Per-user cronjob (somewhat automatically)

Question

Hi all,
probably some of you have a solution for this already in place:
I have switched from fetchmail to mpop and miss the daemon feature. When I tried to launch mpop with the following mpop file in /etc/cron.d, it didn't work (I think it didn't download any messages, probably due to the fact that my mpoprc/mailbox definition is in my personal home dir. But even with su it didn't work.):
*/10 * * * * su wagner -c /usr/bin/mpop -qa
With the crontab command, however I can insert it in my personal crontab and it's working fine. Now should I put such a crontab command in my .profile or what?
Second, I would like to automatically enable/disable that cronjob dependng on whether I'm on-line or not, and
thirdly, I would like to be able to call mpop manually (I have a keybinding in mutt for that), but that should be a nop when the cronjob is just executing.
Thanks for any hints,
Andreas

Answer 1

First, the cron daemon executes job from the crontabs of any user: so just edit the crontab of the user with 'crontab -e -u <user>' and the cron daemon will do everything.
For the verification of the internet connection, you can use a script which pings some hosts and executes the action only if the ping is successful:
#!/bin/bash
IP1=0.0.0.0 # enter an IP address here
IP2=0.0.0.0 # enter an IP address here
IP3=0.0.0.0 # enter an IP address here
IP4=0.0.0.0. # enter an IP address here
COMMAND=$1
STATUS=Up
ping -c1 $IP1
if [ $? != 0 ]; then
ping -c1 $IP2
if [ $? != 0 ]; then
ping -c1 $IP3
if [ $? != 0 ]; then
ping -c1 $IP4
if [ $? != 0 ]; then
STATUS=Down
echo "down"
fi
fi
fi
fi
if [ $STATUS = Up ]; then
echo "up"
exec $COMMAND
fi
Call this script e.g. 'netex', and then use 'netex <yourdesiredaction>' as a cron job definition.
On the first point I do not know, but many mail fetchers use a lock to prevent a double execution (e.g. fdm). I do not know mpop so I do not know how to get the same result.