exim_lock

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 sec-
       ond argument is run as a command (using C's  "system()"  function);  if
       there  is  no second argument, the value of the SHELL environment vari-
       able is used; if this is unset or empty, /bin/sh is run.  When the com-
       mand  finishes, the mailbox is unlocked and the utility ends.  The fol-
       lowing 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 exclu-
              sive 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  mail-

         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)