MH-ALIAS(5) [nmh-1.0.4] (MH.6.8) MH-ALIAS(5)
NAME
mh-alias - alias file for nmh message system
SYNOPSIS
any nmh command
DESCRIPTION
This describes both nmh personal alias files and the global
alias file for nmh mail delivery, the file
/usr/freeware/lib/nmh/etc/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
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.
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MH-ALIAS(5) [nmh-1.0.4] (MH.6.8) MH-ALIAS(5)
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.
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
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 nmh aliases and
personal 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.
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MH-ALIAS(5) [nmh-1.0.4] (MH.6.8) MH-ALIAS(5)
Example:
</usr/freeware/lib/nmh/etc/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/freeware/lib/nmh/etc/BBoardAliases.
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 nmh 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 nmh is that
aliases in nmh 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 nmh 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 nmh directory.
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MH-ALIAS(5) [nmh-1.0.4] (MH.6.8) MH-ALIAS(5)
Third, start adding aliases to your aliases file as
appropriate.
FILES
/usr/freeware/lib/nmh/etc/MailAliasesglobal nmh 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
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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