How to check if a string contains a substring in Bash

Question

I have a string in Bash:

string=\"My string\"

How can I test if it contains another string?

if [ $string ?? \'foo\' ]; then         


        

Answer 1

I like sed.

substr="foo"
nonsub="$(echo "$string" | sed "s/$substr//")"
hassub=0 ; [ "$string" != "$nonsub" ] && hassub=1

Edit, Logic:

• Use sed to remove instance of substring from string

• If new string differs from old string, substring exists