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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TMPFILE(3) 1 TMPFILE(3)
tmpfile - Creates a temporary file
SYNOPSIS
resource tmpfile (void )
DESCRIPTION
Creates a temporary file with a unique name in read-write (w+) mode and returns a file handle .
The file is automatically removed when closed (for example, by calling fclose(3), or when there are no remaining references to the file
handle returned by tmpfile(3)), or when the script ends.
For details, consult your system documentation on the tmpfile(3) function, as well as the stdio.h header file.
RETURN VALUES
Returns a file handle, similar to the one returned by fopen(3), for the new file or FALSE on failure.
EXAMPLES
Example #1
tmpfile(3) example
<?php
$temp = tmpfile();
fwrite($temp, "writing to tempfile");
fseek($temp, 0);
echo fread($temp, 1024);
fclose($temp); // this removes the file
?>
The above example will output:
writing to tempfile
SEE ALSO
tempnam(3), sys_get_temp_dir(3).
PHP Documentation Group TMPFILE(3)