Grep

In DE_Tools see: https://github.com/rhyslwells/DE_Tools/blob/main/DE_Tools/Explorations/Other/Terminal/Grep

Example of what Grep can do

1. Search for a pattern in files

grep "error" logfile.txt

• Searches for the word "error" in logfile.txt.
• Useful for quickly checking logs or documents.

2. Recursive search in directories

grep -r "TODO" ./src

• Recursively searches all files in the ./src directory for "TODO".
• Useful for finding code comments, notes, or markers across a codebase.

3. Display line numbers of matches

grep -n "fail" test_results.txt

• Shows line numbers where "fail" appears.
• Helpful for debugging or jumping to the right place in a large file.

4. Show only matching part of the line

grep -o "http[s]\?://[a-zA-Z0-9./?=_-]*" webpage.html

• -o prints only the matching substring (e.g., all URLs from HTML).
• Good for extracting emails, URLs, etc.

5. Search multiple files and include filenames

grep "password" *.conf

• Searches all .conf files and prints matching lines with their filenames.
• Useful for auditing sensitive configurations.

Flags

Useful for finding where a function is used in a code base.

Flag	Description
-w	Match whole words only (ignores substrings).
-i	Perform a case-insensitive match.
-n	Show line numbers of matching lines.
-r	Recursively search subdirectories.
-l	List only filenames that contain matches (no line content shown).
-c	Count matches per file, instead of showing them.
-A N	Show N lines after each match.
-B N	Show N lines before each match.
-C N	Show N lines before and after each match (context lines).
-P	Use Perl-compatible regular expressions (PCRE).
-v	Invert match: show lines that do not match the pattern.
-o	Print only the matching part of the line (not the entire line).
--color	Highlight matched strings with color (if supported by terminal).
--include	Include only files that match the given glob pattern (used with -r).
--exclude	Exclude files that match the given pattern from recursive searches.