37 lines
1.5 KiB
Plaintext
37 lines
1.5 KiB
Plaintext
[[painless-regexes]]
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=== Regexes
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Regular expression constants are directly supported. To ensure fast performance,
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this is the only mechanism for creating patterns. Regular expressions
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are always constants and compiled efficiently a single time.
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[source,painless]
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---------------------------------------------------------
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Pattern p = /[aeiou]/
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---------------------------------------------------------
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WARNING: A poorly written regular expression can significantly slow performance.
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If possible, avoid using regular expressions, particularly in frequently run
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scripts.
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[[pattern-flags]]
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==== Pattern flags
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You can define flags on patterns in Painless by adding characters after the
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trailing `/` like `/foo/i` or `/foo \w #comment/iUx`. Painless exposes all of
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the flags from Java's
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https://docs.oracle.com/javase/8/docs/api/java/util/regex/Pattern.html[
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Pattern class] using these characters:
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[cols="<,<,<",options="header",]
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|=======================================================================
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| Character | Java Constant | Example
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|`c` | CANON_EQ | `'å' ==~ /å/c` (open in hex editor to see)
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|`i` | CASE_INSENSITIVE | `'A' ==~ /a/i`
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|`l` | LITERAL | `'[a]' ==~ /[a]/l`
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|`m` | MULTILINE | `'a\nb\nc' =~ /^b$/m`
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|`s` | DOTALL (aka single line) | `'a\nb\nc' =~ /.b./s`
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|`U` | UNICODE_CHARACTER_CLASS | `'Ɛ' ==~ /\\w/U`
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|`u` | UNICODE_CASE | `'Ɛ' ==~ /ɛ/iu`
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|`x` | COMMENTS (aka extended) | `'a' ==~ /a #comment/x`
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|======================================================================= |