grep Cheat Sheet
# grep Cheat Sheet
## Basic Usage
```
grep "pattern" file.txt
grep -r "pattern" /path/ # Recursive
grep -i "pattern" file.txt # Case insensitive
grep -n "pattern" file.txt # Show line numbers
grep -c "pattern" file.txt # Count matches
```
## Regex
```
grep "^start" file.txt # Line starts with
grep "end$" file.txt # Line ends with
grep "colou?r" file.txt # Optional character
grep -E "cat|dog" file.txt # Extended regex (OR)
grep -P "\d{3}" file.txt # Perl regex
```
## Context
```
grep -A 3 "pattern" file.txt # 3 lines after
grep -B 3 "pattern" file.txt # 3 lines before
grep -C 3 "pattern" file.txt # 3 lines context
```
## Invert
```
grep -v "pattern" file.txt # Lines NOT matching
```
## Common Patterns
```
grep -rn "TODO" src/ # Find TODOs
grep -rn "import.*from" src/ # Find imports
grep -rn "console.log" src/ # Find console logs
```
## Related Tools
- ag (silver searcher) — Faster grep
- rg (ripgrep) — Even faster, respects .gitignore
- fgrep — Fixed strings (no regex)