I'm doing a research project that requires I monitor cron jobs on a Ubuntu Linux system. I have collected data about the jobs' tasks and when they are started, I just don't know of a way to monitor how long they take to finish running.
I could calculate the time of finishing the task minus starting it with something like this but that would require doing that on the Shell scripts of each cron job. That's not necessarily difficult by any means but it seems a little silly that cron wouldn't in some way log this, so I'm trying to find an easier way :P
tl;dr Figure out time cron jobs take from start to finish
You could just put time in front of your crontabs, and if you're getting notifications about cron script outputs, it'll get sent to you.
For example, if you had:
0 1,13 * * * /maint/run_webalizer.sh
add time in front
0 1,13 * * * time /maint/run_webalizer.sh
and you'll get some output that looks like (the "real" is the time you want):
real 3m1.255s
user 0m37.890s
sys 0m3.492s
If you don't get cron notifications, you can just pipe the output to a file.