slocal(1)

slocal -- special local mail delivery

Synopsis

/etc/mail/slocal [address info sender] [-addr address] [-info data] [-sender sender] [-user username] [-mailbox mbox] [-file file] [-home homedir] [-maildelivery deliveryfile] [-verbose] [-noverbose] [-debug] [-help]

Description

The slocal program allows 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 the Message Transfer Agent (MTA) on your system.

The message selection criteria used by slocal is specified in the file .maildelivery in the user's home directory. The format of this file is given on the maildelivery(4) manual page.

The message delivery address and message sender are determined from the MTA envelope information, if possible. Under sendmail(1M), the sender is obtained from the UUCP ``From'' line, if present. The user can override these values with command-line arguments or arguments to the -addr and -sender switches.

The message is normally read from the standard input. The -file option sets the name of the file from which the message should be read, instead of reading stdin. The -user option tells slocal the name of the user for whom it is delivering mail. The -mailbox option tells slocal the name of the user's maildrop file.

The -info option can be used to pass an arbitrary argument to subprocesses that slocal invoke on your behalf. The -verbose option causes slocal to give information to stdout about its progress. The -debug option produces more verbose debugging output on stderr.

slocal is the default local mail delivery agent. Normally, only the maildelivery file needs to be altered to enable slocal processing. If, for some reason, this has changed and you want to use slocal, include the following line in your .forward file in your home directory:

/etc/mail/slocal -user username

Subprocess environment

When a process is invoked, its environment is as follows:

The user and 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 variables $USER, $HOME, and $SHELL are set appropriately, and no other variables exist.

The process is given a certain amount of time to execute. If the process does not exit within this limit, it is terminated with extreme prejudice. The amount of time is calculated as ((size x 60) + 300) seconds, where size is the number of bytes in the message.

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

To avoid any time limitations, you can implement a process that begins by forking. The parent returns the appropriate value immediately, and the child continues doing whatever it wants for as long as it wants. This approach is somewhat risky if the parent returns an exit status of zero. If the parent returns a non-zero exit status, this approach can lead to quicker delivery into your maildrop.

Files

$HOME/.maildelivery: The file controlling local delivery.
/etc/mail/maildelivery: Rather than the standard file.
mailbox /var/mail/$USER: The default maildrop.

References

maildelivery(4)