EXIM_LOCK(8)						      System Manager's Manual						      EXIM_LOCK(8)

NAME

       exim_lock - Mailbox maintenance

SYNOPSIS

       exim_lock [options]mailbox-file

DESCRIPTION

       The  exim_lock  utility	locks  a  mailbox  file  using	the same algorithm as Exim.  For a discussion of locking issues, see section 25.2.
       exim_lock can be used to prevent any modification of a mailbox by Exim or a user agent while investigating a problem.  The utility requires
       the  name  of  the file as its first argument.  If the locking is successful, the second argument is run as a command (using C's "system()"
       function); if there is no second argument, the value of the SHELL environment variable is used; if this is unset or empty, /bin/sh is  run.
       When the command finishes, the mailbox is unlocked and the utility ends.  The following options are available:

       -fcntl Use "fcntl()" locking on the open mailbox.

       -interval
	      This must be followed by a number, which is a number of seconds; it sets the interval to sleep between retries (default 3).

       -lockfile
	      Create a lock file before opening the mailbox.

       -mbx   Lock the mailbox using MBX rules.

       -q     Suppress verification output.

       -retries
	      This must be followed by a number; it sets the number of times to try to get the lock (default 10).

       -timeout
	      This must be followed by a number, which is a number of seconds; it sets a timeout to be used with a blocking "fcntl()" lock.  If it
	      is not set (the default), a non-blocking call is used.

       -v     Generate verbose output.

	      If none of -fcntl, -lockfile or -mbx are given, the default is to create a lock file and also use "fcntl()" locking on the  mailbox,
	      which  is  the same as Exim's default.  The use of -fcntl requires that the file be writable; the use of -lockfile requires that the
	      directory containing the file be writable.  Locking by lock file does not last for ever; Exim assumes that a lock file is expired if
	      it is more than 30 minutes old.

	      The  -mbx  option  is mutually exclusive with -fcntl.  It causes a shared lock to be taken out on the open mailbox, and an exclusive
	      lock on the file /tmp/.n.m where n and m are the device number and inode number of the mailbox file.  When the locking is  released,
	      if an exclusive lock can be obtained for the mailbox, the file in /tmp is deleted.

	      The  default  output  contains verification of the locking that takes place.  The -v option causes some additional information to be
	      given.  The -q option suppresses all output except error messages.

       A command such as

	 exim_lock /var/spool/mail/spqr

       runs an interactive shell while the file is locked, whereas

	 exim_lock -q /var/spool/mail/spqr <<End
	 <some commands>
	 End

       runs a specific non-interactive sequence of commands while the file is locked, suppressing all verification output.  A single  command  can
       be run by a command such as

	 exim_lock -q /var/spool/mail/spqr     "cp /var/spool/mail/spqr /some/where"

       Note that if a command is supplied, it must be entirely contained within the second argument - hence the quotes.

BUGS

       This manual page needs a major re-work. If somebody knows better groff than us and has more experience in writing manual pages, any patches
       would be greatly appreciated.

SEE ALSO

       exim(8), /usr/share/doc/exim4-base/

AUTHOR

       This manual page was stitched together from spec.txt by Andreas Metzler <ametzler at downhill.at.eu.org>, for the Debian  GNU/Linux  system
       (but may be used by others).

								  March 26, 2003						      EXIM_LOCK(8)