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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 email-address 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
  46 .IR address-list "      := " address
  47 .RI "                   |  " address-list ", " address
  48 .fi
  49 .RE
  50 .PP
  51 Continuation lines end with \*(lq\\\*(rq followed by a newline
  52 character.  This also applies to comment lines.  Thus, the line following a
  53 \*(lq\\\*(rq-terminated
  54 comment line is a continuation of
  55 that comment line.
  56 .PP
  57 .I Alias-file
  58 and
  59 .I file
  60 are Unix file names.
  61 Alias file contents are case-insensitive, with the exception
  62 of filesystem path names.
  63 .PP
  64 If the line starts with a \*(lq<\*(rq, the file named after the \*(lq<\*(rq is
  65 read for more alias definitions.  The reading is done recursively, so a
  66 \*(lq<\*(rq may occur in the beginning of an alias file with the expected results.
  67 .PP
  68 If the
  69 .I address-group
  70 starts with a \*(lq<\*(rq, the file named after the
  71 \*(lq<\*(rq is read and its contents are added to the
  72 .I address-list
  73 for the alias.
  74 .PP
  75 In match, a trailing \*(lq*\*(rq on an alias will match just about anything
  76 appropriate.
  77 .PP
  78 An approximation of the way aliases are resolved at posting time is:
  79 .IP 1)
  80 Build a list of all addresses from the message to be delivered,
  81 eliminating duplicate addresses.
  82 .IP 2)
  83 For those addresses in the message that have no host specified,
  84 perform alias resolution.
  85 .IP 3)
  86 For each line in the alias file, compare \*(lqalias\*(rq against all of
  87 the existing addresses.  If a match, remove the matched \*(lqalias\*(rq
  88 from the address list, and add each new address in the address-group to
  89 the address list if it is not already on the list.  The alias itself is
  90 not usually output, rather the address-group that the alias maps to is
  91 output instead.  If \*(lqalias\*(rq is terminated with a \*(lq;\*(rq instead of
  92 a \*(lq:\*(rq, then both the \*(lqalias\*(rq and the address are output in the
  93 correct format (with the alias quoted if necessary and the address
  94 wrapped in <>).
  95 .PP
  96 Since the
  97 .I mh-alias
  98 file is read line by line, forward references work, but
  99 backward references are not recognized.
 100 .SS
 101 Example Alias File
 102 .PP
 103 .RS 5
 104 .nf
 105 <%nmhetcdir%/BBoardAliases
 106 sgroup: fred, fear, freida
 107 fred: frated@UCI.example
 108 b-people: Blind List: bill, betty
 109 Unix\-committee: <unix.aliases
 110 news.*: news
 111 .fi
 112 .RE
 113 .PP
 114 The first line says that more aliases should immediately be read from
 115 the file
 116 .BR %nmhetcdir%/BBoardAliases .
 117 Next, \*(lqsgroup\*(rq is defined as an alias for three names,
 118 and one of them, \*(lqfred\*(rq,
 119 is a forward reference to another alias for \*(lqfrated@UCI.example\*(rq.
 120 .PP
 121 The alias \*(lqb-people\*(rq is a blind list which includes the addresses
 122 \*(lqbill\*(rq and \*(lqbetty\*(rq; the message will be delivered to those
 123 addresses, but the message header will show only \*(lqBlind List: ;\*(rq
 124 (not the addresses).  The alias must not be terminated with, or contain,
 125 a semicolon.
 126 Note that blind lists are not supported with the
 127 .B sendmail/pipe
 128 mail transport method.
 129 .PP
 130 The definition of \*(lqUnix\-committee\*(rq is given by
 131 reading the file
 132 .I unix.aliases
 133 in the user's
 134 .B nmh
 135 directory.
 136 .PP
 137 Lastly,
 138 .RI \*(lqnews. anything \*(rq
 139 is aliased to \*(lqnews\*(rq;
 140 the full stop is just another literal character.
 141 .SH "PROFILE COMPONENTS"
 142 .TP 20
 143 Aliasfile:
 144 Default alias file.
 145 .SH FILES
 146 .TP 20
 147 %nmhetcdir%/MailAliases
 148 System-wide default alias file.
 149 .SH "SEE ALSO"
 150 .IR ali (1),
 151 .IR send (1),
 152 .IR whom (1),
 153 .IR getgrent (3),
 154 .IR getpwent (3),
 155 .IR post (8)
 156 .SH BUGS
 157 Although the forward-referencing semantics of
 158 mh\-alias
 159 files prevent recursion, the
 160 .B alias-file
 161 directive may defeat this.
 162 Since the number of file descriptors is finite, such
 163 infinite recursion will terminate with a meaningless diagnostic when
 164 all the fds are used up.
 165 .PP
 166 Earlier versions of this man page showed a semicolon at the end of the
 167 blind list example.  That caused the preceding alias to not be
 168 expanded.  There must not be a semicolon at the end of, or within, the
 169 address group of a blind list.
 170 .B post
 171 will append the semicolon to the blind list name.