.\" $Revision: 5794 $
.TH SHLOCK 1
.SH NAME
shlock \- create lock files for use in shell scripts
.SH SYNOPSIS
.B shlock
.BI \-p " pid"
.BI \-f " name"
[
.B \-b
]
[
.B \-u
]
[
.B \-c
]
.SH DESCRIPTION
.I Shlock
tries to create a lock file named
.I name
and write the process ID
.I pid
into it.
If the file already exists,
.I 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.
.PP
.I 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.
.SH OPTIONS
.TP
.B \-b
Process IDs are normally read and written in ASCII.
If the ``\-b'' flag is used, then they will be written as a binary
.IR 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.
.TP
.B \-c
If the ``\-c'' flag is used, then
.I 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
.I shlock
without the flag would have succeeded), then the program will exit
with a zero status.
.SH EXAMPLES
The following example shows how
.I shlock
would be used within a shell script:
.RS
.nf
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}`
f\&i
.fi
.RE
.SH BUGS
.I shlock
assumes that it will not be used in an environment with multiple
locks/unlocks in a short time (due to a race condition).  That is,
.I shlock
is intended for daily or hourly jobs.
.SH HISTORY
Written by Rich $alz <rsalz@uunet.uu.net> after a description of HDB UUCP
locking given by Peter Honeyman.
.de R$
This is revision \\$3, dated \\$4.
..
.R$ $Id: shlock.1 5794 2002-10-01 23:31:53Z vinocur $
.SH "SEE ALSO"
inn.conf(5)