05-17-2014
How to check/compare lock file?
Hi all,
I have a shell script that I schedule to run from 0700 - 1900, every 15minutes. For each run it creates a lock file and remove it on exit.
While there is a bit of a flaw to it where the lock file don't get remove if someone kills the script while it is running, I am fairly satisfied with it. No one should be killing the script on purpose anyway unless the server itself rebooted and the script of course did not run its course where it is supposed to remove the lock file on exit.
Can someone advise how I can somehow check the timestamp of the lock file? For example, if the lock file is 30 or 45 minutes old, I assume the script may have been killed in which case instead of exiting because it exists, I want to remove it and continue the run of the script.
BTW, OS is Solaris 9.
Any advise much appreciated. Thanks in advance.
Last edited by newbie_01; 05-17-2014 at 07:59 AM..
Reason: Include OS information
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LEARN ABOUT LINUX
lockfile-progs
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. How-
ever, 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 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 incre-
ments) 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)
AUTHOR
Written by Rob Browning <rlb@defaultvalue.org>
0.1.12 2008-02-10 lockfile-progs(1)