Useful grep Snippets

TOC

  1. Useful grep Snippets
  2. TOC
    1. Basic Search
    2. Recursive Search
    3. Pattern Matching
    4. Filter Files
    5. Output Control
    6. Contextual Search
    7. Advanced Usage
    8. Combining with Other Commands
    9. Debugging & Efficiency
  3. Extended grep Snippets
    1. File Type Filtering
    2. Binary Files
    3. Performance Optimizations
    4. POSIX Character Classes
    5. Custom Delimiters
    6. Multiple Patterns
    7. Miscellaneous
    8. Multiline Matching
    9. Using grep with xargs
    10. Combining grep with sed and awk
    11. Environment Variables
    12. Highlight Matches in Less
  1. Find a keyword in files: 
    grep "keyword" filename
  2. Case-insensitive search: 
    grep -i "keyword" filename
  1. Search recursively in all files: 
    grep -r "keyword" /path/to/directory
  2. Search recursively for a pattern while excluding specific directories: 
    grep -r --exclude-dir="dir_to_exclude" "keyword" /path/to/directory

Pattern Matching

  1. Search using regular expressions: 
    grep -E "pattern1|pattern2" filename
  2. Match whole words only: 
    grep -w "word" filename

Filter Files

  1. Find files containing a pattern: 
    grep -l "keyword" /path/to/directory/*
  2. Exclude files with certain extensions: 
    grep --exclude=*.log "keyword" /path/to/files/*

Output Control

  1. Show line numbers with matches: 
    grep -n "keyword" filename
  2. Show only the matched part of the line: 
    grep -o "pattern" filename
  1. Show lines before and after matches: 
    grep -C 3 "keyword" filename  # 3 lines of context
  2. Show only lines before the match: 
    grep -B 3 "keyword" filename
  3. Show only lines after the match: 
    grep -A 3 "keyword" filename

Advanced Usage

  1. Search for patterns in compressed files: 
    zgrep "keyword" file.gz
  2. Count occurrences of a pattern: 
    grep -c "keyword" filename
  3. Invert the match (find lines without the pattern): 
    grep -v "keyword" filename

Combining with Other Commands

  1. Pipe output to grep: 
    ps aux | grep "process_name"
  2. Highlight matches in terminal output: 
    grep --color=always "keyword" filename

Debugging & Efficiency

  1. Display file names along with matches in a directory: 
    grep -H "keyword" /path/to/directory/*
  2. Limit search depth in recursive searches: 
    grep -r --include=*.txt "keyword" --max-depth=2 /path/to/directory

These snippets cover a wide variety of use cases. Let me know if you’d like more examples for specific scenarios!

Extended grep Snippets

File Type Filtering

  1. Search only in specific file types: 
    grep --include=*.{c,h} "keyword" /path/to/directory/*
  2. Exclude specific file types: 
    grep --exclude=*.{log,tmp} "keyword" /path/to/directory/*

Binary Files

  1. Ignore binary files in search: 
    grep --binary-files=without-match "keyword" /path/to/directory/*
  2. Search binary files: 
    grep --binary-files=text "keyword" /path/to/binary_file

Performance Optimizations

  1. Limit output to first N matches: 
    grep -m N "keyword" filename
  2. Search large files without buffering: 
    grep --line-buffered "keyword" largefile

POSIX Character Classes

  1. Search for digits: 
    grep "[[:digit:]]" filename
  2. Search for alphanumeric characters: 
    grep "[[:alnum:]]" filename

Custom Delimiters

  1. Specify output delimiters: 
    grep -z "keyword" filename  # Null-separated output

Multiple Patterns

  1. Search for multiple keywords (logical OR): 
    grep -e "keyword1" -e "keyword2" filename
  2. Search for multiple patterns from a file: 
    grep -f patterns.txt filename

Miscellaneous

  1. Print file offsets of matches: 
    grep -b "keyword" filename
  2. Print the count of matches per file: 
    grep -c "keyword" filename
  3. Suppress error messages: 
    grep "keyword" filename 2>/dev/null

Multiline Matching

  1. Search across multiple lines (using Perl-compatible grep): 
    grep -Pzo "pattern1.*?pattern2" filename

Using grep with xargs

  1. Find files and search within them: 
    find /path/to/search -name "*.txt" | xargs grep "keyword"

Combining grep with sed and awk

  1. Replace pattern in grep results: 
    grep "pattern" filename | sed 's/pattern/replacement/g'
  2. Count and format grep results: 
    grep "pattern" filename | awk '{count++} END {print "Total:", count}'

Environment Variables

  1. Ignore case permanently by setting environment variable: 
    export GREP_OPTIONS='--ignore-case'

Highlight Matches in Less

  1. Search while paging with highlights: 
    grep "keyword" filename | less -R