I need to modify crontab through a script, but I've read that if I modify the file directly, cron won't pick up the changes.

Has anyone managed to write a cron file directly and for the changes to work? If so any tips?

Thanks

1) run "crontab -l > tempcrontab"
2) edit your tempcrontab
3) run "crontab tempcrontab"

Or, just do Edit: Didn't notice the "script" part.

why are you trying to modify crontab through a script?
don't do it, bad medicine.
why not use 'at' or 'batch' ?

Thanks for the replies so far, I'm making progress. The system I'm working on is for an intranet only, so I'm not too worried about security for now. I want the user to change some stuff on cron through a web interface, so that the box will run the jobs on booting only, i.e. no user logged in.

If I'm correct, then cron needs to be modified by root. If that's not correct, then let me know, as I'm running into some problems. My script to modify cron works when I call it from root, but when I call it from the web interface it tries to modify cron for 'nobody'. So that won't run on boot? I tried to modify for root, by 'su', but I get the error:

su: must be run from a terminal

So now I'm stuck. If cron for nobody runs at boot, then no problem. Can anyone please enlighten me.

Thanks

Well they say a little knowledge is dangerous. crontab as nobody will run on boot. So all my script stuff is as nobody and it's working great.