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65 lines
2.1 KiB
Markdown
65 lines
2.1 KiB
Markdown
# Common Regex Syntax
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## Character Types
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`\d` any digit (0-9)
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`\D` any non digit character
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`\s` whitespace (space, tab, new line)
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`\S` any non whitespace charaters
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`\w` any alphanumeric charater (a-z, A-Z)
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`\W` any non alphanumeric character
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`\b` whitespace surrounding words (only at row start or end)
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`\B` whitespace surrounding words (not at row start or end)
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`\A` search only at string start
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`\Z` search only at string end
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`.` any charaters but newline (CRLF, CR, LF)
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## Quantifiers
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`+` one or more repetitions
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`*` zero or more repetitions
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`?` zero or one repetition
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`{m}` exactly *m* times
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`{m, n}` at least *m* times, at most *n* times
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The `*`, `x`, and `?` qualifiers are all greedy; they match as much text as possible
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Adding `?` *after* the qualifier makes it perform the match in non-greedy or minimal fashion; as few characters as possible will be matched.
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## Special Characters
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`\a, \b, \f, \n, \r, \t, \u, \U, \v, \x, \\, \?, \*, \+ , \., \^, \$` special characters
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`\(`, `\)`, `\[`, `\]` brackets escaping
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## Delimiters
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`^` match must be at start of string/line
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`$` match must be at end of string/line
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`^__$` match must be whole string
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## Character classes
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`[__]` one of the charaters in the class (`[ab]` --> a or b)
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`[__]{m , n}` consecutive characters in the class (`[aeiou]{2}` --> ae, ao, ...)
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`[a-z]` sequence of lowercase characters
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`[A-Z]` sequence of uppercase characters
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`[a-zA-Z]` sequence of lowercase or uppercase characters
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`[a-z][A-Z]` sequence of lowercase characters followed by sequence of uppercase charaters
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`[^__]` anything but the elements of the class (include `\n` to avoid matching line endings)
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`^`, `\`, `-` and `]` must be escaped to be used in clases: `[ \]\[\^\- ]`
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## Groups
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`(__)` REGEX subgroup
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`(REGEX_1 | REGEX_2)` match in multiple regex (R1 OR R2)
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`(?=__)` match only if `__` is next substring
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`(?!__)` match only if `__` is not next substring
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`(?<=__)` match only if `__` is previous substring
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`(?<!__)` match only if `__` is not previous substring
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`\<number>` refers to n-th group
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## Special Cases
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`(.*)` match anything
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`(.*?)` match anything, non-greedy match
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