How to search for a string in multiple files with grep

Find every occurrence of a text pattern across multiple files in a directory tree using grep's -r recursive flag with optional filename and extension filters.

Step-by-Step: Search Multiple Files with grep

1. Search All Files in a Directory Recursively

grep -r "error" /var/log/

The grep -r flag searches every file in /var/log/ and all subdirectories. grep prints each matching line prefixed with the filename.

2. Limit Search to Specific File Extensions

grep -r --include="*.conf" "listen" /etc/nginx/

The --include flag restricts grep to files matching the glob pattern. This searches only .conf files within the Nginx configuration directory.

3. Show Line Numbers and Filenames

grep -rn "404" /var/log/nginx/

The -n flag adds line numbers to grep's output. Combined with -r, each result shows filename:line_number:matching_line.

4. List Only Filenames with Matches

grep -rl "TODO" /home/user/project/

The -l flag tells grep to print only the filenames that contain matches, without showing the matching lines.

Common Issues

grep searches binary files and outputs garbled text— Add --binary-files=without-match or -I to skip binary files. See grep: Binary file matches.