MH-ALIAS(5) [mh.6] MH-ALIAS(5)
NAME
mh-alias - alias file for MH message system
SYNOPSIS
any MH command
DESCRIPTION
This describes both MH personal alias files and the (pri-
mary) alias file for mail delivery, the file
/usr/contrib/mh/lib/MailAliases
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
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 alias-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.
MH April 22, 1986 1
MH-ALIAS(5) [mh.6] MH-ALIAS(5)
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 indi-
cated by this group is added to the address-list for the
alias.
If the address-group is simply `*', then the file
/etc/passwd 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.
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 post-
ing 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 MH aliases and personal aliases are
unknown to the mail transport system.)
Since the alias file is read line by line, forward refer-
ences work, but backward references are not recognized,
thus, there is no recursion.
Example:
</usr/contrib/mh/lib/BBoardAliases
sgroup: fred, fear, freida
fred: frated@UCI
UNIX-committee: <unix.aliases
staff: =staff
wheels: +wheel
everyone: *
news.*: news
The first line says that more aliases should immediately
be read from the file /usr/contrib/mh/lib/BBoardAliases.
MH April 22, 1986 2
MH-ALIAS(5) [mh.6] MH-ALIAS(5)
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. Next, the defi-
nition of UNIX-committee is given by reading the file
unix.aliases in the users MH 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, everyone is defined as all users with a
user-id in /etc/passwd greater than 200, and 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 sys-
tem. 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 MH quickly, do the following:
First, in your .mhprofile, choose a name for your
primary alias file, say aliases, and add three lines:
ali: -alias aliases
send: -alias aliases
whom: -alias ailases
Second, create the file aliases in your MH directory.
Third, start adding aliases to your aliases file as
appropriate.
FILES
/usr/contrib/mh/lib/MailAliases Primary alias file
PROFILE COMPONENTS
None
SEE ALSO
ali(1), send(1), whom(1), group(5), passwd(5), con-
flict(8), post(8)
DEFAULTS
None
CONTEXT
None
MH April 22, 1986 3
MH-ALIAS(5) [mh.6] MH-ALIAS(5)
HISTORY
In previous releases of MH, only a single, system-wide
mh-alias file was supported. This led to a number of
problems, since only mail-system administrators were capa-
ble of (un)defining aliases. Hence, the semantics of
mh-alias were extended to support personal alias files.
Users of MH no longer need to bother mail-system adminis-
trators for keeping information in the system-wide alias
file, as each MH user can create/modify/remove aliases at
will from any number of personal files.
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.
MH April 22, 1986 4