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shlock(1)


NAME

   shlock - create lock files for use in shell scripts

SYNOPSIS

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

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 if the process is currently running.
   If the process exists, then the file will not be created.

   Shlock exits with a zero status if it was able to create the lock file,
   or non-zero if the file refers to currently-active process.

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

   -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.

EXAMPLES

   The following example shows how shlock would be  used  within  a  shell
   script:
          LOCK=/run/innd/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> after a description of HDB
   UUCP locking given by Peter Honeyman.   This  is  revision  1.9,  dated
   1996/10/29.

                                                                 SHLOCK(1)



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