Regular Expression Syntax cheat sheet.
Published:| Expression | Description | Examples and expansions |
|---|---|---|
| Single character expressions | ||
| . | any single character | spi.e matches "spice", "spike", etc. |
| \char |
for a nonalphanumerical char, matches char literally |
\* matches "*" |
| \n | new line character | |
| \r | carriage return character | |
| \t | tab character | |
| [...] | any single character listed in the brackets | [abc] matches "a", "b", or "c" |
| [...-...] | any single character in the range | [0-9] matches "0" or "1" ... or "9" |
| [^...] | any single character not listed | [^sS] matches one character that is neither "s" nor "S" |
| [^...-...] | any single character not in the range | [^A-Z] matches one character that is not an uppercase letter |
| Anchors/Expressions which match positions | ||
| ^ | beginning of the line | |
| $ | end of the line | |
| \b | word boundary | nt\b matches "nt" in "paint" but not in "pants" |
| \B | word non-boundary | all\B matches "all" in "ally" but not in "wall" |
| Counters/Expressions which quantify previous expressions | ||
| * | zero or more of previous r.e. | a* matches "", "a", "aa", "aaa",... |
| + | one or more of previous r.e. | a+ matches "a", "aa", "aaa",... |
| ? | exactly one or zero of previous r.e. | colou?r matches "color" or "colour" |
| {n} | n of previous r.e. | a{4} matches "aaaa" |
| {n,m} | from n to m of previous r.e. | |
| {n,} | at least n of previous r.e. | |
| .* | any string of characters | |
| (...) |
grouping for precedence and memory for backreference |
|
| ...|... | matches either of neighbor r.e.s | (dog)|(cat) matches "dog" or "cat" |
| Shortcuts | ||
| \d | any digit | [0-9] |
| \D | any non-digit | [^0-9] |
| \w | any alphanumeric/underscore | [a-zA-Z0-9_] |
| \W | any non-alphanumeric | [^a-zA-Z0-9_] |
| \s | whitespace (space, tab) | [\r\t\n\f] |
| \S | non-whitespace | [^\r\t\n\f] |
This cheat-sheet table is from the book Speech and language processing by Daniel Jurafsky & James H. Martin.