of a message name as defined
       above, or a message range.

       A message range is specified as “name1-name2”  or  “name:n”,  where  `name',  `name1'  and
       `name2' are message names, and `n' is an integer.

       The specification “name1-name2” designates all currently existing messages from `name1' to
       `name2' inclusive.  The “reserved” message name “all” is a shorthand for the message range

       The  specification  “name:n”  designates  up  to  `n' messages.  These messages start with
       `name' if `name' is a message number or one  of  the  reserved  names  “first”  “cur”,  or
       “next”, The messages end with `name' if `name' is “prev” or “last”.  The interpretation of
       `n' may be overridden by preceding `n' with a plus or minus sign; `+n' always means up  to
       `n'  messages  starting  with `name', and `-n' always means up to `n' messages ending with

       Substituting `=' for `:' (i.e., “name=n”) will reduce the selection from a range of up  to
       `n'  messages,  to a selection of just the `n'th message.  So for example, while “name:-3”
       selects the 3 messages ending  with  `name',  “name=-3”  selects  just  the  2nd  previous
       message.   It  is  an  error  if  the requested message does not exist (i.e., there aren't
       enough messages in the folder).

       In commands which accept a  `msgs'  argument,  the  default  is  either  “cur”  or  “all”,
       depending  on  which  makes  more sense for each command (see the individual man pages for
       details).  Repeated specifications of the same message have the same effect  as  a  single
       specification of the message.

       There is also a special “reserved” message name “new” which is used by the mhpath command.

   User-Defined Message Sequences
       In  addition to the “reserved” (pre-defined) message names given above, nmh supports user-
       defined sequence names.  User-defined sequences allow the nmh user a tremendous amount  of
       power in dealing with groups of messages in the same folder by allowing the user to bind a
       group of messages to a meaningful symbolic name.

       The name used to denote a  message  sequence  must  consist  of  an  alphabetic  character
       followed  by  zero  or  more alphanumeric characters, and can not be one of the “reserved”
       message names above.  After defining a sequence, it can be used wherever  an  nmh  command
       expects a `msg' or `msgs' argument.

       Some  forms  of message ranges are allowed with user-defined sequences.  The specification
       “name:n” may be used, and it designates up to the first `n' messages (or last `n' messages
       for `-n') which are elements of the user-defined sequence `name'.

       The  specifications  “name:next”  and “name:prev” may also be used, and they designate the
       next or previous message (relative to the current message) which  is  an  element  of  the
       user-defined  sequence  `name'.   The  specifications  “name:first”  and  “name:last”  are
       equivalent to “name:1” and “name:-1”, respectively.  The specification “name:cur”  is  not
       allowed  (use  just  “cur”  instead).  The syntax of these message range specifications is
       subject to change in the future.

       Single messages (as opposed to ranges) may also be selected by substituting `='  for  `:',
       as  in “name=n”.  This will reduce the selection from being a range of up to `n' messages,
       to being a selection of just the `n'th message.  So while  “seq:5”  selects  the  first  5
       messages  of  sequence `seq', “seq=5” selects just the 5th message of the sequence.  It is
       an error if the requested message does not exist (i.e., there aren't at least `n' messages
       in the sequence).

       User-defined  sequence names are specific to each folder.  They are defined using the pick
       and mark commands.

   Public and Private User-Defined Sequences
       There are two varieties of user-defined sequences: public and private.   Public  sequences
       of  a  folder  are accessible to any nmh user that can read that folder.  They are kept in
       each folder in the file  determined  by  the  “mh-sequences”  profile  entry  (default  is
       .mh_sequences).   Private sequences are accessible only to the nmh user that defined those
       sequences and are kept in the user's nmh context file.

       In general, the commands that create sequences (such as pick and mark) will create  public
       sequences  if  the folder for which the sequences are being defined is writable by the nmh
       user.  For most commands, this can  be  overridden  by  using  the  switches  -public  and
       -private.   But  if  the  folder  is  read-only, or if the “mh-sequences” profile entry is
       defined but empty, then private sequences will be created instead.

   Sequence Negation
       Nmh provides the ability to select all messages not elements of a  user-defined  sequence.
       To  do this, the user should define the entry “Sequence-Negation” in the nmh profile file;
       its value may be any string.  This string is then used to preface an existing user-defined
       sequence  name.   This  specification  then  refers  to those messages not elements of the
       specified sequence name.  For example, if the profile entry is:

            Sequence-Negation: not

       then any time an nmh command is given “notfoo” as a `msg' or  `msgs'  argument,  it  would
       substitute all messages that are not elements of the sequence “foo”.

