lockfile-progs

lockfile-progs(1)              Lockfile programs             lockfile-progs(1)



NAME
       lockfile-progs  - command-line programs to safely lock and unlock files
       and mailboxes (via liblockfile).

SYNOPSIS
       mail-lock [ --retry retry-count ]
       mail-unlock
       mail-touchlock [ --oneshot ]

       lockfile-create [ --retry retry-count ] filename
       lockfile-remove filename
       lockfile-touch [ --oneshot ] filename

DESCRIPTION
       lockfile-progs provide a method to lock and unlock mailboxes and  files
       safely (via liblockfile).

       mail-lock: lock the current user's mailbox.
       mail-unlock: unlock the current user's mailbox.
       mail-touchlock: touch the lock on the current user's mailbox.

       Each   of   the   mail   locking   commands  is  applied  to  the  file
       /var/spool/mail/<user>, if possible, where <user> is the  name  of  the
       current user (determined from the effective uid via geteuid(2)).

       lockfile-create: lock a given file.
       lockfile-remove: remove the lock on a given file.
       lockfile-touch: touch the lock on a given file.

       Once  a  file  is  locked, the lock must be touched at least once every
       five minutes, or it will be considered stale and a  subsequent  attempt
       to  lock  the  file  will  succeed.   For  both of the locking commands
       (mail-touchlock and lockfile-touch), the --oneshot argument causes  the
       program  to touch the lock and exit immediately.  Otherwise the program
       will loop forever, touching the lock once  every  minute  until  it  is
       killed.

       For  both  of the locking commands (mail-lock and lockfile-create), the
       --retry argument specifies (as an integer) the maximum number of  times
       to  retry  locking  the  file before giving up if attempts are failing.
       Each retry will be delayed a little longer than the last (in  5  second
       increments)  until  a  maximum  delay  of one minute between retries is
       reached.  The default retry count is 9 which, if all 9 attempts to lock
       the  file  fail, will give up after 180 seconds (3 minutes).  Note that
       the description above matches the one for the underlying  lockfile_cre-
       ate(3)  call,  but  in  fact, this option might be better named --tries
       since --retry 0 will not try to lock at all.


EXAMPLES
       Locking a file during a lengthy process:

         lockfile-create /some/file
         lockfile-touch /some/file &
         # Save the PID of the lockfile-touch process
         BADGER="$!"
         do-something-important-with /some/file
         kill "${BADGER}"
         lockfile-remove /some/file


EXIT STATUS
       0      Successful program execution.

       NOT-0  Some problem was encountered.

SEE ALSO
       maillock(3),  touchlock(3),  mailunlock(3),  lockfile-create(1),  lock-
       file-remove(1),     lockfile-touch(1),     lockfile_create(3),    lock-
       file_remove(3), lockfile_touch(3).

HISTORY
       1998 - Written by Rob Browning <rlb AT defaultvalue.org>.



0.1.10                           23 April 2001               lockfile-progs(1)