MH-ALIAS(5)                   File Formats Manual                  MH-ALIAS(5)



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
            </usr/local/lib/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 /usr/local/lib/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
       /usr/local/lib/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(5)
