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   1 .TH MH-ALIAS %manext5% 2014-04-18 "%nmhversion%"
   2 .
   3 .\" %nmhwarning%
   4 .
   5 .SH NAME
   6 mh-alias \- format of nmh alias files
   7 .SH DESCRIPTION
   8 .PP
   9 Each line of an
  10 .B nmh
  11 alias file takes one of the following forms:
  12 .PP
  13 .RS 5
  14 .I alias
  15 .B :
  16 .I address-group
  17 .RE
  18 .sp
  19 .RS 5
  20 .I alias
  21 .B ;
  22 .I address-group
  23 .RE
  24 .sp
  25 .RS 5
  26 .B <
  27 .I alias-file
  28 .RE
  29 .sp
  30 .RS 5
  31 .B ;
  32 |
  33 .B :
  34 |
  35 .B #
  36 .I comment
  37 .RE
  38 .PP
  39 where:
  40 .PP
  41 .RS 5
  42 .nf
  43 .IR address-group "     := " address-list
  44 .RI "                   |  < " file
  45 .RI "                   |  = " Unix-group
  46 .RI "                   |  + " Unix-group
  47
  48 .IR address-list "      := " address
  49 .RI "                   |  " address-list ", " address
  50 .fi
  51 .RE
  52 .PP
  53 Continuation lines end with \*(lq\\\*(rq followed by a newline
  54 character.  This also applies to comment lines.  Thus, the line following a
  55 \*(lq\\\*(rq-terminated
  56 comment line is a continuation of
  57 that comment line.
  58 .PP
  59 .I Alias-file
  60 and
  61 .I file
  62 are Unix file names.
  63 .I Unix-group
  64 is a group name or number from
  65 the system's group database.
  66 Alias file contents are case-insensitive, with the exception
  67 of filesystem path names.
  68 .PP
  69 If the line starts with a \*(lq<\*(rq, the file named after the \*(lq<\*(rq is
  70 read for more alias definitions.  The reading is done recursively, so a
  71 \*(lq<\*(rq may occur in the beginning of an alias file with the expected results.
  72 .PP
  73 If the
  74 .I address-group
  75 starts with a \*(lq<\*(rq, the file named after the
  76 \*(lq<\*(rq is read and its contents are added to the
  77 .I address-list
  78 for the alias.
  79 .PP
  80 If the
  81 .I address-group
  82 starts with an \*(lq=\*(rq, the
  83 system's group database
  84 is consulted for the Unix-group named after the \*(lq=\*(rq.  Each login name
  85 occurring as a member of the group is added to the
  86 .I address-list
  87 for the alias.
  88 .PP
  89 In contrast, if the
  90 .I address-group
  91 starts with a \*(lq+\*(rq, the system's group database
  92 is consulted to determine the group-id of the
  93 Unix-group named after the \*(lq+\*(rq.  Each login name occurring in the
  94 system's password database
  95 whose group-id is indicated by this group is
  96 added to the
  97 .I address-list
  98 for the alias.
  99 .PP
 100 In match, a trailing \*(lq*\*(rq on an alias will match just about anything
 101 appropriate.
 102 .PP
 103 An approximation of the way aliases are resolved at posting time is:
 104 .IP 1)
 105 Build a list of all addresses from the message to be delivered,
 106 eliminating duplicate addresses.
 107 .IP 2)
 108 For those addresses in the message that have no host specified,
 109 perform alias resolution.
 110 .IP 3)
 111 For each line in the alias file, compare \*(lqalias\*(rq against all of
 112 the existing addresses.  If a match, remove the matched \*(lqalias\*(rq
 113 from the address list, and add each new address in the address-group to
 114 the address list if it is not already on the list.  The alias itself is
 115 not usually output, rather the address-group that the alias maps to is
 116 output instead.  If \*(lqalias\*(rq is terminated with a \*(lq;\*(rq instead of
 117 a \*(lq:\*(rq, then both the \*(lqalias\*(rq and the address are output in the
 118 correct format (with the alias quoted if necessary and the address
 119 wrapped in <>).
 120 .PP
 121 Since the
 122 .I mh-alias
 123 file is read line by line, forward references work, but
 124 backward references are not recognized.
 125 .SS
 126 Example Alias File
 127 .PP
 128 .RS 5
 129 .nf
 130 <%nmhetcdir%/BBoardAliases
 131 sgroup: fred, fear, freida
 132 fred: frated@UCI.example
 133 b-people: Blind List: bill, betty
 134 Unix\-committee: <unix.aliases
 135 staff: =staff
 136 wheels: +wheel
 137 news.*: news
 138 .fi
 139 .RE
 140 .PP
 141 The first line says that more aliases should immediately be read from
 142 the file
 143 .BR %nmhetcdir%/BBoardAliases .
 144 Next, \*(lqsgroup\*(rq is defined as an alias for three names,
 145 and one of them, \*(lqfred\*(rq,
 146 is a forward reference to another alias for \*(lqfrated@UCI.example\*(rq.
 147 .PP
 148 The alias \*(lqb-people\*(rq is a blind list which includes the addresses
 149 \*(lqbill\*(rq and \*(lqbetty\*(rq; the message will be delivered to those
 150 addresses, but the message header will show only \*(lqBlind List: ;\*(rq
 151 (not the addresses).  The alias must not be terminated with, or contain,
 152 a semicolon.
 153 Note that blind lists are not supported with the
 154 .B sendmail/pipe
 155 mail transport method.
 156 .PP
 157 The definition of \*(lqUnix\-committee\*(rq is given by
 158 reading the file
 159 .I unix.aliases
 160 in the user's
 161 .B nmh
 162 directory.
 163 .PP
 164 \*(lqstaff\*(rq is defined as all users who are listed as members of the
 165 group \*(lqstaff\*(rq in the
 166 system's group database, and \*(lqwheels\*(rq
 167 is defined as all users whose group-id in
 168 the system's password database
 169 is equivalent to the \*(lqwheel\*(rq group.
 170 .PP
 171 Lastly,
 172 .RI \*(lqnews. anything \*(rq
 173 is aliased to \*(lqnews\*(rq;
 174 the full stop is just another literal character.
 175 .SH "PROFILE COMPONENTS"
 176 .TP 20
 177 Aliasfile:
 178 Default alias file.
 179 .SH FILES
 180 .TP 20
 181 %nmhetcdir%/MailAliases
 182 System-wide default alias file.
 183 .SH "SEE ALSO"
 184 .IR ali (1),
 185 .IR send (1),
 186 .IR whom (1),
 187 .IR getgrent (3),
 188 .IR getpwent (3),
 189 .IR post (8)
 190 .SH BUGS
 191 Although the forward-referencing semantics of
 192 mh\-alias
 193 files prevent recursion, the
 194 .B alias-file
 195 directive may defeat this.
 196 Since the number of file descriptors is finite, such
 197 infinite recursion will terminate with a meaningless diagnostic when
 198 all the fds are used up.
 199 .PP
 200 Earlier versions of this man page showed a semicolon at the end of the
 201 blind list example.  That caused the preceding alias to not be
 202 expanded.  There must not be a semicolon at the end of, or within, the
 203 address group of a blind list.
 204 .B post
 205 will append the semicolon to the blind list name.