How to list files that contain a grep match

When a review starts with matching lines, the file names can be the part that matters most. Use grep -l when the handoff needs the files that contain a pattern, not every line that matched inside those files.

The -l option prints each matching file once and stops reading that file after the first match. Combine it with -R when the search should walk below one or more directories.

The sample below uses three small files across separate directories: two mention /login and one does not. The expected proof is that grep -R -l /login app docs tmp lists only the two matching files, while grep -R -L /login app docs tmp lists the file that contains no match.

1. Create a small sample tree with two matching files and one nonmatching file.

   $ mkdir -p app docs tmp
   $ cat > app/routes.conf <<'EOF'
   GET /health status=ok
   POST /login status=requires_auth
   EOF
   $ cat > docs/runbook.md <<'EOF'
   Check /health before rotating workers.
   Run /login tests after deploying auth changes.
   EOF
   $ cat > tmp/cache.txt <<'EOF'
   temporary cache entry
   EOF

2. List only the files that contain the target pattern.

   $ grep -R -l /login app docs tmp
   app/routes.conf
   docs/runbook.md

   grep -l prints file names, not matching lines. Each matching file appears once even if the pattern appears more than once inside it.

3. List files that do not contain the pattern when the review needs the inverse file set.

   $ grep -R -L /login app docs tmp
   tmp/cache.txt

   grep -L is the file-level inverse of -l. It is useful before adding a missing setting or finding files that skipped a required token.

4. Run a second file-name search for a different token to confirm the file list follows the pattern, not the directory names.

   $ grep -R -l /health app docs tmp
   app/routes.conf
   docs/runbook.md

5. Remove the sample tree after testing.

   $ rm -r app docs tmp