scripting crontab entries

[Lowell Gilbert]

Peter Risdon <peter at circlesquared.com> writes:

> I want to be able to update a user's crontab from a script. tabs
> in /var/cron/tabs carry a warning that the file should not be edited
> directly, so presumably something like
> 
> #echo "5 * * * *   /some/script.sh" >> /var/cron/tabs/$USER
> 
> is the wrong approach. Is the right approach:
> 
> #cat ~/.mycrontab
> 5 * * * *   /some/script.sh
> 
> #crontab ~/.mycrontab
> 
> The right way to go? I notice this approach blows away existing crontab
> entries, and was hoping to be able to append new ones instead, but then
> by treating ~/.mycrontab as the master file, I can manage this OK.

How about:

crontab -u $USER -l > crontab.file.$USER
echo "5 * * * *   /some/script.sh" >> crontab.file.$USER
crontab -u $USER crontab.file.$USER