92 lines
3.2 KiB
Markdown
92 lines
3.2 KiB
Markdown
---
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title: regexp
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category: Others
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weight: -1
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authors:
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- github: rizqyhi
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- github: izzergh
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- github: kolapsys
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- github: samtrion
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updated: 2020-03-10
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description: |
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Basic cheatsheets for regular expression
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---
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## RegExp
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{: .-three-column}
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### Character classes
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| Pattern | Description |
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| ------------- | ---------------------------------------- |
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| `.` | Any character, except newline |
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| `\w` | Word |
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| `\d` | Digit |
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| `\s` | Whitespace |
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| `\W` | Not word |
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| `\D` | Not digit |
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| `\S` | Not whitespace |
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| `[abc]` | Any of a, b, or c |
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| `[a-e]` | Characters between `a` and `e` |
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| `[1-9]` | Digit between `1` and `9` |
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| `[[:print:]]` | Any printable character including spaces |
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| `[^abc]` | Any character except `a`, `b` or `c` |
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### Anchors
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| Pattern | Description |
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| ------- | ---------------------- |
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| `\G` | Start of match |
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| `^` | Start of string \* |
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| `$` | End of string \* |
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| `\A` | Start of string |
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| `\Z` | End of string |
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| `\z` | Absolute end of string |
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| `\b` | A word boundary |
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| `\B` | Non-word boundary |
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| `^abc` | Start with `abc` |
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| `abc$` | End with `abc` |
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For multiline patterns (`m` flag), `^` and `$` will act as start and end of line.
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### Escaped characters
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| Pattern | Description |
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| ---------- | -------------------------------------- |
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| `\. \* \\` | Escape special character used by regex |
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| `\t` | Tab |
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| `\n` | Newline |
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| `\r` | Carriage return |
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### Groups
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| Pattern | Description |
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| --------- | -------------------------------------------------------- |
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| `(abc)` | Capture group |
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| `(a|b)` | Match `a` or `b` |
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| `(?:abc)` | Match `abc`, but don't capture |
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| `\1` | Substituted with text matched of the 1st capturing group |
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### Quantifiers
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| Pattern | Description |
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| -------- | --------------------- |
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| `a*` | Match 0 or more |
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| `a+` | Match 1 or more |
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| `a?` | Match 0 or 1 |
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| `a{5}` | Match exactly 5 |
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| `a{,3}` | Match up to 3 |
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| `a{3,}` | Match 3 or more |
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| `a{1,3}` | Match between 1 and 3 |
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### Lookahead & Lookbehind
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| Pattern | Description |
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| --- | --- |
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| `a(?=b)` | Match `a` in `baby` but not in `bay` |
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| `a(?!b)` | Match `a` in `Stan` but not in `Stab` |
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| --- | --- |
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| `(?<=a)b` | Match `b` in `crabs` but not in `cribs` |
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| `(?<!a)b` | Match `b` in `fib` but not in `fab` |
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