Finding Needles in Haystacks
grep (Globally search a Regular Expression and Print) is the fundamental tool for searching plain text data, usually receiving its input via a pipe.
Syntax
grep [options] pattern [file...]
Basic Searching
Find all lines in /etc/passwd that contain the username jsmith:
bash $ grep jsmith /etc/passwd jsmith:x:1001:1001:John Smith:/home/jsmith:/bin/bash
Using grep with Pipes
Find all processes currently running that contain 'apache':
bash $ ps aux | grep apache
Ignoring Case (-i)
The -i option makes the search case-insensitive.
bash $ grep -i root /etc/passwd