Text Manipulation and Grep

Text manipulation is a core skill for log analysis, data extraction, and automation in security work. The combination of grep, sed, awk, and cut forms a powerful text processing pipeline.

Grep options: -i (case insensitive), -r (recursive), -v (invert match), -n (line numbers), -E (extended regex), -A/-B/-C (context lines). Example: grep -E "failed|error|denied" /var/log/auth.log -i extracts authentication failures.

AWK for structured data: awk -F: '{print $1}' /etc/passwd prints all usernames. Sed for substitution: sed 's/old/new/g' file.txt. Cut for column extraction: cut -d: -f1,3 /etc/passwd. Combining these with pipes creates powerful one-liners for rapid data analysis.