If you need a certain Linux script, command, or program to regularly run at a certain time, you can schedule the event (called a "job") using cron. We'll show you how to open your cron configuration file and schedule your first cron job.
Setting up the File
Using your favourite editor, create a cron file with a line for each job you wish to schedule, in the format:
m h d m w command
- m minute
- h hour
- d day of month
- m month 1-12
- w weekday 0-7, Sun,Mon, etc (Sunday = 0 = 7) It is easy to remember if you think of the way one would say a date: Wednesday, July 29, at 10:30, then reverse the order.
Load your file into crontab:
crontab yourfile
Trying an Example
Create a file testCron.txt containing the following lines:
- # do this every 10 minutes
- */10 * * * * date >> ~/testCron.log
Load it into cron:
crontab testCron.txt
Wait 30 minutes, check testCron.log, if it works it will update your file with a time stamp 3 times.
Remove the crontab so that it does not run forever:
crontab -r
Tips
- You may directly edit your crontab using crontab -e; note it uses vi syntax which can be awkward for the new user.
- ALWAYS with *nix use the man pages, they are your friends: man crontab