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.

nmh-1.6                                           Oct 14, 2012                                     MH-ALIAS(5mh)