system crontab

[Zbigniew Szalbot]

Hello,

I would like to daily run a certain script that cleans exim's queue from 
frozen messages:

sudo exiqgrep -i -z | sudo xargs -L 1 exim -Mrm

I have created a file called rm_frozen_msg.sh, gave it appropriate 
permissions and then installed it in my user crontab. Because it did not 
work I read the man and found out that I cannot run scripts as another 
(root) user. Therefore I edited /etc/crontab to instruct it to run the 
file daily.

At first, it did not like sudo. As I was running it under user root 
anyway, I deleted sudo from the file. Then it complained about 
exiqgrep so I put the full path: /usr/local/sbin/

But my question is why can I run the command

sudo exiqgrep -i -z | sudo xargs -L 1 exim -Mrm

from the command line but I cannot use it in a file with cron?

Thanks!

--
Zbigniew Szalbot