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 lockfile_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  lockfile-create,
           lockfile-remove, lockfile-touch, or lockfile-check.

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

       -o, --oneshot
           Touch the lock and exit  immediately.   This  option  applies  to  lockfile-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 attempt will be delayed
           a  bit longer than the last (in 5 second increments) until reaching a maximum delay of
           one minute between retries.  If retry-count is unspecified, the  default  is  9  which
           will give up after 225 seconds 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,  otherwise it just
           indicates successful program execution.

       Not 0
           For lockfile-check a non-zero exit status indicates that the specified 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>