How to search file contents with grep - Rocketeers app [ Rocketeers ](/) [Login](https://rocketeersapp.com/login) On this page Knowledge --------- How to search file contents with grep ===================================== ### [\#CommandLine](https://rocketeersapp.com/knowledge/command-line) Search inside files with grep — recursive search, case-insensitive matching, line numbers, context, regex and piping output from other commands into grep. Published by [Mark van Eijk](https://rocketeersapp.com/author/mark-van-eijk) on June 23, 2026 · 1 minute read 1. [Searching inside files with grep](#content-searching-inside-files-with-grep) 2. [Search recursively](#content-search-recursively) 3. [Case-insensitive matching](#content-case-insensitive-matching) 4. [Show line numbers](#content-show-line-numbers) 5. [Match whole words and invert](#content-match-whole-words-and-invert) 6. [Count matches](#content-count-matches) 7. [Show surrounding context](#content-show-surrounding-context) 8. [Using regular expressions](#content-using-regular-expressions) 9. [Piping into grep](#content-piping-into-grep) [\#](#content-searching-inside-files-with-grep "Permalink")Searching inside files with grep ------------------------------------------------------------------------------------------- While [find](/find-files-linux-command) locates files by their name or metadata, `grep` searches what's *inside* them. It scans for lines matching a pattern and prints them. The basic form is `grep 'pattern' file`: ``` grep 'database' config/app.php ``` [\#](#content-search-recursively "Permalink")Search recursively --------------------------------------------------------------- To search every file under a directory, add `-r` (recursive). This is the one I use most: ``` grep -r 'API_KEY' . ``` [\#](#content-case-insensitive-matching "Permalink")Case-insensitive matching ----------------------------------------------------------------------------- By default grep is case-sensitive. Add `-i` to ignore case, so `Error`, `error` and `ERROR` all match: ``` grep -ri 'todo' src/ ``` [\#](#content-show-line-numbers "Permalink")Show line numbers ------------------------------------------------------------- Add `-n` to prefix each match with its line number, which makes jumping to it in an editor much faster: ``` grep -n 'function' app.js ``` [\#](#content-match-whole-words-and-invert "Permalink")Match whole words and invert ----------------------------------------------------------------------------------- Use `-w` to match a whole word only, so searching `log` won't also match `login` or `catalog`: ``` grep -w 'log' app.php ``` Flip the logic with `-v` to print lines that *don't* match — useful for filtering noise out of a file: ``` grep -v '^#' config.ini ``` That example drops every commented line (those starting with `#`). [\#](#content-count-matches "Permalink")Count matches ----------------------------------------------------- When you only care how many times something appears, `-c` prints the count of matching lines instead of the lines themselves: ``` grep -c 'POST' access.log ``` [\#](#content-show-surrounding-context "Permalink")Show surrounding context --------------------------------------------------------------------------- Sometimes the matching line alone isn't enough. Use `-A` for lines after, `-B` for before, and `-C` for both: ``` grep -C 3 'Exception' storage/logs/laravel.log ``` This prints each match with 3 lines on either side. [\#](#content-using-regular-expressions "Permalink")Using regular expressions ----------------------------------------------------------------------------- The pattern is a regular expression, so you can match more than literal text. Add `-E` for extended regex syntax like alternation and `+`: ``` grep -E 'warning|error|critical' app.log ``` This finds any line containing one of those three words. [\#](#content-piping-into-grep "Permalink")Piping into grep ----------------------------------------------------------- grep really shines at the end of a pipe, filtering the output of another command. This is everyday glue on the command line: ``` ps aux | grep nginx git log --oneline | grep 'fix' ``` Combine these flags freely — for example `grep -rin 'token' .` gives you a recursive, case-insensitive search with line numbers — and grep becomes one of the most useful tools in your kit. ### Subscribe to our newsletter Do you want to receive regular updates with fresh and exclusive content to learn more about web development, hosting, security and performance? Subscribe now! 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