man > mh-sequence(5)

MH-SEQUENCE(5mh)                                                                    MH-SEQUENCE(5mh)

NAME
       mh-sequence - sequence specification for nmh message system

DESCRIPTION
       A  sequence (or sequence set) is a symbolic name representing a message or collection of mes‐
       sages.  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 equiva‐
       lent 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  argu‐
       ments.   A  message designation consists either of a message name as defined above, or a mes‐
       sage 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
       “first-last”.

       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 mes‐
       sages end with `name' if `name' is “prev” or “last”.  The interpretation of `n' may be  over‐
       ridden  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 `name'.

       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).  Re‐
       peated 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-de‐
       fined 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” in‐
       stead).  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 be‐
       ing 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 se‐
       quences 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  se‐
       quence  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  sub‐
       stitute 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  com‐
       mand.   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  de‐
       fined,  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 se‐
       quence names, as separate arguments.  If there is a value for “Unseen-Sequence” in  the  pro‐
       file, then whenever new messages are placed in a folder (using inc or rcvstore), the new mes‐
       sages  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 “Previ‐
       ous-Sequence” entry in the profile, however, the sequence(s) will not be zeroed by inc.

       Similarly, whenever show, mhshow, next, or prev displays a message, that message will be  re‐
       moved 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  pro‐
       tects  sequence  file  integrity when multiple nmh commands are run simultaneously.  Nmh com‐
       mands 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  run‐
       time  and  reread  the  sequence  file after their processing is complete to reduce lock con‐
       tention time.

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

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

PROFILE COMPONENTS
       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.

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

DEFAULTS
       None

nmh-1.8                                      2013-10-17                             MH-SEQUENCE(5mh)