NAME

       mh-alias - format of nmh alias files

DESCRIPTION

       Each line of an nmh alias file takes one of the following forms:

            alias : address-group

            alias ; address-group

            < alias-file

            ; | : | # comment

       where:

            address-group  := address-list
                           |  < file
                           |  = UNIX-group
                           |  + UNIX-group
                           |  *

            address-list   := address
                           |  address-list, address

       Continuation  lines  end  with  “\” followed by a newline character.  This also applies to
       comment lines.  Thus, the line following a “\”-terminated comment line is  a  continuation
       of that comment line.

       Alias-file  and  file  are UNIX file names.  UNIX-group is a group name or number from the
       system's group database.  Alias file contents are case-insensitive, with the exception  of
       filesystem path names.

       If  the  line  starts  with  a  “<”,  the  file named after the “<” is read for more alias
       definitions.  The reading is done recursively, so a “<” may occur in the beginning  of  an
       alias file with the expected results.

       If  the  address-group  starts  with  a  “<”, the file named after the “<” is read and its
       contents are added to the address-list for the alias.

       If the address-group starts with an “=”, the system's group database is consulted for  the
       UNIX-group  named  after  the  “=”.  Each login name occurring as a member of the group is
       added to the address-list for the alias.

       In contrast, if the address-group starts with  a  “+”,  the  system's  group  database  is
       consulted  to  determine  the  group-id of the UNIX-group named after the “+”.  Each login
       name occurring in the system's password database whose group-id is indicated by this group
       is added to the address-list for the alias.

       If  the  address-group  is simply “*”, the system's password database is consulted and all
       login names with a userid greater than some magic number (usually 200) are  added  to  the
       address-list  for  the alias.  This feature is obsolescent and will be removed in a future
       release.

       In match, a trailing “*” on an alias will match just about anything appropriate.

       An approximation of the way aliases are resolved at posting time is:

       1)     Build a list of all  addresses  from  the  message  to  be  delivered,  eliminating
              duplicate addresses.

       2)     If this draft originated on the local host, then for those addresses in the message
              that have no host specified, perform alias resolution.

       3)     For each line in the alias file,  compare  “alias”  against  all  of  the  existing
              addresses.   If  a match, remove the matched “alias” from the address list, and add
              each new address in the address-group to the address list if it is not  already  on
              the  list.   The  alias itself is not usually output, rather the address-group that
              the alias maps to is output instead.  If “alias” is terminated with a  “;”  instead
              of  a  “:”,  then both the “alias” and the address are output in the correct format
              (with the alias quoted if necessary and the address wrapped in <>).

       Since the mh-alias file is read line  by  line,  forward  references  work,  but  backward
       references are not recognized.

   Example Alias File
            </etc/nmh/BBoardAliases
            fred: frated@UCI.example
            sgroup: fred, fear, freida
            b-people: Blind List: bill, betty
            UNIX-committee: <unix.aliases
            staff: =staff
            wheels: +wheel
            news.*: news

       The  first  line  says  that  more  aliases  should  immediately  be  read  from  the file
       /etc/nmh/BBoardAliases.   Following  this,   “fred”   is   defined   as   an   alias   for
       “frated@UCI.example”,   and   “sgroup”  is  defined  as  an  alias  for  the  three  names
       “frated@UCI.example”, ”fear”, and ”freida”.

       The alias “b-people” is a blind list which includes the addresses “bill” and “betty”;  the
       message will be delivered to those addresses, but the message header will show only “Blind
       List: ;” (not the addresses).  The alias must  not  be  terminated  with,  or  contain,  a
       semicolon.   Note that blind lists are not supported with the sendmail/pipe mail transport
       method.

       Next, the definition of “UNIX-committee” is given by reading the file unix.aliases in  the
       user's  nmh  directory,  “staff”  is defined as all users who are listed as members of the
       group “staff” in the system's group database, and “wheels” is defined as all  users  whose
       group-id in the system's password database is equivalent to the “wheel” group.

PROFILE COMPONENTS

       Aliasfile:          Default alias file.

FILES

       /etc/nmh/MailAliases
                           System-wide default alias file.

SEE ALSO

       ali(1), send(1), whom(1), getgrent(3), getpwent(3), conflict(8), post(8)

BUGS

       Although  the  forward-referencing  semantics  of  mh-alias  files  prevent recursion, the
       alias-file directive may defeat this.  Since the number of  file  descriptors  is  finite,
       such  infinite recursion will terminate with a meaningless diagnostic when all the fds are
       used up.

       Earlier versions of this man page showed a semicolon at the end of the blind list example.
       That  caused the preceding alias to not be expanded.  There must not be a semicolon at the
       end of, or within, the address group of a blind list.  post will append the  semicolon  to
       the blind list name.