How to Create a Cron Job and Execute at a Given Time in Linux

In this article, we will teach you on – how to schedule a corn job to execute at a specific time.

General Syntax of a Cron Job

MIN    HOUR    Day of month    Month    Day of Week    Command
0-59   0-23       1-31          1-12       0-6       linux command or script

To see a list of Cron Jobs which exists on the machine, run the below command –

# crontab -l
no crontab for root

To add the new cron job, run the below command –

#crontab -e
no crontab for root - using an empty one
Select an editor. To change later, run 'select-editor'.
1. /bin/ed
2. /bin/nano <---- easiest
3. /usr/bin/vim.basic
4. /usr/bin/vim.tiny
Choose 1-4 [2]:2
# 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

Scheduling a Job For a Specific Time

The basic usage of Cron is to execute a job in a specific time as shown below. This will execute the full backup shell script (full-backup) on 20th April 06:40 PM.

40 18 20 04 * /home/backups/full-backup


40 – 40th Minute
18 – 06 PM
20 – 20th Day
04 – 4th Month (April)
* – Every day of the week

At the end of the configuration you will be able to run a script or command at a specific time every day, like this we can specify the time for multiple executions with comma separeted values.

Sharon Christine
Sharon Christine

An investment in knowledge pays the best interest

Updated on: 21-Jan-2020

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