Crontab Examples

Using crontab some times can get little confusing due to the field names, values, syntax, redirection. Learn crontab with different examples for each fields, you can use with minor modifications or create new ones based off these examples

Crontab Examples :

The fields used by crontab and their meaning.

crontab

Crontab Examples :

All the examples uses date command to show the command execution time but it can be substituted by any other command or program or script.

1. Every 15 minute – every hour,  every day 

15,30,45,00 * * * *   date >> /tmp/every15minutes

2.  Once in a hour at 10th minute, every hour,  every day

10 * * * *   date >> /tmp/everyHRat10minutes

3.  at 25th minute,   after 4 hrs , at 10 AM, 2pm 6pm, 10 pm ,  every day

25  10,14,18,22  * * *   date >> /tmp/everyHRat10inutes

4. Once in a day at 11.30 PM

30 23 * * *  date >> /tmp/everyHRat10inutes

 at 30 minutes past mid night 

30 00 * * * date >> /tmp/everyHRat10inutes

5. At 5 day intervals  at 10.10  AM every month 

10 10 5,10,15,20,25,30 * * 

Every 2nd  day of every month  at 10.20  AM every month 

10 10 2 * *   date >> /tmp/everyHRat10inutes

6. on 5th day  every quarter, 3 month interval ,  at 11.30  AM 

30 11 5 3,6,9,12 * date >> /tmp/everyHRat10inutes

on 5th day  on Jan and Feb only,   at 11.30  AM 

30 11 5 1,2 * date >> /tmp/everyHRat10inutes

once in a year on Jan 2nd at 11.30  AM 

30 11 2 1  * date >> /tmp/everyHRat10inutes

7.  Every Monday at 10.15 AM 

15 10 * * 1 

every Monday & Friday at 10.15 AM 

15 10 * * 1,5   date >> /tmp/everyHRat10inutes

Every weekday, except Saturday & Sunday

15 10 * * 1,2,3,4,5   date >> /tmp/everyHRat10inutes

8. disable email  by  redirecting output to  /dev/null  

10 * * * *   date >> /tmp/everyHRat10minutes >/dev/null  2>&1  

9. capture std out and std errors in a output file

10 * * * *   date >> /tmp/everyHRat10minutes > /tmp/outfile.log   2>&1  

10 Source env for the programs 

14 * * * *   source /home/app/.bashrc; .date

 

Further Reading :

Crontab – Quick Reference

What does 2>&1 mean in shell ?

 

 

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