GREP: Global Regular Expression Print

The grep command is an essential power tool for developers and system administrators. Whether you're searching for patterns in code, filtering through large files, analyzing logs, or parsing output — grep makes it fast and efficient, all within the terminal. Here’s a practical list of its most useful options to make your daily work smoother and smarter.

1. Basic Pattern Matching

grep "error" logfile.txt

Searches for lines containing the word error in logfile.txt.

2. Useful GREP Switches with Examples

🔍 -i — Case Insensitive Search

grep -i "error" app.log

Matches "Error", "ERROR", "eRrOr", etc.

📁 -r or --recursive — Search in Folders

grep -r "function" ./src

Recursively search "function" inside all files under ./src.

🔢 -n — Show Line Numbers

grep -n "TODO" main.py

Shows which line contains the match (useful for debugging).

🚫 -v — Invert Match (Exclude)

grep -v "DEBUG" server.log

Show all lines except those that contain DEBUG.

📄 -l — Show File Names Only

grep -l "connect" *.js

📄 -w — Show exact match

grep -w "kamal" users.csv

List only filenames where the  exact match occurs.

👁️ -A / -B / -C — Show Surrounding Context

grep -A 2 -B 1 "error" logs.txt

Shows 2 lines after and 1 line before each "error" match.

🔁 -E — Use Extended Regex

grep -E "warn|error" logs.txt

Matches "warn" OR "error". Very useful for complex patterns.

📈 -c — Count Matches Only

grep -c "user" users.csv

Just show how many lines contain the word "user".

⚡ --color=auto — Highlight Matches

grep --color=auto "main" app.js

Essential GREP Commands Every Developer Should Know

1. Search a keyword across multiple files

Use grep to search a keyword inside all files of a given type.

grep "error" *.log

2. Suppress file name from output using -h

If you are searching in multiple files but want to hide the filename in the result, use:

grep -h "apple" *.txt

3. Use multiple patterns with egrep or -e

Search for multiple words or expressions in one go:

egrep "apple|banana" fruits.txt

grep -e "apple" -e "banana" fruits.txt

4. Show only file names using -l

Lists only the filenames where the match occurs.

grep -l "password" *.env

5. Search using a file with multiple patterns using -f

Useful when you have a list of search terms saved in a file.

grep -f keywords.txt *.log

6. Use anchors like ^ and $ for precise matching

Use ^ to match the start of a line and $ to match the end.

grep "^Ram" names.txt

grep "abc$" data.txt

7. Quiet mode using -q

Suppress output — useful in scripts to check if match exists.

grep -q "success" result.log

8. Suppress error messages using -s

Ignore permission or missing file errors silently.

grep -s "note" *.txt

9. Check exit code using echo $?

Get the result of last grep: 0 = match, 1 = no match, 2 = error.

grep -q "ready" file.txt
echo $?

10. Case-insensitive file match using pipe and -i

Find files regardless of uppercase or lowercase.

ls | grep -i "report"

Also Useful: awk and sed with Examples

awk: For column-based text extraction

awk is a powerful tool to extract fields or format output.

awk '{ print $2 }' employees.txt

sed: Stream editor to replace text

sed is commonly used to find and replace content within files or pipelines.

sed 's/error/success/g' log.txt

Bonus: Combine grep with Other Commands

ps aux | grep node

Filter system processes to see only Node.js related entries.

Conclusion

In my experience, learning grep properly has saved me countless hours of debugging, searching code, and even monitoring servers. These options aren’t just for sysadmins — they’re for every developer who lives in the terminal. Bookmark this guide or save a cheat sheet, and next time you're lost in a sea of text, let grep do the heavy lifting.

Got a favorite grep trick? Share it in the comments!