Schedule tasks on Linux

Is possible execute schedule task on Linux, for this we use the command cron or at. This post I will show how task schedule in your Linux.

Working the Cron

 No doub the cron is very utilized for Linux administrator. Your interface is very simples, we will look your functions! Just open the terminal and type command:

crontab -e

Sometimes the terminal will ask to use a text editor, select your favorite editor.

See contrab configuration:
# Edit this file to introduce tasks to be run by cron.
#
# Each task to run has to be defined through a single line
# indicating with different fields when the task will be run
# and what command to run for the task
#
# To define the time you can provide concrete values for
# minute (m), hour (h), day of month (dom), month (mon),
# and day of week (dow) or use '*' in these fields (for 'any').#
# Notice that tasks will be started based on the cron's system
# daemon's notion of time and timezones.
#
# Output of the crontab jobs (including errors) is sent through
# email to the user the crontab file belongs to (unless redirected).
#
# For example, you can run a backup of all your user accounts
# at 5 a.m every week with:
# 0 5 * * 1 tar -zcf /var/backups/home.tgz /home/
#
# For more information see the manual pages of crontab(5) and cron(8)
#
# m h  dom mon dow   command
Look the last lines having: m h dom mon dow comand

Means

m------------------> Minutes 00 59
h ------------------> Hours 00 23
dom--------------> Month day 1 31

mon -------------> Month 1 12
dow-------------->Week day 0 7
command ----> Command to execute task

Use * to specify every minutes, days, month and etc.

Examples, we go configure task the a script for incremental backup every day at 9PM.

# For more information see the manual pages of crontab(5) and cron(8)
#
# m h  dom mon dow   command
  00  21 *       *      *       /home/youruser/incremental\ backup.sh

Now every day at 9PM the cron run the script incremental backup.

Working the At

The command at is usefull to perform a task only once, example shutdown your computer.
The command At.

at HH:mm MM/DD/YYYY

Example on terminal

use@yourpc:$ at 20:00
at> shutdown -r now

press ctrl+d for save the task

For look the task scheduled type:

atq

For remove the task scheduled type:

atrm