The crontab in ubuntu was creating muntiple files with same name as the file in execution.
I was running the file fr_bom.php in cron tab and it created multiple file like this
fr_bom.php.409 fr_bom.php.410 fr_bom.php.411
I was wondering how do delete them suddenly it flashed to me that i should use wild card
I used rm fr_bom.php.* to remove all the files.
Also you can add a crontab to remove these files every day once like this each day at 6:30 PM.
30 18 * * * rm fr_bom.php.*