Regular expression cheat sheet

Regular expression crash course

Most frequently used

Flag	Description
g	Find every instance of pattern
i	Case insensitive
m	Multiline

Character	Description
|	Or condition
.	Any single character except newline
+	Any single character/group to the left repeats one or more time
*	Any single character/group to the left repeats zero or more time
{exact}	Exact length of character/group to the left
{min,}	Min length of character/group to the left
{min,max}	Min length and maximum length of character/group to the left
?	Any single character/group to the left is optional
\	Use next character literally i.e. { } [ ] / \ + * . $ ^ | ?
^	Starting with next
$	ending with before

Character Set	Description
[]	Any single character from inside brackets
[x-y]	Ranges start value - end value e.g.[a-zA-Z0-9], [0-3]
[^]	Inverse of character set inside brackets
()	Character group. e.g. (abc) abc in that exact order
\w	Any alphanumeric character and underscore [a-zA-Z0-9_]
\W	Inverse of \w i.e. [^\w]
\d	Any number character i.e. [0-9]
\D	Inverse of \d i.e. [^\d]
\s	Any whitespace [\t\n\f\r]
\S	Inverse whitespace [^\s]

Lazy or Greedy	Description
.* .+	Greedy
.*? .+?	Lazy

Look around	Description
(?=)	Positive lookahead
(?!)	Negative lookahead
(?<=)	Positive lookbehind
(?<!)	Negative lookbehind