setforward - Online in the Cloud

PROGRAM:

NAME

setforward - create a forwarding database

SYNOPSIS

setforward cdb tmp

DESCRIPTION

setforward reads a table of forwarding instructions from its standard input. It converts
the table into a forwarding database. The forwarding database can be used by fastforward.

setforward writes the forwarding database to tmp; it then moves tmp to cdb. tmp and cdb
must be on the same filesystem.

If there is a problem creating tmp, setforward complains and leaves cdb alone.

The forwarding database format is portable across machines.

INSTRUCTION FORMAT

A forwarding instruction contains a target, a colon, a series of commands, and a
semicolon. Each command is a recipient address, owner address, external mailing list, or
program. Commands are separated by commas.

For example,

root@yp.to: god@heaven.af.mil, staff@af.mil;

says that mail for root@yp.to should be forwarded to the recipient addresses
god@heaven.af.mil and staff@af.mil.

When setforward sees # it ignores all text from # to the end of the line:

# this is a comment

setforward ignores all other line endings, so you can split a forwarding instruction
across lines. It also ignores spaces and tabs. Exception: you can put a space (or tab or
comma or whatever) into a target or command by putting a backslash in front of it.
(However, NUL bytes are not permitted anywhere.)

TARGETS

When fastforward sees the incoming address user@host.dom, it tries three targets:
user@host.dom, @host.dom, and user@. It obeys the commands for the first target that it
finds. Target names are interpreted without regard to case.

All the commands for a single target must be listed in a single instruction. Exception:
an owner address can be listed in a separate instruction.

RECIPIENT ADDRESSES

If a command begins with an ampersand, setforward takes the remaining bytes in the command
as a recipient address:

boss@yp.to: &god@heaven.af.mil;

fastforward sends each incoming mail message to the recipient address. The recipient
address must include a fully qualified domain name. It cannot be longer than 800 bytes.

If a recipient address is itself a target in the forwarding table, fastforward will
recursively handle the instructions for that target. Note that @host.dom and user@
wildcards do not apply here; they apply only to the incoming address.

If a command begins with a letter or number, setforward takes the entire command as a
recipient address:

boss@yp.to: god@heaven.af.mil;

OWNER ADDRESSES

If a command begins with a question mark, setforward takes the remaining bytes in the
command as an owner address:

sos@heaven.af.mil: ?owner-sos@heaven.af.mil;

fastforward uses that address as the envelope sender for forwarded mail, so bounces will
go back to that address. (Normally, if a message is forwarded to a bad address, it will
bounce back to the original envelope sender.)

EXTERNAL MAILING LISTS

If a command begins with a dot or slash, setforward takes the entire command as the name
of a binary mailing list file created by setmaillist:

sos@heaven.af.mil: /etc/lists/sos.bin;

fastforward will read and obey the commands in that file. The file must be world-readable
and accessible to fastforward.

PROGRAMS

If a command begins with a vertical bar or exclamation point, setforward takes the rest of
the command as the name of a program to run:

dew@: |dew-monitor;

For a vertical bar, fastforward feeds the message to that program. An exclamation point
works the same way except that fastforward inserts $UFLINE, $RPLINE, and $DTLINE in front
of the message.

DUPLICATES

When fastforward is building the recipient list for a message, it keeps track of the
recipient addresses and external mailing lists it has used. If the same command shows up
again, it skips it. For example:

everybody@yp.to: programmers@yp.to, testers@yp.to;
programmers@yp.to: joe@yp.to, bob@yp.to;
testers@yp.to: joe@yp.to, fred@yp.to;

A message to everybody@yp.to will be sent to joe@yp.to only once. (This also means that
addresses in an internal forwarding loop are discarded.)

Exception: If a target has an owner address, commands for that target are considered
different from commands for ``outside'' targets.

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