-.TH MH-SEQUENCE %manext5% "%nmhdate%" MH.6.8 [%nmhversion%]
+.TH MH-SEQUENCE %manext5% "June 11, 2013" "%nmhversion%"
.\"
.\" %nmhwarning%
.\"
.SH NAME
mh-sequence \- sequence specification for nmh message system
-.SH SYNOPSIS
-most
-.B nmh
-commands
.SH DESCRIPTION
A sequence (or sequence set) is a symbolic name representing a
message or collection of messages.
or one of these \*(lqreserved\*(rq message names:
.PP
.RS 5
-.nf
-.ta +\w'\fIName\fP 'u
-.I "Name Description"
-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 \*(lqcur\*(rq
-next the message numerically following \*(lqcur\*(rq
-.fi
+.PD 0
+.TP
+.B first
+the first message in the folder
+.TP
+.B last
+the last message in the folder
+.TP
+.B cur
+the most recently accessed message
+.TP
+.B prev
+the message numerically preceding \*(lqcur\*(rq
+.TP
+.B next
+the message numerically following \*(lqcur\*(rq
.RE
+.PD
.PP
In commands that take a `msg' argument, the default is \*(lqcur\*(rq.
As a shorthand, \*(lq\&.\*(rq is equivalent to \*(lqcur\*(rq.
.PP
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 separated by spaces. A message designation consists
+message designations, as separate arguments. A message designation consists
either of a message name as defined above, or a message range.
.PP
A message range is specified as \*(lqname1\-name2\*(rq or
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'.
.PP
+Substituting `=' for `:' (i.e., \*(lqname=n\*(rq) 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 \*(lqname:-3\*(rq
+selects the 3 messages ending with `name', \*(lqname=-3\*(rq 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).
+.PP
In commands which accept a `msgs' argument, the default is either
\*(lqcur\*(rq or \*(lqall\*(rq, depending on which makes more sense
for each command (see the individual man pages for details). Repeated
instead). The syntax of these message range specifications is subject
to change in the future.
.PP
+Single messages (as opposed to ranges) may also be selected by
+substituting `=' for `:', as in \*(lqname=n\*(rq. 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 \*(lqseq:5\*(rq
+selects the first 5 messages of seqence `seq', \*(lqseq=5\*(rq
+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).
+.PP
User-defined sequence names are specific to each folder. They are
defined using the
.B pick
should be defined in the
.B nmh
profile; its value should be a sequence
-name or multiple sequence names separated by spaces. If this entry
+name or multiple sequence names, as separate arguments. If this entry
is defined, when when an
.B nmh
command finishes, it will define the
in the
.I \&.mh\(ruprofile
should be defined as one or more sequence
-names separated by spaces. If there is a value for
+names, as separate arguments. If there is a value for
\*(lqUnseen\-Sequence\*(rq in the profile, then whenever new messages
are placed in a folder (using
.B inc
displays a message, that message will be removed from
any sequences named by the \*(lqUnseen\-Sequence\*(rq entry in the
profile.
-.SH FILES
-.fc ^ ~
+.SS 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 \*(lqlownum\-highnum\*(rq.
+.PP
+.B Sample sequence file
+.PP
+.RS 5
.nf
-.ta \w'%etcdir%/ExtraBigFileName 'u
-^$HOME/\&.mh\(ruprofile~^The user profile
-^<mh\-dir>/context~^The user context
-^<folder>/\&.mh\(rusequences~^File for public sequences
+work: 3 6 8 22-33 46
+unseen: 47 49-51 54
+cur: 46
.fi
+.RE
+.PP
+.B 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 \*(lqcur\*(rq sequence, which is allowed to point to a
+nonexistent message.
+.SS Sequence File Locking
+The \*(lqdatalocking\*(rq profile entry controls the type of locking used
+when reading and writing sequence files. The locking mechanisms supported
+are detailed in
+.IR mh\-profile (5).
+This protects sequence file integrity when multiple
+.B nmh
+commands are run simultaneously.
+.B 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
+.B nmh
+commands, such as
+.B inc
+and
+.BR 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.
+.PP
+.B Note:
+Currently transactional locks are
+.B only
+supported for public sequences; private sequences will not get corrupted, but
+the possibility exists that two
+.B nmh
+commands run simultaneously that add messages to a private sequence could result in
+one command's messages not appearing on the requested sequence.
+.SH FILES
+.PD 0
+.TP 20
+$HOME/\&.mh\-profile
+The user's profile.
+.TP 20
+<mh\-dir>/context
+The user's context.
+.TP 20
+<folder>/\&.mh\-sequences
+File for public sequences.
+.PD
.SH "PROFILE COMPONENTS"
-.fc ^ ~
-.nf
-.ta 2.4i
-.ta \w'ExtraBigProfileName 'u
-^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
-.fi
+.PD 0
+.TP 20
+mh-sequences:
+Name of file to store public sequences.
+.TP 20
+Sequence\-Negation:
+To designate messages not in a sequence.
+.TP 20
+Previous\-Sequence:
+The last message specification given.
+.TP 20
+Unseen\-Sequence:
+Those messages not yet seen by the user.
+.PD
.SH "SEE ALSO"
.IR flist (1),
.IR mark (1),
projects / nmh / blobdiff