'cron' and 'at'

lawrence_lee_lee · 01-09-2008, 09:43 PM

I know that both 'cron' and 'at' commands are related to executing some command at a particular time. But I don't know how to use them. I tried to man it but it was not detailed enough for me to learn.

Can anyone briefly explain how to use them? What's their difference? When to use which?

For example, if I want to generate a text file name 'touch_this.txt' in my home folder at 23:00 tonight. (ie. execute "touch ~/touch_this.txt"). How should I do this using either/both "at" or/and "cron"?

Thanks very much.

Uncle_Theodore · 01-09-2008, 09:52 PM

at executes the command(s) given to it once at a specified time on a specified date.
cron executes the command(s) given to it repeatedly at a specific time or date every day, week or every month. That's pretty much the difference between the two.

lawrence_lee_lee · 01-10-2008, 12:08 AM

I expect that the log file for "cron" to be found in/var/log/cron but I cannot find this file in my system. Is this related to my distro of Linux? I am using Ubuntu7.10. Where can I find the log file?

Uncle_Theodore · 01-10-2008, 12:25 AM

Have you checked /var/log/crond? There are several possible setups, yes, it might depend on a distro.

lawrence_lee_lee · 01-10-2008, 02:28 AM

I've checked, but found nothing related.

Quote:

ls /var/log/*cron*

give me nothing.

jlinkels · 01-10-2008, 05:21 AM

Check /var/log/syslog or /var/log/messages. Cron logging is marked with [CRON]

jlinkels

lawrence_lee_lee · 01-11-2008, 01:12 AM

Thanks! I've finally found it!