UNIX for Dummies Questions & Answers

Hi guys,

How can I specify the start and end time of a cron job. And my start time and end time are specified by minutes. For example, I want to set up a cron runs every 3 minutes from 18:40 to midnight. How can i do this please? Many thanks

Best regards,
Clu

If I were doing this, I'd kick off a script at 18:40, just once, and let it run your programme/script every three minutes until midnight.

Code:

#!/usr/bin/env ksh

while true
do
    d=$( date +%H )
    if (( $d == 0 ))
    then
        exit
    fi

    echo "run your command here"
    sleep 180
done

Your crontab entry would be simple:

Code:

40 18 * * * /path/to/your/script.ksh >/tmp/script.log 2>&1

If the command you are running takes several minutes to run, and you want it to start right at the next three minute mark, run it asynchronously (use &) so that the waking from the sleep is 3 minutes from when the programme started and not three minutes from when the programme ended.

Hi agama,

Many thanks for this. We can't change the script that we are going to schedule in the cron. Does it mean this can't be done in one line of cron? Thanks.

Can

You wouldn't need to change the script, add a new one that invokes the one you were going to start from cron. If you cannot add a new script, then you'll end up with two entries in the crontab.

Code:

40-59/3 18 * * * /path/to/script >>/tmp/script.log 2>&1
*/3 19-23 * * * /path/to/script >>/tmp/script.log 2>&1

Note that some versions of cron do not support */3 notation.

Hi agama,

Ideally I'd like to create a new script to invoke the required script as recommended, in case I can't I'll go with your second suggestion.

Many thanks for your help.

Best regards,
clu