1MH-SEQUENCE(5) File Formats Manual MH-SEQUENCE(5)
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6 mh-sequence - sequence specification for nmh message system
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9 A sequence (or sequence set) is a symbolic name representing a message
10 or collection of messages. nmh has several internally defined se‐
11 quences, as well as allowing users to define their own sequences.
12 Message Specification and Pre-Defined Message Sequences
14 Most nmh commands accept a `msg' or `msgs' specification, where `msg'
15 indicates one message and `msgs' indicates one or more messages. To
16 designate a message, you may use either its number (e.g., 1, 10, 234)
17 or one of these “reserved” message names:
18 first the first message in the folder
20 last the last message in the folder
21 cur the most recently accessed message
22 prev the message numerically preceding “cur”
23 next the message numerically following “cur”
24 In commands that take a `msg' argument, the default is “cur”. As a
26 shorthand, “.” is equivalent to “cur”.
27 For example: In a folder containing five messages numbered 5, 10, 94,
29 177 and 325, “first” is 5 and “last” is 325. If “cur” is 94, then
30 “prev” is 10 and “next” is 177.
31 The word `msgs' indicates that one or more messages may be specified.
33 Such a specification consists of one message designation or of several
34 message designations, as separate arguments. A message designation
35 consists either of a message name as defined above, or a message range.
36 A message range is specified as “name1-name2” or “name:n”, where
38 `name', `name1' and `name2' are message names, and `n' is an integer.
39 The specification “name1-name2” designates all currently existing mes‐
41 sages from `name1' to `name2' inclusive. The “reserved” message name
42 “all” is a shorthand for the message range “first-last”.
43 The specification “name:n” designates up to `n' messages. These mes‐
45 sages start with `name' if `name' is a message number or one of the re‐
46 served names “first” “cur”, or “next”, The messages end with `name' if
47 `name' is “prev” or “last”. The interpretation of `n' may be overrid‐
48 den by preceding `n' with a plus or minus sign; `+n' always means up to
49 `n' messages starting with `name', and `-n' always means up to `n' mes‐
50 sages ending with `name'.
51 Substituting `=' for `:' (i.e., “name=n”) will reduce the selection
53 from a range of up to `n' messages, to a selection of just the `n'th
54 message. So for example, while “name:-3” selects the 3 messages ending
55 with `name', “name=-3” selects just the 2nd previous message. It is an
56 error if the requested message does not exist (i.e., there aren't
57 enough messages in the folder).
58 In commands which accept a `msgs' argument, the default is either “cur”
60 or “all”, depending on which makes more sense for each command (see the
61 individual man pages for details). Repeated specifications of the same
62 message have the same effect as a single specification of the message.
63 There is also a special “reserved” message name “new” which is used by
65 the mhpath command.
66 User-Defined Message Sequences
68 In addition to the “reserved” (pre-defined) message names given above,
69 nmh supports user-defined sequence names. User-defined sequences allow
70 the nmh user a tremendous amount of power in dealing with groups of
71 messages in the same folder by allowing the user to bind a group of
72 messages to a meaningful symbolic name.
73 The name used to denote a message sequence must consist of an alpha‐
75 betic character followed by zero or more alphanumeric characters, and
76 can not be one of the “reserved” message names above. After defining a
77 sequence, it can be used wherever an nmh command expects a `msg' or
78 `msgs' argument.
79 Some forms of message ranges are allowed with user-defined sequences.
81 The specification “name:n” may be used, and it designates up to the
82 first `n' messages (or last `n' messages for `-n') which are elements
83 of the user-defined sequence `name'.
84 The specifications “name:next” and “name:prev” may also be used, and
86 they designate the next or previous message (relative to the current
87 message) which is an element of the user-defined sequence `name'. The
88 specifications “name:first” and “name:last” are equivalent to “name:1”
89 and “name:-1”, respectively. The specification “name:cur” is not al‐
90 lowed (use just “cur” instead). The syntax of these message range
91 specifications is subject to change in the future.
92 Single messages (as opposed to ranges) may also be selected by substi‐
94 tuting `=' for `:', as in “name=n”. This will reduce the selection
95 from being a range of up to `n' messages, to being a selection of just
96 the `n'th message. So while “seq:5” selects the first 5 messages of
97 sequence `seq', “seq=5” selects just the 5th message of the sequence.
98 It is an error if the requested message does not exist (i.e., there
99 aren't at least `n' messages in the sequence).
100 User-defined sequence names are specific to each folder. They are de‐
102 fined using the pick and mark commands.
103 Public and Private User-Defined Sequences
105 There are two varieties of user-defined sequences: public and private.
106 Public sequences of a folder are accessible to any nmh user that can
107 read that folder. They are kept in each folder in the file determined
108 by the “mh-sequences” profile entry (default is .mh_sequences). Pri‐
109 vate sequences are accessible only to the nmh user that defined those
110 sequences and are kept in the user's nmh context file.
