Searching for a variable string from a file with grep

Question

I tried now for a while to

• read from a file test.txt (which has two lines "aaaa" and "bbbb")
• take these lines to search the strings within a folder and its subfolders

My solution looks like this:

while read line 
do echo $line
    grep -irl $line /home 2>/dev/null
done < test.txt

If I replace $line with aaaa it finds the files where aaaa is written in, with $line it doesn't work...?

Maybe you have an idea?

Answer 1

The grep utility has a -f option whose argument is the name of a file. -f tells grep to read patterns from the specified file and then search for all of them, just as if those patterns had been individually specified on the command line. It combines with other options like -r.

-f is specified by POSIX.

GNU Grep allows the file to be specified as -, so the patterns are read from standard input; POSIX says that only file arguments may be specified as - for standard input; no such thing is required for pattern_file arguments.

If the lines of the search file are meant to be strings to look for in the input, as opposed to regular expressions, add the -F option (for fixed-string).