shlock(1)



SHLOCK(1)                 InterNetNews Documentation                 SHLOCK(1)

NAME
       shlock - Create lock files for use in shell scripts

SYNOPSIS
       shlock [-b|-c|-u] -f name -p pid

DESCRIPTION
       shlock tries to create a lock file named name and write the process ID
       pid into it.  If the file already exists, shlock will read the process
       ID from the file and test to see whether the process is currently
       running.  If the process exists, then the file will not be created.
       shlock exits with a zero status if it could create the lock file, or
       non-zero if the file refers to a currently active process.

       A Perl wrapper around shlock can be used via the "INN::Utils::Shlock"
       module.

OPTIONS
       -b  Process IDs are normally read and written in ASCII.  If the -b flag
           is used, then they will be written as a binary int.

       -c  If the -c flag is used, then shlock will not create a lock file,
           but will instead use the file to see if the lock is held by another
           program.  If the lock is valid, the program will exit with a non-
           zero status; if the lock is not valid (i.e. invoking shlock without
           the flag would have succeeded), then the program will exit with a
           zero status.

       -f name
           name is the name of the lock file shlock attempts to create.  If
           the file already exists, it will read the process ID from the file
           and exit with a non-zero status if this process is currently
           active.

       -p pid
           pid is the process ID to write into the file name.

       -u  For compatibility with other systems, the -u flag is accepted as a
           synonym for -b since binary locks are used by many UUCP packages.

EXAMPLES
       The following example shows how shlock would be used within a shell
       script:

           LOCK=<pathrun in inn.conf>/LOCK.send
           trap 'rm -f ${LOCK} ; exit 1' 1 2 3 15
           if shlock -p $$ -f ${LOCK} ; then
               # Do appropriate work.
           else
               echo "Locked by `cat ${LOCK}`"
           fi

HISTORY
       Written by Rich $alz <rsalz@uunet.uu.net> for InterNetNews after a
       description of HDB UUCP locking given by Peter Honeyman, and improved
       by Berend Reitsma to solve a race condition.  Converted to POD by
       Julien Elie.

       $Id: shlock.pod 9303 2011-08-04 22:09:57Z iulius $

SEE ALSO
       INN::Utils::Shlock(3pm).

INN 2.6.2                         2015-09-12                         SHLOCK(1)

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