grep

Search text files and streams for lines that match a pattern.

Version 2.6.0-FreeBSD Updated 2026-10-14

grep prints every input line that matches a pattern. It reads named files or standard input, so it works equally well at the end of a pipeline. The cards were checked against macOS grep, which aims for GNU compatibility; differences are noted.

Basic searches

Find a word #

grep timeout config.yaml
grep -n 'listen' nginx.conf
ps aux | grep -i postgres

-n prefixes line numbers; -i ignores case.

Match precisely #

Option	Meaning
`-w`	Match whole words only
`-x`	Match whole lines only
`-F`	Treat the pattern as a fixed string
`-v`	Print lines that do not match

Several patterns #

grep -e error -e warning app.log
grep -f patterns.txt app.log

Each -e adds a pattern; -f reads one pattern per line.

Patterns starting with a dash #

Tip

grep -e '--verbose' notes.md
grep -- '-v' notes.md

Regular expressions

Pick a syntax #

Option	Meaning
`-G`	Basic regular expressions (default)
`-E`	Extended: `+`, `?`, `\|` and `()` without backslashes
`-F`	No regex; literal text

Extended examples #

grep -E '^(GET|POST) /api/' access.log
grep -E '[0-9]{3}-[0-9]{4}' contacts.txt
grep -E 'colou?r' style-guide.md

Quote patterns in single quotes so the shell leaves |, * and $ alone. More syntax is on the regex sheet.

Print only the match #

grep -oE '[a-z0-9.]+@example\.org' users.csv

-o prints each matching part on its own line.

Perl syntax #

Note

macOS grep 2.6.0 has no -P option. Use -E, or a grep build that documents -P, for lookarounds and \d.

Files and directories

Search a tree #

grep -rn 'TODO' src/
grep -rn --include '*.go' 'context.TODO' .
grep -rn --exclude-dir vendor --exclude-dir .git 'panic(' .

-r recurses into directories; --include and --exclude take file-name globs.

Only file names #

Option	Meaning
`-l`	Names of files with at least one match
`-L`	Names of files without a match
`-h`	Omit file names from matching lines
`-H`	Always show file names

Binary files #

grep -I -r 'secret' .
grep -a 'marker' dump.bin

-I skips binary files; -a treats them as text.

Context and counting

Surrounding lines #

Option	Meaning
`-A 3`	Three lines after each match
`-B 2`	Two lines before each match
`-C 2`	Two lines on both sides

Count and stop #

grep -c 'ERROR' app.log
grep -m 1 '^version' package.toml

-c counts matching lines per file; -m stops after that many matches.

Use in scripts #

if grep -q '^ENABLE_CACHE=1$' .env; then
  echo "cache on"
fi

-q prints nothing; exit status is 0 on a match, 1 on no match and above 1 on errors.

Highlight matches #

grep --color=auto -n 'deadline' plan.md