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Clarify how character classes need to be specified and explain how they can be combined with other selectors in character groups.

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Signed-off-by: DL6ER <dl6er@dl6er.de>
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DL6ER
2025-03-10 19:30:26 +01:00
parent 444c2c1ba0
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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 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 `[[:digit:]]` | `[0-9]` | No | digits
`[:lower:]` | `[a-z]` | No | matched lowercase letters(FTL matches case-insensitive by default) `[[:lower:]]` | `[a-z]` | No | lowercase letters*
`[:upper:]` | `[A-Z]` | No | matched uppercase letters(FTL matches case-insensitive by default) `[[:upper:]]` | `[A-Z]` | No | uppercase letters*
`[:alpha:]` | `[A-Za-z]` | No | matches alphabetic characters `[[:alpha:]]` | `[A-Za-z]` | No | alphabetic characters*
`[:alnum:]` | `[A-Za-z0-9]` | No | matches alphabetic characters and digits `[[:alnum:]]` | `[A-Za-z0-9]` | No | alphabetic characters* and digits
`[:blank:]` | `[ \t]` | Yes | blank characters `[[:blank:]]` | `[ \t]` | Yes | blank characters
`[:cntrl:]` | N/A | Yes | control characters `[[:cntrl:]]` | N/A | Yes | control characters
`[:graph:]` | N/A | Yes | all printable characters except space `[[:graph:]]` | N/A | Yes | all printable characters except space
`[:print:]` | N/A | Yes | printable characters including space `[[:print:]]` | N/A | Yes | printable characters including space
`[:punct:]` | N/A | Yes | printable characters not space or alphanumeric `[[:punct:]]` | N/A | Yes | printable characters not space or alphanumeric
`[:space:]` | `[ \f\n\r\t\v]` | Yes | white-space characters `[[:space:]]` | `[ \f\n\r\t\v]` | Yes | white-space characters
`[:xdigit:]` | `[0-9a-fA-F]` | Yes | hexadecimal digits `[[: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 ia allowed to mix character classes with classical character groups. For example, `[a-z0-9]` is identical to `[a-z[:digit:]]`.
# Advanced examples # Advanced examples