01-20-2006
Quote:
Originally Posted by rmulchandani
I have a script which must not be run more than once at any given time. THis script will be scheduled to run every 20 mins as a cron job.
In my script can i have logic to say if this script is already running from the previous cron, then exit.
How do i go about doing that. If you describe the approach, can you please specify just the commands, which i can man to construct my approach.
Because I am not familiar with unix commands, if you tell me "find the file and do stuff..." i may not know the command to "find the file".
thanks!
write a tmp file to the /tmp directory.
have your script check to see if the file exists, if it does then don't run.
#!/bin/sh
# our tmpfile
tmpfile="/tmp/mytmpfile"
# check to see if it exists.
# if it does then exit script
if [[ -f ${tmpfile} ]]; then
echo script already running.
exit
fi
# it doesn't exist at this point so lets make one
touch ${tmpfile}
# do whatever now.
# end of script
rm ${tmpfile}
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LEARN ABOUT SUNOS
tmpfile
tmpfile(3C) Standard C Library Functions tmpfile(3C)
NAME
tmpfile - create a temporary file
SYNOPSIS
#include <stdio.h>
FILE *tmpfile(void);
DESCRIPTION
The tmpfile() function creates a temporary file and opens a corresponding stream. The file will automatically be deleted when all refer-
ences to the file are closed. The file is opened as in fopen(3C) for update (w+).
The largest value that can be represented correctly in an object of type off_t will be established as the offset maximum in the open file
description.
RETURN VALUES
Upon successful completion, tmpfile() returns a pointer to the stream of the file that is created. Otherwise, it returns a null pointer and
sets errno to indicate the error.
ERRORS
The tmpfile() function will fail if:
EINTR A signal was caught during the execution of tmpfile().
EMFILE There are OPEN_MAX file descriptors currently open in the calling process.
ENFILE The maximum allowable number of files is currently open in the system.
ENOSPC The directory or file system which would contain the new file cannot be expanded.
The tmpfile() function may fail if:
EMFILE There are FOPEN_MAX streams currently open in the calling process.
ENOMEM Insufficient storage space is available.
USAGE
The stream refers to a file which is unlinked. If the process is killed in the period between file creation and unlinking, a permanent
file may be left behind.
The tmpfile() function has a transitional interface for 64-bit file offsets. See lf64(5).
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Interface Stability |Standard |
+-----------------------------+-----------------------------+
SEE ALSO
unlink(2), fopen(3C), mkstemp(3C), mktemp(3C), tmpnam(3C), lf64(5), standards(5)
SunOS 5.10 4 Aug 2003 tmpfile(3C)