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

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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/, where 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
option applies to lockfile-create and lockfile-check. NOTE: this
option will not work correctly between machines sharing a filesys‐
tem.

-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
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 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

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