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

mail-lock [ --retry retry-count ]

mail-unlock

mail-touchlock [ --oneshot ]

lockfile-create [ --retry retry-count ] filename

lockfile-remove filename

lockfile-touch [ --oneshot ] filename

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_create(3) call, but in fact, this option might be better named --tries since --retry 0 will not try to lock at all.

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

0

Successful program execution.

NOT-0

Some problem was encountered.

maillock(3), touchlock(3), mailunlock(3), lockfile-create(1), lockfile-remove(1), lockfile-touch(1), lockfile_create(3), lockfile_remove(3), lockfile_touch(3).

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