slocal(1) - man - phpman

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SLOCAL(1mh) SLOCAL(1mh)

NAME
slocal - asynchronously filter and deliver new mail to nmh

SYNOPSIS
/usr/lib/mh/slocal [-help] [-version] [-addr address] [-info data] [-sender sender] [-user
username] [-mailbox mbox] [-file file] [-maildelivery deliveryfile] [-verbose | -nover‐‐
bose] [-suppressdup | -nosuppressdup] [-debug]

DESCRIPTION
slocal is a program designed to allow you to have your inbound mail processed according to a
complex set of selection criteria. You do not normally invoke slocal yourself, rather slocal
is invoked on your behalf by your system's Message Transfer Agent (such as sendmail) when the
message arrives.

The message selection criteria used by slocal is specified in the file “.maildelivery” in the
user's home directory. You can specify an alternate file with the -maildelivery file option.
The syntax of this file is specified below.

The message delivery address and message sender are determined from the Message Transfer
Agent envelope information, if possible. Under sendmail, the sender will obtained from the
UUCP “From:” line, if present. The user may override these values with the -addr and -sender
switches.

The message is normally read from the standard input. The -file switch sets the name of the
file from which the message should be read, instead of reading stdin. This is useful when
debugging a “.maildelivery” file.

The -user switch tells slocal the name of the user for whom it is delivering mail. It must
exist on the local system. The -mailbox switch tells slocal the name of the user's mail drop
file.

slocal is able to detect and suppress duplicate messages. To enable this, use the option
-suppressdup. slocal will keep a database containing the Message-ID's of incoming messages,
in order to detect duplicates. Depending on your configuration, this database will be in ei‐
ther ndbm or Berkeley db format.

The -info switch may be used to pass an arbitrary argument to sub-processes which slocal may
invoke on your behalf.

The -verbose switch causes slocal to give information on stdout about its progress. The -de‐‐
bug switch produces more verbose debugging output on stderr. These flags are useful when
creating and debugging your “.maildelivery” file, as they allow you to see the decisions and
actions that slocal is taking, as well as check for syntax errors in your “.maildelivery”
file.

Message Transfer Agents
Most modern MTAs including sendmail, postfix and exim support a .forward file for directing
incoming mail. You should include the line

“| /usr/lib/mh/slocal -user username”

in your .forward file in your home directory. This will cause your MTA to invoke slocal on
your behalf when a message arrives.

The Maildelivery File
The “.maildelivery” file controls how slocal filters and delivers incoming mail. Each line
of this file consists of five fields, separated by whitespace or comma. Since double-quotes
are honored, these characters may be included in a single argument by enclosing the entire
argument in double-quotes. A double-quote can be included by preceding it with a backslash.
Lines beginning with `#' and blank lines are ignored.

The format of each line in the “.maildelivery” file is:

header pattern action result string

header:
The name of a header field (such as To, Cc, or From) that is to be searched for a pat‐
tern. This is any field in the headers of the message that might be present.

The following special fields are also defined:

source the out-of-band sender information

addr the address that was used to cause delivery to the recipient

default this matches only if the message hasn't been delivered yet

* this always matches

pattern:
The sequence of characters to match in the specified header field. Matching is case-in‐
sensitive, but does not use regular expressions.

action:
The action to take to deliver the message. When a message is delivered, a “Deliv‐
ery-Date: date” header is added which indicates the date and time that message was de‐
livered.

destroy
This action always succeeds.

file, mbox, or >
Append the message to the file named by string. The message is appended to the file
in mbox (uucp) format. This is the format used by most other mail clients (such as
mailx, elm). If the message can be appended to the file, then this action succeeds.

mmdf
Identical to file, but always appends the message using the MMDF mailbox format.

pipe or |
Pipe the message as the standard input to the command named by string, using the
Bourne shell sh to interpret the string. Prior to giving the string to the shell,
it is expanded with the following built-in variables:

$(sender) the out-of-band sender information

$(address) the address that was used to cause delivery to the recipient

$(size) the size of the message in bytes

$(reply-to) either the “Reply-To:” or “From:” field of the message

$(info) the out-of-band information specified

qpipe or ^
Similar to pipe, but executes the command directly, after built-in variable expan‐
sion, without assistance from the shell. This action can be used to avoid quoting
special characters which your shell might interpret.

folder or +
Store the message in the nmh folder named by string. Currently this is handled by
piping the message to the nmh program rcvstore, although this may change in the fu‐
ture.

result:
Indicates how the action should be performed:

A Perform the action. If the action succeeds, then the message is considered deliv‐
ered.

