How to generate a file after grep just if it founds the content?

Question

I'm doing this (e.g.:):

grep a text.txt > file.log

I can generate the file.log just if it founds the "a". Should I put it into a if? How? Can someone please give me an example? At this time this is generating blank files.

Answer 1

A simple workaround would be to say:

grep a text.txt > file.log || rm file.log

This would remove file.log if grep didn't find a match. So you won't have blank files.

Answer 2

awk '/a/{print >"file.log"}' text.txt

this command will create file.log if the file text.txt has a match with 'a'