mail-unlock (1)
Leading comments
** The above line should force tbl to be a preprocessor ** Man page for man Copyright (C), 1998-2008, Rob Browning <rlb@defaultvalue.org> You may distribute under the terms of the GNU General Public License as specified in the file COPYING that comes with the lockfile\-progs distribution.
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 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, 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)