unix command line ...how to grep and show only file names that contain a string?

Question

I know I can search for a string with:

grep -n -d recurse 'snoopy' *

and then it shows every file name and instance that contains that string, like:

file/name.txt:23    some snoopy here
file/name2.txt:59   another snoopy there
file/name2.txt:343  some more snoopy
etc...

The problem is that with many occurrences, the list is huge. How do I make it show only the actual file names that contain the string, without duplicates and without the occurrence?

Only like:

file/name1.txt
file/name52.txt
file/name28293.txt

Thanks a lot for any help :)

Answer 1

The -l flag (or, in both BSD and GNU grep, --files-with-matches) does what you want.

From the POSIX spec:

Write only the names of files containing selected lines to standard output. Pathnames shall be written once per file searched. If the standard input is searched, a pathname of "(standard input)" shall be written, in the POSIX locale. In other locales, "standard input" may be replaced by something more appropriate in those locales.

Both BSD and GNU also explicitly guarantee that this will be more efficient. (Older BSD versions say "… grep will only search a file until a match has been found, making searches potentially less expensive", newer BSD and GNU say "The scanning will stop on the first match".) If you don't know which grep you have and which options it has, just type man grep at the shell and you should get the manpage.