Grep

-E - extended regex

-i - ignore case sensitive

-v - invert match

-c - count

-o - only the matching part

-q - doesnt print the result, sets the exits status



Sed

sed s/*replace*/*with*/gi *file*

	s - replaces x with y

	g - replaces all (global)
	i - case insensitive

sed y/*replace*/*with*/ *file*

	y - replace x[i] with y[i]


sed /*to_delete*/d

	d - delete


Awk

NR - number of current line
NF - number of fields on the current ine
$0 - whole line
$1 - field 1

awk -F '{*code*}' *file*


-F -specifie delimitor

code:
	BEGIN {*before*}
	{*for each line*}
	END{*after*}