mh-sequence(5) sequence specification for nmh message system


most nmh commands


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:

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 ``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 separated by spaces. 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 ``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 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 `name'.

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.

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 anytime 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 separated by spaces. If this entry is defined, when 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 inc, rcvstore, show, mhshow, and flist 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 separated by spaces. 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 inc.

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.


^$HOME/.mh_profile~^The user profile
^<mh-dir>/context~^The user context
^<folder>/.mh_sequences~^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