Linux /bin/sh check if string contains X

Question

In a shell script, how can I find out if a string is contained within another string. In bash, I would just use =~, but I am not sure how I can do the same in /bin/sh. Is i

Answer 1

You can define a function

matches() {
    input="$1"
    pattern="$2"
    echo "$input" | grep -q "$pattern"
}

to get regular expression matching. Note: usage is

if matches input pattern; then

(without the [ ]).