R Perform the action. Regardless of the outcome of the action, the message is not
considered delivered.

? Perform the action only if the message has not been delivered. If the action suc‐
ceeds, then the message is considered delivered.

N Perform the action only if the message has not been delivered and the previous ac‐
tion succeeded. If this action succeeds, then the message is considered delivered.

The delivery file is always read completely, so that several matches can be made and
several actions can be taken.

Security of Delivery Files
In order to prevent security problems, the “.maildelivery” file must be owned either by the
user or by root, and must be writable only by the owner. If this is not the case, the file
is not read.

If the “.maildelivery” file cannot be found, or does not perform an action which delivers the
message, then slocal will check for a global delivery file at /etc/nmh/maildelivery. This
file is read according to the same rules. This file must be owned by root and must be
writable only by root.

If a global delivery file cannot be found or does not perform an action which delivers the
message, then standard delivery to the user's mail drop is performed.

Example Delivery File
To summarize, here's an example delivery file:

#
# .maildelivery file for nmh's slocal
#
# Blank lines and lines beginning with a '#' are ignored
#
# FIELD PATTERN ACTION RESULT STRING
#

# File mail with foobar in the “To:” line into file foobar.log
To foobar file A foobar.log

# Pipe messages from coleman to the program message-archive
From coleman pipe A /bin/message-archive

# Anything to the “nmh-workers” mailing list is put in
# its own folder, if not filed already
To nmh-workers folder ? nmh-workers

# Anything with Unix in the subject is put into
# the file unix-mail
Subject unix file A unix-mail

# I don't want to read mail from Steve, so destroy it
From steve destroy A -

# Put anything not matched yet into mailbox
default - file ? mailbox

# always run rcvtty
* - pipe R /usr/lib/mh/rcvtty

Sub-process environment
When a process is invoked, its environment is: the user/group-ids are set to recipient's ids;
the working directory is the recipient's home directory; the umask is 0077; the process has
no /dev/tty; the standard input is set to the message; the standard output and diagnostic
output are set to /dev/null; all other file-descriptors are closed; the environment variables
$USER, $HOME, $SHELL are set appropriately, and no other environment variables exist.

The process is given a certain amount of time to execute. If the process does not exit
within this limit, the process will be terminated with extreme prejudice. The amount of time
is calculated as ((size / 60) + 300) seconds, where size is the number of bytes in the mes‐
sage (with 30 minutes the maximum time allowed).

The exit status of the process is consulted in determining the success of the action. An
exit status of zero means that the action succeeded. Any other exit status (or abnormal ter‐
mination) means that the action failed.

In order to avoid any time limitations, you might implement a process that began by
fork()-ing. The parent would return the appropriate value immediately, and the child could
continue on, doing whatever it wanted for as long as it wanted. This approach is somewhat
risky if the parent is going to return an exit status of zero. If the parent is going to re‐
turn a non-zero exit status, then this approach can lead to quicker delivery into your mail
drop.

FILES
/etc/nmh/mts.conf nmh mts configuration file
$HOME/.maildelivery The file controlling local delivery
/etc/nmh/maildelivery Rather than the standard file
/var/mail/$USER The default mail drop

SEE ALSO
rcvdist(1), rcvpack(1), rcvstore(1), rcvtty(1), mh-format(5)

DEFAULTS
`-noverbose'
`-nosuppressdup'
`-maildelivery' defaults to $HOME/.maildelivery
`-mailbox' defaults to /var/mail/$USER
`-file' defaults to stdin
`-addr' defaults to the current user
`-user' defaults to the current user

-addr and -user will be set the the user part of the Local-Mailbox profile entry, if set.

CONTEXT
None

HISTORY
slocal was originally designed to be backward-compatible with the maildelivery facility pro‐
vided by MMDF-II. Thus, the “.maildelivery” file syntax is somewhat limited. But slocal has
been modified and extended, so that is it no longer compatible with MMDF-II.

In addition to an exit status of zero, the MMDF values RP_MOK (32) and RP_OK (9) mean that
the message has been fully delivered. Any other non-zero exit status, including abnormal
termination, is interpreted as the MMDF value RP_MECH (200), which means “use an alternate
route” (deliver the message to the mail drop).

BUGS
Only two return codes are meaningful, others should be.

slocal was originally designed to be backwards-compatible with the maildelivery functionality
provided by MMDF-II.

nmh-1.7.1 2016-05-02 SLOCAL(1mh)