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Regex
Platforma testująca: https://regexr.com/
Metacharacters
Metacharacters are characters with a special meaning:
| Character | Description | Example |
|---|---|---|
[] | A set of characters | [a-m] |
\ | Signals a special sequence (can also be used to escape special characters) | \d |
. | Any character (except newline character) | he..o |
^ | Starts with | ^hello |
$ | Ends with | planet$ |
* | Zero or more occurrences | he.*o |
+ | One or more occurrences | he.+o |
? | Zero or one occurrences | he.?o |
{} | Exactly the specified number of occurrences | he.{2}o |
| | Either or | falls|stays |
() | Capture and group | |
Brackets
Brackets are used to find a range of characters:
| Bracket | Description |
|---|---|
[abc] | Find any character between the brackets |
[^abc] | Find any character NOT between the brackets |
[0-9] | Find any character between the brackets (any digit) |
[^0-9] | Find any character NOT between the brackets (any non-digit) |
(x|y) | Find any of the alternatives specified |
Special Sequences
A special sequence is a \ followed by one of the characters in the list below, and has a special meaning:
| Character | Description | Example |
|---|---|---|
\A | Returns a match if the specified characters are at the beginning of the string | \AThe |
\b | Returns a match where the specified characters are at the beginning or at the end of a word (the „r” in the beginning is making sure that the string is being treated as a „raw string”) | \bain ain\b |
\B | Returns a match where the specified characters are present, but NOT at the beginning (or at the end) of a word (the „r” in the beginning is making sure that the string is being treated as a „raw string”) | \Bain ain\B |
\d | Returns a match where the string contains digits (numbers from 0-9) | \d |
\D | Returns a match where the string DOES NOT contain digits | \D |
\s | Returns a match where the string contains a white space character | \s |
\S | Returns a match where the string DOES NOT contain a white space character | \S |
\w | Returns a match where the string contains any word characters (characters from a to Z, digits from 0-9, and the underscore _ character) | \w |
\W | Returns a match where the string DOES NOT contain any word characters | \W |
\Z | Returns a match if the specified characters are at the end of the string | Spain\Z |
Sets
A set is a set of characters inside a pair of square brackets [] with a special meaning:
| Set | Description |
|---|---|
[arn] | Returns a match where one of the specified characters (a, r, or n) is present |
[a-n] | Returns a match for any lower case character, alphabetically between a and n |
[^arn] | Returns a match for any character EXCEPT a, r, and n |
[0123] | Returns a match where any of the specified digits (0, 1, 2, or 3) are present |
[0-9] | Returns a match for any digit between 0 and 9 |
[0-5][0-9] | Returns a match for any two-digit numbers from 00 and 59 |
[a-zA-Z] | Returns a match for any character alphabetically between a and z, lower case OR upper case |
[+] | In sets, +, *, ., |, (), $, {} has no special meaning, so [+] means: return a match for any + character in the string |