Cheat Sheet #day43 - grep

grep Cheatsheet

Basic Usage

• Search for a Pattern in a File

    grep 'pattern' filename
  

• Search for a Pattern in Multiple Files

    grep 'pattern' file1 file2 file3
  

Common Options

• Ignore Case Sensitivity

    grep -i 'pattern' filename
  

• Show Line Numbers

    grep -n 'pattern' filename
  

• Search Recursively in Directories

    grep -r 'pattern' directory
  

• Show Only Matching Part of the Line

    grep -o 'pattern' filename
  

• Count the Number of Matches

    grep -c 'pattern' filename
  

• Show Lines that Do Not Match the Pattern

    grep -v 'pattern' filename
  

Advanced Options

• Search for Whole Words

    grep -w 'pattern' filename
  

• Match the Pattern at the Beginning of a Line

    grep '^pattern' filename
  

• Match the Pattern at the End of a Line

    grep 'pattern$' filename
  

• Show N Lines of Context Before the Match

    grep -B N 'pattern' filename
  

• Show N Lines of Context After the Match

    grep -A N 'pattern' filename
  

• Show N Lines of Context Around the Match

    grep -C N 'pattern' filename
  

Useful Tips

• Use Extended Regular Expressions

    grep -E 'pattern' filename
  

• Use Fixed Strings (Faster for Simple Strings)

    grep -F 'pattern' filename
  

• Show Only the Names of Files with Matches

    grep -l 'pattern' filename
  

• Show Only the Names of Files without Matches

    grep -L 'pattern' filename
  

• Display Help for grep

    grep --help
  

• Search Using Perl-Compatible Regular Expressions

    grep -P 'pattern' filename
  

• Colorize the Output

    grep --color=auto 'pattern' filename
  

Examples

• Search for a Case-Insensitive Pattern in a File

    grep -i 'error' logfile.txt
  

• Search for a Pattern in All Files in the Current Directory

    grep 'TODO' *
  

• Search for a Pattern Recursively in a Directory

    grep -r 'TODO' /path/to/directory
  

• Search for a Whole Word Only

    grep -w 'hello' filename
  

• Search for a Pattern and Show Line Numbers

    grep -n 'main' script.py
  

• Search for a Pattern and Show Only Matching Part of the Line

    grep -o 'http[s]*://[^ ]*' filename
  

• Count the Number of Occurrences of a Pattern

    grep -c 'main' script.py
  

• Search for a Pattern and Show 3 Lines of Context After the Match

    grep -A 3 'function' script.py
  

• Search for a Pattern and Show 2 Lines of Context Before the Match

    grep -B 2 'error' logfile.txt
  

• Search for a Pattern and Show 1 Line of Context Around the Match

    grep -C 1 'TODO' script.py
  

• Use Extended Regular Expressions to Search for Multiple Patterns

    grep -E 'error|warning|info' logfile.txt
  

• Search for a Pattern Using Perl-Compatible Regular Expressions

    grep -P '\d{3}-\d{2}-\d{4}' filename
  

• Search for a Pattern in a Compressed File

    zgrep 'pattern' file.gz
  

This cheatsheet covers essential commands and options for using grep effectively, from basic searching to advanced pattern matching and context display. Adjust the commands according to your specific requirements and environment.