aliases -- System Administration

File of users' aliases
/usr/lib/mail/aliases

File /usr/lib/mail/aliases holds  aliases for users' addresses -- either on
your system, or  on other systems.  The command smail  reads this file when
it figures out how to deliver a mail message.

An alias is a ``nickname'' for  a user.  Once you have established an alias
for a user, you can use that alias to send mail to her; this spares you the
trouble of  typing that person's  convoluted e-mail address.   An alias can
also name an  entire group of users; when you  use the alias to send a mail
message, every person in the group receives a copy.

The format of each alias is

     alias_name:    target

where alias_name gives the alias to which you mail your message, and target
is name to which where smail actually directs the message.  target can be a
login identifier on your local system;  a mail address of a user on another
system; or a cluster of users either on your system or on remote systems.

For    example,   consider    the    user   whose    e-mail   address    is
ivan@lepanto.mwc.com. If you add the entry

    ivan:   ivan@lepanto.mwc.com

to file  /usr/lib/mail/aliases, then  whenever you  send mail to  ivan, the
routing program  smail will automatically ``expand''  the address from ivan
to ivan@lepanto.mwc.com,  and dispatch  the message properly.   This spares
you needless work, and eliminates the  errors that would occur if you typed
long addresses by hand.

Please note that smail ignores differences  in case when it compares a name
with  an alias.   If  a line  begins  with a  white-space character,  smail
assumes  that that  line is  a  continuation of  the previous  line.  smail
ignores strings within parentheses, as  well as any text that appears after
the  pound sign  `#'.  Thus,  you  can use  `#' to  embed a  comment within
aliases.

Examples

The following gives an example form of aliases:

     # this whole line is a comment

     # "mail programmers" sends mail to local users joe, jack, and bill
     programmers:   joe jack bill

     # same as above
     programmers:   joe jack
                    bill

     # same as above
     programmers    joe jack
                    bill

     # same as above
     programmers    joe   # Joe Smith
                    jack  # Jack Thomas
                    bill  # Bill Williams

     # and yet another way; note use of parentheses to comment text
     programmers    joe (Joe Smith) jack (Jack Thomas)
                    bill (Bill Williams)

     # send a message to someone on another system.
     # this uses ``bang-path'' addressing
     joe:           boston!widget!js

     # send a message to users on both your and another system
     programmers:   boston!widget!js   # Joe Smith
                    chicago!gadget!jt  # Jack Thomas
                    bill               # Bill Williams

     # all members of "programmers" group work at site "widget"
     programmers!widget  joe jack bill

To tell smail  to use the contents of another  file to expand an alias, use
the following form:

     fredlist       :include:/usr/lib/mail/fredlist

smail adds each entry in /usr/lib/mail/fredlist to the alias for fredlist.

You  can also  tell  smail to  read  another alias  file,  and include  its
contents in the list of aliases to be expanded.  For example, the following
instruction

    :include:/usr/lib/mail/morealiases

when embedded within /usr/lib/mail/aliases, tells smail to add the contents
of /usr/lib/mail/morealiases to those of /usr/lib/mail/aliases as a regular
alias file.

All aliases  are recursive, so  you must be  careful when you  define them.
For example, the entries

     bill:     joe
     joe:      bill

causes an  infinite loop.  smail attempts to detect  infinite loops, and to
guess what  you intended to do.  The following  example illustrates how you
can use  an alias to deliver  mail to a remote  user as well as  to a local
user who has the same name  as the alias being expanded.  smail expands the
alias

     mylogin:       mypc!mylogin  mylogin

to

    mypc!mylogin mylogin

even though the second occurrence of mylogin matches the alias name.

Both forms of  file inclusion are recursive, too, and  may lead to infinite
loops if handled carelessly.

See Also

Administering COHERENT,
mail [overview],
smail

Notes

Beginning with release 4.2.14 of  COHERENT, smail's aliases are kept in the
form of a DBM data base.  This is a simple data base that uses a hash table
to speed the retrieval of information.  If you change your file of aliases,
you must invoke  either the command newaliases or the  command smail -bi to
rebuild the  binary data base of  aliases.  For details on  what a DBM data
base  is, see  the Lexicon  entry for  libgdbm. For details  on how  to use
newaliases or smail, see their respective entries in the Lexicon.

© 2012 by Stephen A. Ness