       Obviously,  the  user  should  beware of defining sequences with names that begin with the
       value of the “Sequence-Negation” profile entry.

   The Previous Sequence
       Nmh provides the ability to remember the `msgs' or `msg' argument last  given  to  an  nmh
       command.   The  entry  “Previous-Sequence” should be defined in the nmh profile; its value
       should be a sequence name or multiple sequence names,  as  separate  arguments.   If  this
       entry  is  defined,  when an nmh command finishes, it will define the sequence(s) named in
       the value of this entry to be those messages that were specified to the command.  Hence, a
       profile entry of

            Previous-Sequence: pseq

       directs  any  nmh  command  that accepts a `msg' or `msgs' argument to define the sequence
       “pseq” as those messages when it finishes.

       Note: there can be a performance penalty in using the “Previous-Sequence” facility.  If it
       is used, all nmh programs have to write the sequence information to the .mh_sequences file
       for the folder each time they run.   If  the  “Previous-Sequence”  profile  entry  is  not
       included, only pick and mark will write to the .mh_sequences file.

   The Unseen Sequence
       Finally, many users like to indicate which messages have not been previously seen by them.
       The  commands  flist,  inc,  mhshow,  rcvstore,  and  show   honor   the   profile   entry
       “Unseen-Sequence”  to  support  this  activity.   This  entry in the .mh_profile should be
       defined as one or more sequence names, as separate arguments.  If there  is  a  value  for
       “Unseen-Sequence” in the profile, then whenever new messages are placed in a folder (using
       inc or rcvstore), the new messages will also be added to all the sequences named  in  this
       profile entry.  For example, a profile entry of

            Unseen-Sequence: unseen

       directs  inc  to  add  new  messages to the sequence “unseen”.  Unlike the behavior of the
       “Previous-Sequence” entry in the profile, however, the sequence(s) will not be  zeroed  by

       Similarly,  whenever  show, mhshow, next, or prev displays a message, that message will be
       removed from any sequences named by the “Unseen-Sequence” entry in the profile.

   Sequence File Format
       The sequence file format is based on the RFC  5322  message  format.   Each  line  of  the
       sequence  file  corresponds  to  one  sequence.   The  line  starts with the sequence name
       followed by a `:', then followed  by  a  space-separated  list  of  message  numbers  that
       correspond  to  messages  that  are  part  of  the  named sequence.  A contiguous range of
       messages can be represented as “lownum-highnum”.

       Sample sequence file

            work: 3 6 8 22-33 46
            unseen: 47 49-51 54
            cur: 46

       Nmh commands that modify the sequence file will silently remove sequences for  nonexistent
       messages  when the sequence file is updated.  The exception to this is the “cur” sequence,
       which is allowed to point to a nonexistent message.

   Sequence File Locking
       The “datalocking” profile entry controls the type of locking used when reading and writing
       sequence  files.   The  locking  mechanisms supported are detailed in mh-profile(5).  This
       protects sequence file integrity when multiple nmh commands are run  simultaneously.   Nmh
       commands  that modify the sequence file use transactional locks; the lock is held from the
       time the sequence file is read until it it written out.  This ensures  that  modifications
       to  the sequence file will not be lost if multiple commands are run simultaneously.  Long-
       running nmh commands, such as inc and pick, will release the sequence lock during the bulk
       of their runtime and reread the sequence file after their processing is complete to reduce
       lock contention time.

       Note: Currently transactional locks are  only  supported  for  public  sequences;  private
       sequences  will  not  get  corrupted, but the possibility exists that two nmh commands run
       simultaneously that add messages to a private  sequence  could  result  in  one  command's
       messages not appearing on the requested sequence.


       $HOME/.mh-profile   The user's profile.
       <mh-dir>/context    The user's context.
                           File for public sequences.


       mh-sequences:       Name of file to store public sequences.
       Sequence-Negation:  To designate messages not in a sequence.
       Previous-Sequence:  The last message specification given.
       Unseen-Sequence:    Those messages not yet seen by the user.


       flist(1), mark(1), pick(1), mh-profile(5)