So you need to run some script that you’ve created at certain times on certain days and you don’t know anything about cron. You’ve come to the right place. I am about to show you the basics of the Unix/Linux crontab:
Below are some basic crontab commands:
export EDITOR=vi – This sets up a default editor for the crontab to use.
crontab -e Edit your crontab file, or create one if it doesn’t already exist.
crontab -l Display your crontab file.
crontab -r Remove your crontab file.
crontab -v Display the last time you edited your crontab file.
A crontab file has five fields for specifying day , date and time followed by the command to be run at that interval.
* * * * * command to be executed
- - - - -
| | | | |
| | | | +—– day of week (0 – 6) (Sunday=0)
| | | +——- month (1 – 12)
| | +——— day of month (1 – 31)
| +———– hour (0 – 23)
+————- min (0 – 59)
Sample crontab entry to run a the unix remove command to remove some temporary files:
30 * * * * rm /tmp/*.tmp
This runs a rm comand and removes all files that end in .tmp from the /tmp directory every 30 minutes.