Regular Expression Quick Reference
Compiled from numerous sources across the web.
| Quantifiers
|
| * |
0 or more |
| *? |
0 or more, ungreedy |
| + |
1 or more |
| +? |
1 or more, ungreedy |
| ? |
0 or 1 |
| ?? |
0 or 1, ungreedy |
| {3} |
Exactly 3 |
| {3,} |
3 or more |
| {3,5} |
3, 4 or 5 |
| {3,5}? |
3, 4 or 5, ungreedy |
|
| Ranges (inclusive)
|
| . |
Until new line (\n) |
| (a|b) |
a or b |
| (…) |
Group |
| (?:…) |
Passive Group |
| [abc] |
Range (a or b or c) |
| [^abc] |
Not a or b or c |
| [a-q] |
Char between a & q |
| [A-Q] |
Uppercase between A & Q |
| [0-7] |
Digit between 0 & 7 |
| \n |
nth group/subpattern |
|
| POSIX Character Classes
|
| [:upper:] |
Uppercase chars |
| [:lower:] |
Lowercase chars |
| [:alpha:] |
All chars |
| [:alnum:] |
Digits, chars |
| [:digit:] |
Digits |
| [:xdigit:] |
Hex digits |
| [:punct:] |
Punctuation |
| [:blank:] |
Space, tab |
| [:space:] |
Blank chars |
| [:cntrl:] |
Control chars |
| [:graph:] |
Printed chars |
| [:print:] |
Printed chars, spaces |
| [:word:] |
Digits, chars, underscores |
|
| Character Classes
|
| \c |
Control char |
| \s |
Whitespace |
| \S |
Not whitespace |
| \d |
Digit |
| \D |
Not digit |
| \w |
Word |
| \W |
Not word |
| \xhh |
Hex char hh |
| \Oxxx |
Octal char xxx |
| Metachars (must be escaped)
|
| [ ] { } ( ) < > |
| \ | ^ $ . * + ? |
|
| String Replacement (backreferences)
|
| $n |
nth non-passive group |
| 2 |
xyz in /^(abc(xyz))$/ |
| 1 |
xyz in /^(?:abc)(xyz)$/ |
| $` |
Before matched string |
| $’ |
After matched string |
| $+ |
Last matched string |
| $& |
Entire matched string |
| $_ |
Entire input string |
| $$ |
Literal “$” |
|
| Anchors
|
| ^ |
Start of line |
| \A |
Start of string |
| $ |
End of line |
| \Z |
End of string |
| \b |
Word boundary |
| \B |
Not word boundary |
| \< |
Start of word |
| \> |
End of word |
|
| Assertions
|
| ?= |
Lookahead assertion |
| ?! |
Negative lookahead |
| ?<= |
Lookbehind assertion |
| ?!= or ?
| Negative lookbehind |
| ?> |
Once-only Subexpression |
| ?() |
Condition [if then] |
| ?()| |
Condition [if then else] |
| ?# |
Comment |
|
| Special Characters
|
| \ |
Escape Character |
| \n |
New line |
| \r |
Carriage return |
| \t |
Tab |
| \v |
Vertical tab |
| \f |
Form feed |
| \a |
Alarm |
| [\b] |
Backspace |
| \e |
Escape |
| \N{name} |
Named Character |
|
| Pattern Modifiers
|
| g |
Global match |
| i |
Case-insensitive |
| m |
Multiple lines |
| s |
Treat string as single line |
| x |
Allow comments & whitespace |
| e |
Evaluate replacement |
| U |
Ungreedy pattern |
| Samples
|
| \d{1,2}\/\d{1,2}\/\d{4} |
| Date e.g. 12/22/1974 |
| [^\s]+(?=\.(jpg|gif|png))\.\2 |
| filename with extension jpg, gif or png |
| ^[1-9]{1}$|^[1-4]{1}[0-9]{1}$|^50$ |
| any number from 1 to 50 |
| #?([A-Fa-f0-9]){3}(([A-Fa-f0-9]){3})? |
| hexadecimal color code |
| (?=.*\d)(?=.*[a-z])(?=.*[A-Z]).{8,16} |
| 8 to 16 char string with uppercase, lower case, & one digit (for passwords) |
| \w+@[a-zA-Z_]+?\.[a-zA-Z]{2,6} |
| email addresses |
| \<(/?[^\>]+)\> |
| HTML Tags |
| [a-zA-Z]+://([.]?[a-zA-Z0-9_/-])* |
| Hyperlinks |
