Sys-Admin

Introduction

Grep is a tool used to search strings.

Application

General commands.

grep [options] 'search_pattern' file

Options -i - case insensitive. -r - search directory recursively. --color -add color to output when using sudo. -v - invert match. words that don’t match. -w - match exact search word. -o - show only matching option. -E - Use extended regex

Show uncomment config lines

grep -vE '^\s*#|^\s*$' /etc/ssh/sshd_config --color

Breakdown:

-v invert match, i.e., exclude lines that match the pattern.
-E use extended regex.
'^\s*#|^\s*$' regex pattern that matches:
- ^\s*#: lines that start with optional whitespace and then a # (comment lines).
- ^\s*$: lines that are completely empty or just whitespace.

So this part removes:

All comments starting with ‘#’.
All blank lines.

Referances

Grep wiki