following is what i have read in the book Ubuntu complete reference by Richard Petersen, page no: 463
Running cron Directory Scripts
Each directory contains scripts that are all run at the same time. The scheduling for each group is determined by an entry in the /etc/crontab file. The actual execution of the scripts is performed by the /usr/bin/run-parts script, which runs all the scripts and programs in a given directory. Scheduling for all the tasks in a given directory is handled by an entry in the /etc/crontab file. Linux provides entries with designated times, which you may change for your own needs.
but i didn't find the script /usr/bin/run-parts script in my machine ?
so what could be the script that does the actual execution of crontab entries ?