used mostly to apply an ex-style regexp substitution to a file
(very much like applying ex commands in vim, just right from bash)

EXAMPLES
	sed "s/foo/bar/g" file.txt
		replace foo with bar globally in file.txt
	sed "/^foo/d" file.txt
		delete all lines in file.txt that start on foo
	sed -E "s/\s/\n/g" file.txt
		replace all whitespace in file.txt with \n

FLAGS
	-i	change file in place
	-E	use extended regexp
