special cronjob scheduling

Question

I have three scripts and want every one of them to run every 3 minutes, but in way that every minute a different script is running.

for example

00:00 script1 is executed
00:01 script2 is executed
00:02 script3 is executed
00:01 script1 is executed

Is there a way to make this work via crontab in Debian?

At the moment I have it like this:

*/3 * * * * php /Scripts/script1.php &> /dev/null
*/3 * * * * php /Scripts/script2.php &> /dev/null
*/3 * * * * php /Scripts/script3.php &> /dev/null

but this would run all the scripts all 3 minutes

Answer 1

Call a wrapper script every minute. This wrapper script looks at (minutes % 3) and calls the correct script using the remainder.
Only one line in cron: nice.

EDIT: New thoughts You can skip the wrapper by introducing an ugly crontab line.
I would go for the wrapper (cleaner crontab, place to set and export variables, additional control statements), but I think you should know about the possibilities.
Make the testfiles x0, x1 and x2 in /tmp, chmod +x them, with the content

echo $(date) $0 >> /tmp/x.out

Make a crontab line

* * * * * /tmp/x`echo "$(date '+\%M') \% 3" | bc`

Wait 5 minutes (maybe get coffee black for me?) and look at /tmp/x.out.
Remove the crontab entry and the new /tmp/x* files.

Answer 2

There might be fancier ways, but the dead simple way is just to list out the minutes you want them to run on (and the rest would of course be * for hours, days, etc):

0,3,6,9,12,15,18,21,24,27...
1,4,7,10,13,16,19,22,25,28...
2,5,8,11,14,17,20,23,26,29...