Check if a variable has a specific string in it in an if statement

Question

I am trying to check to see if a string exists inside a variable inside an if statement.

if  [ -n $(echo "$RUN" | grep "Done running command.") ]; then

I know this can be done by creating another variable then checking if that is empty but I am trying to see if it can be done in a more streamlined way.

CHK=$(echo "$RUN" | grep "Done running command.")
if  [ -n "$CHK" ]; then

Any incite on this would be helpful.

Answer 1

You can use regex matches, which will save the spawning of a grep command, for a better performance and bash integration:

if [[ "$RUN" =~ "Done running command." ]] ; then echo OK ; fi

(note that if the dot is withing the quotes, it acts as a normal dot, not a wildcard character: that's for the best for our example)

test:

RUN="ok, Done running command. Bye"
OK

RUN="not running command. Bye"
<nothing printed>