Cron/Crontab Question
 

In the past I have put entries in my crontab in the following form:
0 6 * * 6 cd /root/scripts; ./backup_net.sh; > /dev/null 2> /dev/null

Can someone explain to me exactly what the > /dev/null and 2> /dev/null do?

What I would like to happen is to get emailed with a simple success or failure. If the > /dev/null and 2> /dev/null are left off I get sent the output of the commands which could be lengthy.

Any thoughts?

With the command you've posted the shell will redirect error output (2) to std output and pipe std output (1 or nothing) to null.
You could squish that as "2>&1>/dev/null" .
If you only want the error output, just pipe stdout to null:
</path/to/>backup_net.sh > /dev/null

If you OTOH want better control over error output best thing is to rework your backup script to use error values.
An example could be:
cmd=bin/false; ${cmd} 2>/dev/null; case "$?" in
0) printf "%s${cmd} went OK\n";;
1) printf "%sError running ${cmd}\n";;
*) printf "%sError running ${cmd} (err: $?)\n";;
esac
...which will return 127 for "command not found", if you fix the path, it will return "1", as false always will.

unSpawn is right - what I also do though is output to a file - eg
0 6 * * 6 cd /root/scripts; ./backup_net.sh; 2>&1>/tmp/mycron.log

Then create a scipt that e-mails me mycron.log (or a parsed version that only sends lines with errors on it)