Unix / Linux search command utility#

Usage:#

grep [options] regexp  [file...]

Options:

	-v	show lines that don't match instead of lines that match
	-H	print file names with matches
	-i	ignore case
	-E      enable extended regular expressions
	-c      print count only
	-l      just print the names of files that have matches
	-n      print line numbers
	-r      recurse into sub-directories

Regular expressions (extended):#

Matching characters

	.	match any character
	^	matches beginning of line
	$	matches end of line
	[abc]	matches 'a', 'b', or 'c'
	[^abc]	matches anything except 'a', 'b', or 'c'
	[a-e]	range match, same as [abcde]
	[[:x:]]	match pre-difned class of characters as follows:
		:alnum:
		:alpha:
		:digit:
		:lower:
		:upper:
		:space:
	\w	same as [[:alnum:]]
	\W	same as [^[:alnum:]]

Repeating characters

	?	preceding item matched 0 or 1 time
	*	zero or more times
	+	one or more times

        e1|e2   matches expression e1 OR e2