111 In general, the commands that create sequences (such as pick and mark)
113 will create public sequences if the folder for which the sequences are
114 being defined is writable by the nmh user. For most commands, this can
115 be overridden by using the switches -public and -private. But if the
116 folder is read-only, or if the “mh-sequences” profile entry is defined
117 but empty, then private sequences will be created instead.
118 Sequence Negation
120 Nmh provides the ability to select all messages not elements of a user-
121 defined sequence. To do this, the user should define the entry “Se‐
122 quence-Negation” in the nmh profile file; its value may be any string.
123 This string is then used to preface an existing user-defined sequence
124 name. This specification then refers to those messages not elements of
125 the specified sequence name. For example, if the profile entry is:
126 Sequence-Negation: not
128 then any time an nmh command is given “notfoo” as a `msg' or `msgs' ar‐
130 gument, it would substitute all messages that are not elements of the
131 sequence “foo”.
132 Obviously, the user should beware of defining sequences with names that
134 begin with the value of the “Sequence-Negation” profile entry.
135 The Previous Sequence
137 Nmh provides the ability to remember the `msgs' or `msg' argument last
138 given to an nmh command. The entry “Previous-Sequence” should be de‐
139 fined in the nmh profile; its value should be a sequence name or multi‐
140 ple sequence names, as separate arguments. If this entry is defined,
141 when an nmh command finishes, it will define the sequence(s) named in
142 the value of this entry to be those messages that were specified to the
143 command. Hence, a profile entry of
144 Previous-Sequence: pseq
146 directs any nmh command that accepts a `msg' or `msgs' argument to de‐
148 fine the sequence “pseq” as those messages when it finishes.
149 Note: there can be a performance penalty in using the “Previous-Se‐
151 quence” facility. If it is used, all nmh programs have to write the
152 sequence information to the .mh_sequences file for the folder each time
153 they run. If the “Previous-Sequence” profile entry is not included,
154 only pick and mark will write to the .mh_sequences file.
155 The Unseen Sequence
157 Finally, many users like to indicate which messages have not been pre‐
158 viously seen by them. The commands flist, inc, mhshow, rcvstore, and
159 show honor the profile entry “Unseen-Sequence” to support this activ‐
160 ity. This entry in the .mh_profile should be defined as one or more
161 sequence names, as separate arguments. If there is a value for “Un‐
162 seen-Sequence” in the profile, then whenever new messages are placed in
163 a folder (using inc or rcvstore), the new messages will also be added
164 to all the sequences named in this profile entry. For example, a pro‐
165 file entry of
166 Unseen-Sequence: unseen
168 directs inc to add new messages to the sequence “unseen”. Unlike the
170 behavior of the “Previous-Sequence” entry in the profile, however, the
171 sequence(s) will not be zeroed by inc.
172 Similarly, whenever show, mhshow, next, or prev displays a message,
174 that message will be removed from any sequences named by the “Un‐
175 seen-Sequence” entry in the profile.
176 Sequence File Format
178 The sequence file format is based on the RFC 5322 message format. Each
179 line of the sequence file corresponds to one sequence. The line starts
180 with the sequence name followed by a `:', then followed by a space-sep‐
181 arated list of message numbers that correspond to messages that are
182 part of the named sequence. A contiguous range of messages can be rep‐
183 resented as “lownum-highnum”.
184 Sample sequence file
186 work: 3 6 8 22-33 46
188 unseen: 47 49-51 54
189 cur: 46
190 Nmh commands that modify the sequence file will silently remove se‐
192 quences for nonexistent messages when the sequence file is updated.
193 The exception to this is the “cur” sequence, which is allowed to point
194 to a nonexistent message.
195 Sequence File Locking
197 The “datalocking” profile entry controls the type of locking used when
198 reading and writing sequence files. The locking mechanisms supported
199 are detailed in mh-profile(5). This protects sequence file integrity
200 when multiple nmh commands are run simultaneously. Nmh commands that
201 modify the sequence file use transactional locks; the lock is held from
202 the time the sequence file is read until it it written out. This en‐
203 sures that modifications to the sequence file will not be lost if mul‐
204 tiple commands are run simultaneously. Long-running nmh commands, such
205 as inc and pick, will release the sequence lock during the bulk of
206 their runtime and reread the sequence file after their processing is
207 complete to reduce lock contention time.
208 Note: Currently transactional locks are only supported for public se‐
210 quences; private sequences will not get corrupted, but the possibility
211 exists that two nmh commands run simultaneously that add messages to a
212 private sequence could result in one command's messages not appearing
213 on the requested sequence.
214
216 $HOME/.mh-profile The user's profile.
217 <mh-dir>/context The user's context.
218 <folder>/.mh-sequences
219 File for public sequences.
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222 mh-sequences: Name of file to store public sequences.
223 Sequence-Negation: To designate messages not in a sequence.
224 Previous-Sequence: The last message specification given.
225 Unseen-Sequence: Those messages not yet seen by the user.
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228 flist(1), mark(1), pick(1), mh-profile(5)
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231 None
232nmh-1.8 2013-10-17 MH-SEQUENCE(5)