How to check if a line exists in a file in a bash script?

Question

linux

It is necessary, if there is no line in the config, add it. How to check for the presence of a line in a file using a bash script?

Answer 1

Well, it's just...

#!/bin/bash
if grep -q myParam myConfigFile
  then echo "myParam string exist!"
else
 echo "Did not find string, adding"
echo "myParam = 0" >> myConfigFile
fi

Answer 2

sed