Read a file and pipe to grep

Question

Wondering if anyone can help me, I'm very rusty with bash and seem to hit a bit of an impasse.

I'm storing a list of strings in a file and would like to read the file and pipe each line returned to grep which in turn searches a directory for files containing the string.

Initially attempt:

cat filename | grep -lr *

However this is not returning any output.

Can anyone give me a bit of steer on how best to approach this?

Answer 1

I would try this.

cat filename | while read line ; do grep -lr "$line" * ; done

You could also pipe it to "sort -u" so you don't get duplicate.

Answer 2

Avoid that useless use of cat. You can of course solve this with xargs and the like. But that's over-complex compared to a simple while loop.

while read i 
do
    grep -r -- "$i" directory/
done < filename