9
2012
Linux Cron Configuration
An article by Bülent Özkan
Cron is a scheduled task mechanism for unix/linux environment.
Cron main configuration file is /etc/crontab. Additionally cron has folders which will run hourly (/etc/cron.hourly), daily (/etc/cron.daily) and monthly (/etc/cron.monthly).
Cron commands :
crontab -e >> edits crontab file with vi editor.
crontab -l >> lists cron entries.
Creating scheduled jobs :
To create a scheduled script you should edit /etc/crontab file :
Crontab file structure :
* means every.
*/5 9 31 * * /home/user/test.pl
# .—————- Second (0 – 59)
# | .————- Hour (0 – 23)
# | | .———- Date of Month (1 – 31)
# | | | .——- Month (1 – 12) or jan,feb,mar,apr …
# | | | | .—– Date of Week (0 – 6) (Sunday=0 or 7) veya sun,mon,tue,wed,thu,fri,sat
# | | | | |
# * * * * *
Examples :
Script will run every 30 seconds :
*/30 * * * * /scriptPath
Everyday 14:00 and 21:00
00 14,21 * * * /scriptPath
Everyday and every-hour between 09:00 and 18:00
00 09-18 * * * /scriptPath
Every weekday(Monday to Friday) between 09:00 and 18:00
00 09-18 * * 1-5 /scriptPath
