mh-sequence - sequence specification for mh message system
A sequence (or sequence set) is a symbolic name representing a message or collection of messages. mmh has several internally defined sequences, as well as allowing users to define their own sequences.
Message Specification and Pre-Defined Message Sequences¶
Most mmh 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 f the first message in the folder p the message numerically preceding `c' c the most recently accessed message n the message numerically following `c' l the last message in the folder
In commands that take a `msg' argument, the default is `c'.
For example: In a folder containing five messages numbered 5, 10, 94, 177 and 325, `f' is 5 and `l' is 325. If `c' is 94, then `p' is 10 and `n' 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:i', where `name', `name1' and `name2' are message names, and `i' is an integer.
The specification `name1-name2' designates all currently existing messages from `name1' to `name2' inclusive. The `reserved' message name `a' (``all'') is a shorthand for the message range `f-l'.
Name Description a all messages in the folder (i.e. `f-l')
The specification `name:i' designates up to `i' messages. These messages start with `name' if `name' is a message number or one of the reserved names `f' `c', or `n', The messages end with `name' if `name' is `p' or `l'. The interpretation of `i' may be overridden by preceding `i' with a plus or minus sign; `+i' always means up to `i' messages starting with `name', and `-i' always means up to `i' messages ending with `name'.
In commands which accept a `msgs' argument, the default is either `c' or `a', 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 `b' (``beyond'') which can be used with the mhpath command. It refers to the next (not yet used) message number after `l'.
Name Description b the next message number beyond `l'
User-Defined Message Sequences¶
In addition to the `reserved' (pre-defined) message names given above, mmh supports user-defined sequence names. User-defined sequences allow the mmh 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 mmh command expects a `msg' or `msgs' argument.
Some forms of message ranges are allowed with user-defined sequences. The specification `name:i' may be used, and it designates up to the first `i' messages (or last `i' messages for `-i') which are elements of the user-defined sequence `name'.
The specifications `name:n' and `name:p' 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:f' and `name:l' are equivalent to `name:1' and `name:-1', respectively. The specification `name:c' is not allowed (use just `c' instead). Note: 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 mmh 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 mmh user that defined those sequences and are kept in the user's mh 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 mmh 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.
Mmh provides the ability to select all messages not elements of a user-defined sequence. A special string is used to preface an existing user-defined sequence name. This specification then refers to those messages not elements of the specified sequence name. The default negation prefix is the exlamation mark `!', but it may be change to any string, by defining the entry `Sequence-Negation' in the mmh profile file. For example, if the profile entry is:
then anytime an mmh 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 default value `!' was chosen due to its similar meaning in the C programming language, and because it cannot be part of a user-defined sequence. But if your shell provides history expansion, you might need to quote the exlamation mark (prefix it with a backslash).
To deactivate the negation mechanism, define Sequence-Negation in your profile to an empty value.
The Previous Sequence¶
Mmh provides the ability to remember the `msgs' or `msg' argument last given to an mmh command. The entry `Previous-Sequence' should be defined in the mmh profile; its value should be a sequence name or multiple sequence names separated by spaces. If this entry is defined, when an mmh 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
directs any mmh 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 mmh 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, the unseen sequence indicates which messages have not
been previously seen by the user. The commands inc, rcvstore,
show, and flist honor the sequence. Whenever new messages are
placed in a folder (using inc or rcvstore), the new messages
will also be added to the unseen sequence.
inc, for example, adds new messages to the unseen sequence. Unlike the behavior of the previous sequence, however, the unseen sequence will not be zeroed by inc.
Similarly, whenever show, next, or prev display a message, that message will be removed from the unseen sequence.
The default unseen sequence is named `u'. To change, define a `Unseen-Sequence' entry in your profile. It may also contain multiple sequence names, separated by spaces. In this case, anything that applied to a single unseen sequence, applies to multiple ones, too.
The unseen sequence mechanism is automatically activated. To deactivate it, define the `Unseen-Sequence' entry in your profile with an empty value.
^$HOME/.mmh/profile~^The user profile ^$HOME/.mmh/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