nvstrings Regex Features¶
This page will specify which regex features are currently supported by nvstrings. The details are based on features documented at https://www.regular-expressions.info/reference.html
Features Supported¶
Characters¶
| Feature | Syntax | Description | Example |
|---|---|---|---|
| Literal character | Any character except [\^$.|?*+() | All characters except the listed special characters match a single instance of themselves | a matches a |
| Literal curly braces | { and } | { and } are literal characters, unless they're part of a valid regular expression token such as a quantifier {3} | { matches { |
| Backslash escapes a metacharacter | \ followed by any of [\^$.|?*+(){} | A backslash escapes special characters to suppress their special meaning | \* matches * |
| Hexadecimal escape | \xFF where FF are 2 hexadecimal digits | Matches the character at the specified position in the code page | \xA9 matches © |
| Character escape | \n, \r and \t | Match an LF character, CR character and a tab character respectively | \r\n matches a Windows CRLF line break |
| Character escape | \a | Match the "alert" or "bell" control character (ASCII 0x07) | |
| Character escape | \f | Match the "form feed" control character (ASCII 0x0C) | |
| NULL escape | \0 | Match the NULL character | |
| Octal escape | \100 through \177 \200 through \377 \01 through \07 \010 through \077 |
Matches the character at the specified position in the ASCII table | \100 matches @ |
Basic Features¶
| Feature | Syntax | Description | Example |
|---|---|---|---|
| Dot | . (dot) | Matches any single character except line break characters. Optionally match line break characters. | . matches x or (almost) any other character |
| Alternation | | (pipe) | Causes the regex engine to match either the part on the left side, or the part on the right side. Can be strung together into a series of alternatives. | abc|def|xyz matches abc, def or xyz |
Character Classes¶
| Feature | Syntax | Description | Example |
|---|---|---|---|
| Character class | [ | [ begins a character class. | |
| Literal character | Any character except \^-]\ | All characters except the listed special characters are literal characters that add themselves to the character class. | [abc] matches a, b or c |
| Backslash escapes a metacharacter | \ (backslash) followed by any of \^-]\ | A backslash escapes special characters to suppress their special meaning. | [\^\]] matches ^ or ] |
| Range | - (hyphen) between two tokens that each specify a single character. | Adds a range of characters to the character class. | [a-zA-Z0-9] matches any ASCII letter or digit |
| Negated character class | ^ (caret) immediately after the opening [ | Negates the character class, causing it to match a single character not listed in the character class. | [\^a-d] matches x (any character except a, b, c or d) |
| Literal opening bracket | [ | An opening square bracket is a literal character that adds an opening square bracket to the character class. | [ab[cd]ef] matches aef], bef], [ef], cef], and def] |
| Character escape | \n, \r and \t | Add an LF character, a CR character, or a tab character to the character class, respectively. | [\n\r\t] a line feed, a carriage return, or a tab. |
| Character escape | \a | Add the "alert" or "bell" control character (ASCII 0x07) to the character class. | [\a\t] matches a bell or a tab character. |
| Character escape | \b | Add the "backspace" control character (ASCII 0x08) to the character class. | [\b\t] matches a backspace or a tab character. |
| Character escape | \f | Add the "form feed" control character (ASCII 0x0C) to the character class. | [\f\t] matches a form feed or a tab character. |
Shorthand Character Classes¶
| Feature | Syntax | Description | Example |
|---|---|---|---|
| Shorthand | Any shorthand outside character classes | Shorthands can be used outside character classes. | \w matches a single word character |
| Shorthand | \d | Adds all digits to the character class. Matches a single digit if used outside character classes. | \d match a character that is a digit |
| Shorthand | \w | Adds all word characters to the character class. Matches a single word character if used outside character classes. | \w match any single word character |
| Shorthand | \s | Adds all whitespace to the character class. Matches a single whitespace character if used outside character classes. | \s match any single whitespace character |
| Shorthand | Any shorthand inside a character class | Shorthands can be used inside character classes. | [\w] matches a single word character |
| Shorthand | Any negated shorthand inside a character class | Negated shorthands can be used inside character classes. | [\W] matches a single character that is not a word character |
Anchors¶
| Feature | Syntax | Description | Example |
|---|---|---|---|
| String anchor | ^ (caret) | Matches at the start of the string the regex pattern is applied to. | ^. matches a in abc\ndef |
| String anchor | $ (dollar) | Matches at the end of the string the regex pattern is applied to. | .$ matches f in abc\ndef |
| Line anchor | ^ (caret) | Matches after each line break in addition to matching at the start of the string, thus matching at the start of each line in the string. ('m' mode) | ^. matches a and d in abc\ndef |
| Line anchor | $ (dollar) | Matches before each line break in addition to matching at the end of the string, thus matching at the end of each line in the string. ('m' mode) | .$ matches c and f in abc\ndef |
| String anchor | \A | Matches at the start of the string the regex pattern is applied to. | \A\w matches only a in abc |
| String anchor | \Z | Matches at the end of the string the regex pattern is applied to. | \w\Z matches f in abc\ndef but fails to match abc\ndef\n or abc\ndef\n\n |
Word Boundaries¶
| Feature | Syntax | Description | Example |
|---|---|---|---|
| Word boundary | \b | Matches at a position that is followed by a word character but not preceded by a word character, or that is preceded by a word character but not followed by a word character. | \b. matches a, , and d in abc def |
| Word boundary | \B | Matches at a position that is preceded and followed by a word character, or that is not preceded and not followed by a word character. | \B. matches b, c, e, and f in abc def |
Quantifiers¶
| Feature | Syntax | Description | Example |
|---|---|---|---|
| Greedy quantifier | ? (question mark) | Makes the preceding item optional. Greedy, so the optional item is included in the match if possible. | abc? matches abc or ab |
| Greedy quantifier | * (star) | Repeats the previous item zero or more times. Greedy, so as many items as possible will be matched before trying permutations with less matches of the preceding item, up to the point where the preceding item is not matched at all. | ".*" matches "def" "ghi" in abc "def" "ghi" jkl |
| Greedy quantifier | + (plus) | Repeats the previous item once or more. Greedy, so as many items as possible will be matched before trying permutations with less matches of the preceding item, up to the point where the preceding item is matched only once. | ".+" matches "def" "ghi" in abc "def" "ghi" jkl |
Groups¶
| Feature | Syntax | Description | Example |
|---|---|---|---|
| Capturing group | (regex) | Parentheses group the regex between them. They capture the text matched by the regex inside them into a numbered group. They allow you to apply regex operators to the entire grouped regex. | (abc|def)ghi matches abcghi or defghi |
| Non-capturing group | (?:regex) | Non-capturing parentheses group the regex so you can apply regex operators, but do not capture anything. | (?:abc|def)ghi matches abcghi or defghi |