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=/news/locks/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  descrip-
     tion  of  HDB UUCP locking given by Peter Honeyman.  This is
     revision 1.9, dated 1996/10/29.