bionic (5) mh-alias.5mh.gz

Provided by: mmh_0.3-3_amd64 bug

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.  Througout 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.

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.

       Forward references do not work correctly inside blind lists.