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GNU/Linux |
Debian 6.0.0(Squeeze) |
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lockfile-create(1) |
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lockfile−progs − command−line programs to safely lock and unlock files and mailboxes (via liblockfile).
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
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.
−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 current process id (PID) 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, lockfile−remove, lockfile-touch, and lockfile-check.
−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.
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
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.
maillock(3)
touchlock(3)
mailunlock(3)
lockfile_create(3)
lockfile_remove(3)
lockfile_touch(3)
lockfile_check(3)
Written by Rob Browning <rlb@defaultvalue.org>
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lockfile-create(1) | |