4.3BSD-UWisc/man/catl/mh-alias.l
MH-ALIAS(5) UNIX Programmer's Manual MH-ALIAS(5)
NAME
mh-alias - alias file for MH message system
SYNOPSIS
any _M_H command
9 This describes both _M_H personal alias files and the (pri-
mary) alias file for mail delivery, the file
/usr/misc/mh/lib/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
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 /_e_t_c/_g_r_o_u_p. 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
/_e_t_c/_g_r_o_u_p 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.
9
Printed 1/10/87 MH 1
MH-ALIAS(5) UNIX Programmer's Manual MH-ALIAS(5)
In contrast, if the address-group starts with a `+', then
the file /_e_t_c/_g_r_o_u_p is consulted to determine the group-id
of the UNIX-group named after the `+'. Each login name
occurring in the /_e_t_c/_p_a_s_s_w_d 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
/_e_t_c/_p_a_s_s_w_d 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 _M_H
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/misc/mh/lib/BBoardAliases
sgroup: fred, fear, freida
fred: frated@UCI
UNIX-committee: <unix.aliases
staff: =staff
wheels: +wheel
everyone: *
news.*: news
Printed 1/10/87 MH 2
MH-ALIAS(5) UNIX Programmer's Manual MH-ALIAS(5)
The first line says that more aliases should immediately be
read from the file /_u_s_r/_m_i_s_c/_m_h/_l_i_b/_B_B_o_a_r_d_A_l_i_a_s_e_s. 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". Next, the definition of
"UNIX-committee" is given by reading the file _u_n_i_x._a_l_i_a_s_e_s
in the users _M_H directory, "staff" is defined as all users
who are listed as members of the group "staff" in the
/_e_t_c/_g_r_o_u_p file, and "wheels" is defined as all users whose
group-id in /_e_t_c/_p_a_s_s_w_d is equivalent to the "wheel" group.
Finally, "everyone" is defined as all users with a user-id
in /_e_t_c/_p_a_s_s_w_d greater than 200, and all aliases of the form
"news.<anything>" are defined to be "news".
The key thing to understand about aliasing in _M_H is that
aliases in _M_H 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 _M_H quickly, do the following:
First, in your ._m_h__p_r_o_f_i_l_e, choose a name for your pri-
mary alias file, say "aliases", and add three lines:
ali: -alias aliases
send: -alias aliases
whom: -alias ailases
Second, create the file "aliases" in your _M_H directory.
Third, start adding aliases to your "aliases" file as
appropriate.
FILES
/usr/misc/mh/lib/MailAliases Primary alias file
PROFILE COMPONENTS
None
SEE ALSO
ali(1), send(1), whom(1), group(5), passwd(5), conflict(8),
post(8)
DEFAULTS
None
Printed 1/10/87 MH 3
MH-ALIAS(5) UNIX Programmer's Manual MH-ALIAS(5)
CONTEXT
None
HISTORY
In previous releases of _M_H, only a single, system-wide
mh-alias file was supported. This led to a number of prob-
lems, 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 _M_H no
longer need to bother mail-system administrators for keeping
information in the system-wide alias file, as each _M_H user
can create/modify/remove aliases at will from any number of
personal files.
BUGS
Although the forward-referencing semantics of _m_h-_a_l_i_a_s 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.
Printed 1/10/87 MH 4