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Full Discussion: How to check/compare lock file?
Top Forums Shell Programming and Scripting How to check/compare lock file? Post 302902056 by cnamejj on Sunday 18th of May 2014 12:20:53 AM
Old 05-18-2014
Here's a quick demonstration how "flock" can be used to coordinate serialized execution of a command. When you enter the following,

Code:
iter=0
while [ ${iter} -lt 10 ]
do
    flock -w 30 /var/tmp/test-flock.lock -c 'sleep 4; date' &
    iter="$(( ${iter} + 1 ))"
done

will start up 10 "flock" commands in parallel. But they will only run their respective payloads "sleep 4; date" when they can get an exclusive lock on the file "/var/tmp/test-flock.lock".

As a result, they will be serialized and run one at a time. You can tell that's the case because the time echo'd to your terminal will be 4 seconds apart.

Also, since each "flock" will only wait 30 second to get the exclusive lock, two of them will timeout and NOT run the "sleep 4; date" commands. And since it's using actual filesystem lock calls, you don't need to create or remove the lockfile. If it doesn't exist, it will be created for you. And there's no need to remove either.
 

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LEARN ABOUT OSF1

lock

lock(9s)																  lock(9s)

NAME

       lock - General: Contains complex lock-specific information

SYNOPSIS

       The lock data structure is an opaque data structure; that is, its associated members are referenced and manipulated by the operating system
       and not by the user of the complex lock mechanism. Therefore, this reference page omits a description of the lock data structure's  associ-
       ated members.

DESCRIPTION

       The  lock  data	structure  is the complex lock structure that contains complex lock-specific information. A kernel module writer using the
       complex lock method declares a pointer to a lock data structure and passes its address to the associated lock routines.

NOTES

       The header file <lock.h> shows typedef statements that assign the alternate name lock_data_t for the complex lock structure and lock_t  for
       a pointer to the complex lock structure.

FILES

SEE ALSO

       Routines: lock_done(9r), lock_init(9r), lock_read(9r), lock_terminate(9r), lock_try_read(9r), lock_try_write(9r), lock_write(9r)

       Data Structures: slock(9s)

																	  lock(9s)
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