Return a regex match in a Bash script, instead of replacing it

Question

I just want to match some text in a Bash script. I\'ve tried using sed but I can\'t seem to make it just output the match instead of replacing it with something.

Answer 1

Pure Bash. Use parameter substitution (no external processes and pipes):

string="TestT100String"

echo ${string//[^[:digit:]]/}

Removes all non-digits.