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
/etc/nmh/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 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.
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.
Example Alias File:
</etc/nmh/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
/etc/nmh/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:
- 1)
- In your .mhprofile, choose a name for your alias
file, say “aliases”, and add the line:
- 2)
- Create the file “aliases” in your
nmh directory.
- 3)
- Start adding aliases to your “aliases”
file as appropriate.
FILES¶
^/etc/nmh/MailAliases~^global 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)
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.
