MH-ALIAS(5) Headers, Tables, and Macros 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/local/lib/mh/MailAliases
It does not describe aliases files used by the message tran-
sport 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 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
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MH-ALIAS(5) Headers, Tables, and Macros MH-ALIAS(5)
/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 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 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 speci-
fied, 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.
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MH-ALIAS(5) Headers, Tables, and Macros MH-ALIAS(5)
Example:
</usr/local/lib/mh/BBoardAliases
sgroup: fred, fear, freida
b-people: Blind List: bill, betty;
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/local/lib/mh/BBoardAliases. Follow-
ing 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 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 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 con-
sulted. 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 .mh_profile, choose a name for your
alias file, say "aliases", and add the line:
Aliasfile: aliases
Second, create the file "aliases" in your MH directory.
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MH-ALIAS(5) Headers, Tables, and Macros MH-ALIAS(5)
Third, start adding aliases to your "aliases" file as
appropriate.
FILES
/usr/local/lib/mh/MailAliases Primary alias file
PROFILE COMPONENTS
Aliasfile: For a default alias file
SEE ALSO
ali(1), send(1), whom(1), group(5), passwd(5), conflict(8),
post(8)
DEFAULTS
None
CONTEXT
None
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 capable 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 administrators 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.
Forward references do not work correctly inside blind lists.
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