Understanding crontab

If we need to run a specific task repetitively, then the solution is to use crontab. The syntax of the command is as follows:

$ crontab -e

This will open a new editor. The following diagram is the syntax to add tasks. The fields to use for repeating tasks at a particular time are explained here:

Finally, to save the jobs, use the following:

Press Esc then type :wq

The preceding operations will save the job and quit crontab.

The following are a few examples of the crontab command:

• Use the following command to run a script every hour at the fifth minute, every day:

5 * * * *      $HOME/bin/daily.job >> $HOME/tmp/out  2>&1

• Use the following command to run 5 minutes after midnight every day:

5 0 * * *      $HOME/bin/daily.job >> $HOME/tmp/out  2>&1

• Use the following command to run at 2.15 p.m. on the first of every month–the output is mailed to Paul:

15 14 1 * * *     $HOME/bin/monthly

• Use the following command to run at 10 P.M. on weekdays, and send the email...