Grep

Searches input files selecting line to match patterns with

grep [opts] [re] [file]

grep jorge test.txt 
#same as 
grep "jorge" test.txt

Use \ to escape characters

Search Directory

grep -r "\"Help.*me\"" .

Count number of lines with the word test in it

grep -r phone . | wc -l

Some Options

Flag	Does
-o	only print matching part of line
-n	output line #s too
-r	search recursively subdirs
-i	case insensitive
-v	select the non-matching lines
-E	Use extended grep(see below)
-F	Fixed string matching(faster if not re)
-C [n]	n lines shown b4 and after match

Extended Grep

Allows you to do stuff like specific or ranges of repetitions

Not

grep -E "1[^2]" #1 followed by not two

Range

grep -E "a{4}" #4 a's 
grep -E ">[0-9]{10,16}<" #10-16 digit number between > and <

Or

grep -E '(^| )ABC( |$)' file1 #ABC surrounded by a space or ending

Other Tools

https://beyondgrep.com/feature-comparison/

ack, ag, git grep, ripgrep