Grep Cheat Sheet

Some quick commands to search for urls, domains, emails, ipv4 addresses and specific file extensions.

Data Type	Command Example	Description
HTTP/HTTPS URLs	grep -oEi 'https?://[^[:space:]]+' file.txt	Matches URLs regardless of capitalization (e.g., HTTP://, https://).
Domains	grep -oEi '([a-zA-Z0-9-]+\.)+[a-zA-Z]{2,}' file.txt	Matches domain names safely across any case variations.
Email Addresses	grep -oEi '[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}' file.txt	Matches email addresses regardless of username or domain case.
IPv4 Addresses	grep -oE '\b([0-9]{1,3}\.){3}[0-9]{1,3}\b' file.txt	Extracts standard IPv4 addresses (e.g., 192.168.1.1).
Given File Extension	grep -oEi '[^[:space:]]+\.(exe|ps1)' file.txt	Matches filenames ending in specific extensions (like .exe or .ps1).

Tip: The -i flag makes the search case-insensitive, while -o prints only the matching text and -E enables extended regular expressions.