awk calculate average or zero

Question

I am calculating the average for a bunch of numbers in a bunch of text files like this:

grep '^num' file.$i | awk '{ sum += $2 } END { print sum / NR }'

But some times the file doesn't contain the pattern, in which cas I want the script to return zero. Any ideas of this slightly modified one-liner?

Answer 1

You're adding to your load (average) by spawning an extra process to do everything the first can do. Using 'grep' and 'awk' together is a red-flag. You would be better to write:

awk '/^num/ {n++;sum+=$2} END {print n?sum/n:0}' file

Answer 2

Try this:

... END { print NR ? sum/NR : 0 }