Linux Fundamentals - Part 10: Bash Scripting (Crontab)

Source: Dev.to

Crontab

Crontab (cron table) is a text file used to schedule commands or scripts to run automatically at specified times on Unix‑like systems. These scheduled tasks are called cron jobs. The cron daemon checks the tables of scheduled tasks and executes them accordingly. Each user can have their own crontab file, making cron jobs flexible for both system‑wide and user‑specific automation.

Editing a crontab

crontab -e

This opens your crontab file in the default editor. Each line in the file represents a scheduled task using the following format:

* * * * * /full/path/to/command
| | | | |
| | | | └─ Day of Week (0–7) (Sunday = 0 or 7)
| | | └─── Month (1–12)
| | └───── Day of Month (1–31)
| └─────── Hour (0–23)
└───────── Minute (0–59)

Example Schedules

Run a script every day at 6 AM

0 6 * * * /home/user/backup.sh

Run every 10 minutes

*/10 * * * * /usr/bin/python3 /home/user/script.py

Run every Monday at midnight

0 0 * * 1 /home/user/monday_job.sh

Run at 3:30 PM on the first day of the month

30 15 1 * * /home/user/monthly_report.sh

Special Keywords

Cron provides shortcuts for common schedules:

Example

@daily /home/user/daily_cleanup.sh

Managing Your Crontab

• List all cron jobs for the current user:

  crontab -l

• Edit the crontab again (e.g., with Vim):

  crontab -e

Making Scripts Executable

chmod +x /home/user/script.sh

Today, I learned how to use crontab to schedule tasks in Linux. I discovered how cron jobs work, how to define time schedules using cron syntax, and how to manage scheduled tasks using Vim as my editor.