GREP

Commands

	Matching Control
`-i`	Ignore case
`-w`	Whole word
`-o`	Print only matched parts
`-m`	Max count
`-a`	Treat binary as text

	Output Control
`-l`	List files
`-h`	No file name
`-o`	Print only matched parts
`-A N`	N lines after
`-B N`	N lines before
`-C N`	N lines before, after
`--line-buffered`	Line buffering on output

File Selection
`--include=".hpp" --include=".cpp"`
`--exclude=".log" --exclude=".md"`
`--exclude-dir="src"`

Perl Regex

  
grep -P

	Class
`.`	Any
`\d`	Digit
`\D`	Negated of digit
`\w`	Word `[0-9a-zA-Z_]`
`\W`	Negated of word
`\s`	Whitespace
`\s`	Negated of whitespace
`[abc]`	Character class [a,b,c]
`^[abc]`	Negated of [a,b,c]
`^`	Begin of line
`$`	End of line
`\`	Escape next character

	Group
`(a\|b)c`	Match ab, ac

	Quantity
`*`	0-N
`?`	0-1
`+`	1-N
`a{2}`	aa
`a{2,4}`	aa - aaaa

	Greedy
`a*b`	Longest a*b
`a*?b`	Shortest a*b

	Boundary
`hello`	`.hello.`
`\bhello\b`	`hello`
`\Bhello\B`	`\whello\w`

		Lookahead
Positive	`car (?=run)`	Match `car` only if followed by `run`	`car run`
Negative	`car (?!run)`	Match `car` only if not followed by `run`	`car stop`

		Lookbehind
Positive	`(?<=red) car`	Match `car` only if preceded by `red`	`red car`
Negative	`(?<!red) car`	Match `cat` only if not preceded by `red`	`blue car`