1MH-ALIAS(5) [nmh-1.3] MH-ALIAS(5)
2
6 mh-alias - alias file for nmh message system
7
9 any nmh command
10
12 This describes both nmh personal alias files and the global alias file
13 for nmh mail delivery, the file
14 /etc/nmh/MailAliases
16 It does not describe aliases files used by the message transport sys‐
18 tem. Each line of the alias file has the format:
19 alias : address-group
21 or
22 alias ; address-group
23 or
24 < alias-file
25 or
26 ; comment
27 where:
29 address-group := address-list
31 | < file
32 | = UNIX-group
33 | + UNIX-group
34 | *
35 address-list := address
37 | address-list, address
38 Continuation lines in alias files end with `\' followed by the newline
40 character.
41 “Alias-file” and “file” are UNIX file names. UNIX-group is a group
43 name (or number) from /etc/group. An address is a “simple” Inter‐
44 net-style address. Througout this file, case is ignored, except for
45 file names.
46 If the line starts with a `<', then the file named after the `<' is
48 read for more alias definitions. The reading is done recursively, so a
49 `<' may occur in the beginning of an alias file with the expected
50 results.
51 If the address-group starts with a `<', then the file named after the
53 `<' is read and its contents are added to the address-list for the
54 alias.
55 If the address-group starts with an `=', then the file /etc/group is
57 consulted for the UNIX-group named after the `='. Each login name
58 occurring as a member of the group is added to the address-list for the
59 alias.
60 In contrast, if the address-group starts with a `+', then the file
62 /etc/group is consulted to determine the group-id of the UNIX-group
63 named after the `+'. Each login name occurring in the /etc/passwd file
64 whose group-id is indicated by this group is added to the address-list
65 for the alias.
66 If the address-group is simply `*', then the file /etc/passwd is con‐
68 sulted and all login names with a userid greater than some magic number
69 (usually 200) are added to the address-list for the alias.
70 In match, a trailing “*” on an alias will match just about anything
72 appropriate. (See example below.)
73 An approximation of the way aliases are resolved at posting time is
75 (it's not really done this way):
76 1) Build a list of all addresses from the message to be delivered,
78 eliminating duplicate addresses.
79 2) If this draft originated on the local host, then for those
81 addresses in the message that have no host specified, perform
82 alias resolution.
83 3) For each line in the alias file, compare “alias” against all of
85 the existing addresses. If a match, remove the matched “alias”
86 from the address list, and add each new address in the
87 address-group to the address list if it is not already on the
88 list. The alias itself is not usually output, rather the
89 address-group that the alias maps to is output instead. If
90 “alias” is terminated with a `;' instead of a `:', then both the
91 “alias” and the address are output in the correct format. (This
92 makes replies possible since nmh aliases and personal aliases are
93 unknown to the mail transport system.)
94 Since the alias file is read line by line, forward references work, but
96 backward references are not recognized, thus, there is no recursion.
97 Example Alias File:
99 </etc/nmh/BBoardAliases
101 sgroup: fred, fear, freida
102 b-people: Blind List: bill, betty;
103 fred: frated@UCI
104 UNIX-committee: <unix.aliases
105 staff: =staff
106 wheels: +wheel
107 everyone: *
108 news.*: news
109 The first line says that more aliases should immediately be read from
111 the file /etc/nmh/BBoardAliases. Following this, “fred” is defined as
112 an alias for “frated@UCI”, and “sgroup” is defined as an alias for the
113 three names “frated@UCI”, ”fear”, and ”freida”.
114 The alias “b-people” is a blind list which includes the addresses
116 “bill” and “betty”; the message will be delieved to those addresses,
117 but the message header will show only “Blind List: ;” (not the
118 addresses).
119 Next, the definition of “UNIX-committee” is given by reading the file
121 unix.aliases in the users nmh directory, “staff” is defined as all
122 users who are listed as members of the group “staff” in the /etc/group
123 file, and “wheels” is defined as all users whose group-id in
124 /etc/passwd is equivalent to the “wheel” group.
125 Finally, “everyone” is defined as all users with a user-id in
127 /etc/passwd greater than 200, and all aliases of the form “news.<any‐
128 thing>” are defined to be “news”.
129 The key thing to understand about aliasing in nmh is that aliases in
131 nmh alias files are expanded into the headers of messages posted. This
132 aliasing occurs first, at posting time, without the knowledge of the
133 message transport system. In contrast, once the message transport sys‐
134 tem is given a message to deliver to a list of addresses, for each
135 address that appears to be local, a system-wide alias file is con‐
136 sulted. These aliases are NOT expanded into the headers of messages
137 delivered.
138
141 To use aliasing in nmh quickly, do the following:
142 1) In your .mh_profile, choose a name for your alias file, say
144 “aliases”, and add the line:
145 Aliasfile: aliases
147 2) Create the file “aliases” in your nmh directory.
149 3) Start adding aliases to your “aliases” file as appropriate.
151
154 /etc/nmh/MailAliases global nmh alias file
155
158 Aliasfile: For a default alias file
159
162 ali(1), send(1), whom(1), group(5), passwd(5), conflict(8), post(8)
163
166 None
167
170 Although the forward-referencing semantics of mh-alias files prevent
171 recursion, the “< alias-file” command may defeat this. Since the num‐
172 ber of file descriptors is finite (and very limited), such infinite
173 recursion will terminate with a meaningless diagnostic when all the fds
174 are used up.
175 Forward references do not work correctly inside blind lists.
177MH.6.8 1 June 2008 MH-ALIAS(5)