SHLOCK(1)SHLOCK(1)NAMEshlock - create lock files for use in shell scripts
SYNOPSISshlock-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 cur
rently-active process.
OPTIONS-b Process IDs are normally read and written in ASCII.
If the ``-b'' flag is used, then they will be writ
ten 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 suc
ceeded), then the program will exit with a zero
status.
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> after a descrip
tion of HDB UUCP locking given by Peter Honeyman. This is
revision 1.5, dated 1998/04/09.
SEE ALSOinn.conf(5)SHLOCK(1)
