The GREP Command – Complete Guide
GREP is a Unix/Linux command used to search text for patterns using regular expressions.
It prints only the lines that match.
grep "pattern" fileExamples:
grep "error" log.txt grep -i "error" log.txt grep -n "main" source.c
- -i → ignore case
- -r → recursive
- -n → line numbers
- -c → count
- -v → invert match
- -w → whole word
grep "^root" /etc/passwd
grep "[0-9]\{3\}" file
grep -E "error|fail|panic" log.txt
Find failed SSH logins:
grep "Failed password" /var/log/auth.logFind function references:
grep -r "initDatabase" src/
• Insanely fast (written in C)
• Handles massive files
• Full regex engine
• Always installed
• Foundation of shell pipelines
grep is the backbone of Unix search.
• Handles massive files
• Full regex engine
• Always installed
• Foundation of shell pipelines
grep is the backbone of Unix search.