NAME

       mh-alias - alias file for mh message system

DESCRIPTION

       This  describes  mh  personal alias files.  It does not describe aliases files used by the
       message transport system.

       Each line of the alias file has the format:

            alias : address-group
       or
            alias ; address-group
       or
            < alias-file
       or
            ; comment

       where:

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

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

       Continuation lines in alias files end with `\' followed by the newline character.

       `Alias-file' and `file' are UNIX file names.  UNIX-group is a group name (or number)  from
       /etc/group.   An address is a `simple' Internet-style address.  Throughout this file, case
       is ignored, except for file names.

       If the line starts with a `<', then 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 `<', then 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 `=', then the file /etc/group 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 `+', then the file /etc/group is consulted
       to determine the group-id of  the  UNIX-group  named  after  the  `+'.   Each  login  name
       occurring  in  the  /etc/passwd file whose group-id is indicated by this group is added to
       the address-list for the alias. I.e. only those  users  that  have  this  group  as  their
       initial login group are added.

       In  match,  a  trailing  `*' on an alias will match just about anything appropriate.  (See
       example below.)

       An approximation of the way aliases are resolved at posting time is (it's not really  done
       this way):

         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.   (This
            makes  replies  possible  since personal mh aliases are unknown to the mail transport
            system.)

       Since the alias file  is  read  line  by  line,  forward  references  work,  but  backward
       references are not recognized, thus, there is no recursion.

       Example Alias File:

            </etc/mmh/MoreAliases
            sgroup: fred, fear, freida
            b-people: Blind List: bill, betty
            fred: frated@UCI
            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/mmh/MoreAliases.  Following this, `fred' is defined as an alias for `frated@UCI', and
       `sgroup' is defined as an alias for the three names `frated@UCI', `fear', and `freida'.

       The  alias `b-people' is a blind list which includes the addresses `bill' and `betty'; the
       message will be delieved to those addresses, but the message header will  show only `Blind
       List: ;' (not the addresses).

       Next,  the definition of `UNIX-committee' is given by reading the file unix.aliases in the
       users mmh directory, `staff' is defined as all users who are  listed  as  members  of  the
       group  `staff' in the /etc/group file, and `wheels' is defined as all users whose group-id
       in /etc/passwd is equivalent to the `wheel' group.

       Finally, all aliases of the form `news.<anything>' are defined to be `news'.

       The key thing to understand about aliasing in mh is that aliases in  mh  alias  files  are
       expanded  into  the  headers  of  messages posted.  This aliasing occurs first, at posting
       time, without the knowledge of the  message  transport  system.   In  contrast,  once  the
       message  transport  system  is given a message to deliver to a list of addresses, for each
       address that appears to be local, a system-wide alias file is  consulted.   These  aliases
       are NOT expanded into the headers of messages delivered.

HELPFUL HINTS

       To use aliasing in mmh quickly, do the following:

         1) In  your  .mmh/profile, choose a name for your alias file, say `aliases', and add the
            line:

              Aliasfile: aliases

         2) Create the file `aliases' in your mmh directory.

         3) Start adding aliases to your `aliases' file as appropriate.

       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.

FILES

       None

PROFILE COMPONENTS

       Aliasfile:           For a default alias file

SEE ALSO

       ali(1), send(1), group(5), passwd(5), post(8)

CONTEXT

       None

HISTORY

       An  address group named `*', meaning everyone on the system, had been supported in nmh. It
       is not anymore in mmh.

BUGS

       Although the forward-referencing semantics of mh-alias files  prevent  recursion,  the  `<
       alias-file'  command may defeat this.  Since the number of file descriptors is finite (and
       very limited), such infinite recursion will terminate with a meaningless  diagnostic  when
       all the fds are used up.