Running scheduled tasks

Running scheduled tasks

If you are doing a repetitive task on your system, it is better to automate. For example, you may want to sync fi les between two systems at a regular interval. Instead of doing it yourself manually, you can create a scheduled task that automatically runs at the configured intervals. In Linux (and most UNIX environments) this is achieved through cron. Cron is a time-based task scheduler. To create a scheduled tasks using cron…

01 Run the following command to open the

current user’s crontab fi le:

$ crontab -e

If you want a task to be run using root privileges,

you should use the command:

$ sudo crontab –e

02 The crontab fi le will then open in the default

text editor.

The default text editor can be set up using the

EDITOR environment variable:

$ export EDITOR=nano

Crontab takes input in the following format:

minute(0-59) hour(0-23) day(1-31)

month(1-12) weekday(0-6) command

An asterisk ( * ) is used as wild card. For example,

using asterisk with month will cause the task to

run every month.

03 Let’s assume that you want to run /usr/bin/

myludapp every day at 12.30 AM. So we will need

to create the following line in it:

29 0 * * * /usr/bin/myludapp

Here, 29 is for the 30-minute mark and 0 for

12 am because the minute, hour and weekday

values start at 0. However, the day and month

values start at 1 instead of 0.