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Merge pull request #1204 from pi-hole/tweak/regex_digit

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Improve regex documentation
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Dominik
2025-03-12 18:18:28 +01:00
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docs/regex/tutorial.md
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@@ -89,20 +89,24 @@ Example | Interpretation
In addition to character groups, there are also some special character classes available, such as
Character class | Group equivalent | Pi-hole specific | Interpretation
Character class | Equivalent | Pi-hole specific | Interpretation
--------------- | ---------------- | ---------------- | ---------------
`[:digit:]` | `[0-9]` | No | matches digits
`[:lower:]` | `[a-z]` | No | matched lowercase letters(FTL matches case-insensitive by default)
`[:upper:]` | `[A-Z]` | No | matched uppercase letters(FTL matches case-insensitive by default)
`[:alpha:]` | `[A-Za-z]` | No | matches alphabetic characters
`[:alnum:]` | `[A-Za-z0-9]` | No | matches alphabetic characters and digits
`[:blank:]` | `[ \t]` | Yes | blank characters
`[:cntrl:]` | N/A | Yes | control characters
`[:graph:]` | N/A | Yes | all printable characters except space
`[:print:]` | N/A | Yes | printable characters including space
`[:punct:]` | N/A | Yes | printable characters not space or alphanumeric
`[:space:]` | `[ \f\n\r\t\v]` | Yes | white-space characters
`[:xdigit:]` | `[0-9a-fA-F]` | Yes | hexadecimal digits
`[[:digit:]]` | `[0-9]` | No | digits
`[[:lower:]]` | `[a-z]` | No | lowercase letters*
`[[:upper:]]` | `[A-Z]` | No | uppercase letters*
`[[:alpha:]]` | `[A-Za-z]` | No | alphabetic characters*
`[[:alnum:]]` | `[A-Za-z0-9]` | No | alphabetic characters* and digits
`[[:blank:]]` | `[ \t]` | Yes | blank characters
`[[:cntrl:]]` | N/A | Yes | control characters
`[[:graph:]]` | N/A | Yes | all printable characters except space
`[[:print:]]` | N/A | Yes | printable characters including space
`[[:punct:]]` | N/A | Yes | printable characters not space or alphanumeric
`[[:space:]]` | `[ \f\n\r\t\v]` | Yes | white-space characters
`[[:xdigit:]]` | `[0-9a-fA-F]` | Yes | hexadecimal digits
*) FTL matches case-insensitive by default as case does not matter in domain names
Note that character classes are abbreviations, they need to be used in character groups, i.e., enclosed in `[]`. As such, the equivalent of `[0-9]` would be `[[:digit:]]`, *not* `[:digit:]`. It is allowed to mix character classes with classical character groups. For example, `[a-z0-9]` is identical to `[a-z[:digit:]]`.
# Advanced examples