-.TH MH-SEQUENCE %manext5% "%nmhdate%" MH.6.8 [%nmhversion%]
+.TH MH-SEQUENCE %manext5% "January 9, 2001" "%nmhversion%"
.\"
.\" %nmhwarning%
.\"
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
displays a message, that message will be removed from
any sequences named by the \*(lqUnseen\-Sequence\*(rq entry in the
profile.
+.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
.fc ^ ~
.nf
^Unseen\-Sequence:~^Those messages not yet seen by the user
.fi
.SH "SEE ALSO"
-flist(1), mark(1), pick(1), mh-profile(5)
+.IR flist (1),
+.IR mark (1),
+.IR pick (1),
+.IR mh-profile (5)
.SH DEFAULTS
None