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.TH ALIASES 8
.tr ~
.SH NAME
aliases \- alias file for smail
.SH DESCRIPTION
This file is used by
.I smail
only if
.I SENDMAIL
is
.I not defined.
If
.I SENDMAIL
is defined, then
.I sendmail
does all of the aliasing for the host.
.PP
This file contains a list of aliases for
local users or mailing lists.
The format of each alias is
.sp
.ce
alias_name~recip_name1~recip_name2~...
.sp
An attempt has been made to remain compatible with
.I sendmail
alias file format, though the syntax is much more format free than
.I sendmail.
As distributed,
.I case differences are ignored
when comparing names to aliases.
Only alias names which resolve to the local host are recognized, and are
stored in their local form.
Lines which start with a white~space are continuation lines.
Parenthesised strings are taken as comments (no nesting),
as is anything after a '#' (as in
.IR /bin/sh ).
Here are some examples:
.sp
.nf
# this whole line is a comment
#
# These are equivalent definitions

alias_name      recip1 recip2 recip3

alias_name:     recip1, recip2 , recip3

alias_name      recip1 recip2
                recip3

alias_name      recip1  # Recip1's name
                recip2  # Recip2's name
                recip3  # Recip3's name

alias_name      recip1 (Recp1's name) recip2 (Recp2's name)
                recip3 (Recp3's name)

alias_name@thishost     recip1 recip2 recip3

alias_name@thisdomain   recip1 recip2 recip3

thishost!alias_name     recip1 recip2 recip3

thisdomain!alias_name   recip1 recip2 recip3
.fi
.PP
Mailing lists are easily handled by two forms of file inclusion.
The first form is the same as is supported by
.I sendmail
.sp
.ce
mylist	:include:/usr/lib/ml/mylist
.sp
In this example, each entry in
.I /usr/lib/ml/mylist
would be added to the alias for
.I mylist.
The second form is unique to
.I smail.
It allows the
.I aliases
file to include other
.I aliases
files.
.sp
.ce
:include:/usr/lib/ml/more-aliases
.sp
This would include the file
.I /usr/lib/ml/more-aliases
as a regular alias file.
This makes it easier to maintain groups of aliases that
change frequently, such as the list of netnews moderators.
.PP
All aliases are recursive, so care
must be taken in their definition.
.I smail
aliasing attempts to prevent infinite loops, and to
do what was intended by the user.  For example, the alias:
.sp
.ce
mylogin~mypc!mylogin~mylogin
.sp
Expands to
.sp
.ce
mypc!mylogin mylogin
.sp
even though the second occurrence of
.I mylogin
matches the alias name.
.sp
Both forms of file inclusion are recursive, too,
so watch out for nesting include files.  They
may lead to infinite loops.
.PP
While the cost of parsing an alias file is usually negligible,
it's wise to take savings anywhere savings
can be found.  Therefore, it's worth mentioning
.IR smail 's
parsing strategy.
.I smail
will try to get by with doing as little work
as possible when aliasing.  If on a particular
invocation of
.I smail,
none of the recipent addresses are local,
(i.e., not potential aliases)
then the
.I aliases
file won't even be read.  Similarly,
when an
.I aliases
file is read, it does not expand any of the :include: files
until they are referenced.  Thus, in the alias (above) for
.I mylist,
the file
.I :include:/usr/lib/ml/mylist
would not be opened and read (parsed) unless
mail was sent to
.I mylist.
Wise use of :include: files can greatly
increase the efficiency of the alias utility.
It's not clear exactly where the
.I break-even
point is when deciding to use an  :include: file in an alias,
versus having all of the recipents listed on the line;
but if a mailing list is large (whatever that means)
it is wise to use the :include: feature to save on
parsing costs.  Note that this discussion only applies to the
first form of file inclusion, since reading an
.I aliases
file constitutes a reference to :include: files of the second form.
.PP
There is another form of aliasing which works with the alias capability.
This is called
.I per user forwarding.
For a given user name, if there is no alias for the user
then, if the file
.I ~user/.forward
exists, then its contents will be treated as an alias for
the user.  The syntax is the same as that of the
recipient lists in the alias file described above.
.PP
One difference between
.I smail
and
.I sendmail
is that
.I smail
doesn't handle stuff like mail to files
or command execution.
.SH SEE ALSO
smail(8), paths(8), pathproc(8)
.SH VERSION
@(#)aliases.8	2.2 smail 1/28/87