Can I use variables in crontab file?

Question

I mean I want to use this variable at "minute to wday" in the following.

minute   hour    mday    month   wday    who command

Because I want to set these values in some configuration file and want to use those time spans here.

Answer 1

I don't think so that you can use variables as placeholder's there. Following is allowed

1. Numbers, ranges as hyphen- separated number which can again be separated using comma , example:

   for day-of-month you can write 2-4,8-10, if you need to run the job from 2^nd to 4^th and 8^th to 10^th day of month.

2. One of the following pre-defined ones

@reboot     :    Run once after reboot.
@yearly     :    Run once a year, ie.  "0 0 1 1 *".
@annually   :    Run once a year, ie.  "0 0 1 1 *".
@monthly    :    Run once a month, ie. "0 0 1 * *".
@weekly     :    Run once a week, ie.  "0 0 * * 0".
@daily      :    Run once a day, ie.   "0 0 * * *".
@hourly     :    Run once an hour, ie. "0 * * * *".

If you need something dynamic for a large list of job to be created, I suggest create a shell script that will dump the required crontab timings, which you can place in the crontab file.

unix man page for crontab

Answer 2

I think you have to use standard syntax for crontab and check for user/weekday inside your script.