mail-lock

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 [--use-pid] [--retry retry-count]
       mail-unlock
       mail-touchlock [--oneshot]

       lockfile-create [--use-pid] [--retry retry-count] [--lock-name] filename
       lockfile-remove [--lock-name] filename
       lockfile-touch [--oneshot] [--lock-name] filename
       lockfile-check [--use-pid] [--lock-name] filename

DESCRIPTION
       Lockfile-progs provides a set a programs that can be used 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

           lockfile-create - lock a given file
           lockfile-remove - remove the lock on a given file
           lockfile-touch - touch the lock on a given file
           lockfile-check - check the lock on a given file

       By  default, the filename argument refers to the name of the file to be
       locked, and the name of the lockfile will be filename .lock.   However,
       if  the  --lock-name argument is specified, then filename will be taken
       as the name of the lockfile itself.

       Each   of   the   mail    locking    commands    attempts    to    lock
       /var/spool/mail/<user>,  where  <user>  is the name associated with the
       effective user ID, as determined by via geteuid(2).

       Once a file is locked, the lock must be touched  at  least  once  every
       five  minutes or the lock will be considered stale, and subsequent lock
       attempts will succeed.  Also see the --use-pid  option  and  the  lock-
       file_create(3) manpage.

       The  lockfile-check  command  tests whether or not a valid lock already
       exists.

OPTIONS
       -q, --quiet
           Suppress any output.  Success or failure will only be indicated  by
           the exit status.

       -v, --verbose
           Enable diagnostic output.

       -l, --lock-name
           Do  not append .lock to the filename.  This option applies to lock-
           file-create, lockfile-remove, lockfile-touch, or lockfile-check.

       -p, --use-pid
           Write the parent process id (PPID) to the lockfile whenever a lock-
           file  is created, and use that pid when checking a lock's validity.
           See the lockfile_create(3) manpage for more information.  This  op-
           tion applies to lockfile-create and lockfile-check.  NOTE: this op-
           tion will not work correctly between machines sharing a filesystem.

       -o, --oneshot
           Touch the lock and exit immediately.  This option applies to  lock-
           file-touch  and  mail-touchlock.  When not provided, these commands
           will run forever, touching the lock once every minute until killed.

       -r retry-count, --retry retry-count
           Try to lock filename retry-count times before giving up.  Each  at-
           tempt  will  be delayed a bit longer than the last (in 5 second in-
           crements) until reaching a maximum delay of one minute between  re-
           tries.   If retry-count is unspecified, the default is 9 which will
           give up after 180 seconds (3 minutes) if all 9 lock attempts fail.

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
           For lockfile-check this indicates that a valid lock exists,  other-
           wise it just indicates successful program execution.

       Not 0
           For lockfile-check a non-zero exit status indicates that the speci-
           fied lock does not exist or is not valid.  For  other  programs  it
           indicates that some problem was encountered.

SEE ALSO
       maillock(3)
       touchlock(3)
       mailunlock(3)
       lockfile_create(3)
       lockfile_remove(3)
       lockfile_touch(3)
       lockfile_check(3)

AUTHOR
       Written by Rob Browning <rlb@defaultvalue.org>

0.1.12                            2008-02-10                 lockfile-progs(1)