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grep command

Search text for lines that match a pattern.

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Syntax

grep [options] pattern [file…]

Provided by the grep package. Run man grep for the full manual.

Common options

OptionWhat it does
-iIgnore case
-rSearch directories recursively
-nShow line numbers
-vShow lines that don't match
-wMatch whole words only
-cCount matching lines
-lOnly list file names with a match
-EExtended regex (|, +, ? without escaping)
-oPrint only the matched part
-A N / -B N / -C NShow N lines after / before / around each match
--include=GLOBOnly search matching file names

Examples

  1. Search a file

    grep "error" /var/log/syslog

  2. Ignore case

    grep -i "warning" app.log

  3. Search a directory recursively

    grep -rn "DB_PASSWORD" /var/www/

  4. Only list files that match

    grep -rl "TODO" src/

  5. Lines that do not match

    grep -v "^#" /etc/ssh/sshd_config

  6. Count matches

    grep -c "404" access.log

  7. Several words at once

    grep -E "error|fail|critical" app.log

  8. Show 3 lines around each match

    grep -C 3 "Exception" app.log

  9. Only in .php files

    grep -rn --include="*.php" "mysqli_connect" .

  10. Remove comments and blank lines

    grep -Ev "^\s*(#|$)" nginx.conf

  11. Print only the matched text

    grep -oE "[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+" access.log

Tips

  • egrep is the same as grep -E and is deprecated.

grep guides

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