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Regular

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Regular expressions provide a powerful way of matching patterns, in essence anything other than a simple string literal.

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will match data - in this case file names - that have the format inputFile_NNN.txt, where N are digits. E.g. inputFile_034.txt.

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will match data - in this case file names - that have the format inputFile_YYYYMMDD.txt, where YYYYMMDD is the current date. E.g. inputFile_20130828.txt.

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will match data - in this case file names - that have the format inputFile_$fileSeq.txt. E.g. if $fileSeq="034", this will match inputFile_034.txt.

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In PhixFlow, to escape a character you must use two backslashes: \\, e.g. \\n for a new line. To match a backslash in the data you are matching, you will need four backslashes: \\\\ in your regular expression. See below for details.

Regular expression constructs, and what they match

href="#lt">line href="#ubc">block href="#ubc">category href="#lt">terminator href="#cg">capturing href="#cg">capturing a href="#cg">non
ConstructMatches
Characters
xThe character x
\\\\The backslash character
\\/The forward slash character
\\\"The double quote character
\\0nThe character with octal value 0n (0 <= n <= 7)
\\0nnThe character with octal value 0nn (0 <= n <= 7)
\\0mnnThe character with octal value 0mnn (0 <= m <= 3, 0 <= n <= 7)
\\xhhThe character with hexadecimal value 0xhh
\uhhhhThe character with hexadecimal value 0xhhhh
\\tThe tab character ('\u0009')
\\nThe newline (line feed) character ('\u000A')
\\rThe carriage-return character ('\u000D')
\\fThe form-feed character ('\u000C')
\\aThe alert (bell) character ('\u0007')
\\eThe escape character ('\u001B')
\\cxThe control character corresponding to x
Character classes
[abc]a, b, or c (simple class)
[^abc]Any character except a, b, or c (negation)
[a-zA-Z]a through z or A through Z, inclusive (range)
[a-d[m-p]]a through d, or m through p: [a-dm-p] (union)
[a-z&&[def]]d, e, or f (intersection)
[a-z&&[^bc]]a through z, except for b and c: [ad-z] (subtraction)
[a-z&&[^m-p]]a through z, and not m through p: [a-lq-z](subtraction)
Predefined character classes
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Any character (may or may not match

line terminators)

\\dA digit: [0-9]
\\DA non-digit: [^0-9]
\\sA whitespace character: [ \\t\\n\\x0B\\f\\r]
\\SA non-whitespace character: [^\\s]
\\wA word character: [a-zA-Z_0-9]
\\WA non-word character: [^\\w]
POSIX character classes (US-ASCII only)
\\p{Lower}A lower-case alphabetic character: [a-z]
\\p{Upper}An upper-case alphabetic character:[A-Z]
\\p{ASCII}All ASCII:[\\x00-\\x7F]
\\p{Alpha}An alphabetic character:[\\p{Lower}\\p{Upper}]
\\p{Digit}A decimal digit: [0-9]
\\p{Alnum}An alphanumeric character:[\\p{Alpha}\\p{Digit}]
\\p{Punct}Punctuation: One of !"#$%&'()*+,-./:;<=>?@[\]^_`{|}~
\\p{Graph}A visible character: [\\p{Alnum}\\p{Punct}]
\\p{Print}A printable character: [\\p{Graph}]
\\p{Blank}A space or a tab: [ \\t]
\\p{Cntrl}A control character: [\\x00-\\x1F\\x7F]
\\p{XDigit}A hexadecimal digit: [0-9a-fA-F]
\\p{Space}A whitespace character: [ \\t\\n\\x0B\\f\\r]
Classes for Unicode blocks and categories
\\p{InGreek}A character in the Greek block (simple block)
\\p{Lu}An uppercase letter (simple category)
\\p{Sc}A currency symbol
\\P{InGreek}Any character except one in the Greek block (negation)
[\\p{L}&&[^\\p{Lu}]] Any letter except an uppercase letter (subtraction)
Boundary matchers
^The beginning of a line
$The end of a line
\\bA word boundary
\\BA non-word boundary
\\AThe beginning of the input
\\GThe end of the previous match
\\ZThe end of the input but for the final terminator, if any
\\zThe end of the input
Greedy quantifiers
X?X, once or not at all
X*X, zero or more times
X+X, one or more times
X{n}X, exactly n times
X{n,}X, at least n times
X{n,m}X, at least n but not more than m times
Reluctant quantifiers
X??X, once or not at all
X*?X, zero or more times
X+?X, one or more times
X{n}?X, exactly n times
X{n,}?X, at least n times
X{n,m}?X, at least n but not more than m times
Possessive quantifiers
X?+X, once or not at all
X*+X, zero or more times
X++X, one or more times
X{n}+X, exactly n times
X{n,}+X, at least n times
X{n,m}+X, at least n but not more than m times
Logical operators
XYX followed by Y
X|YEither X or Y
(X)X, as a capturing group
Back references
$nWhatever the nth capturing group matched
Quotation
\\Nothing, but quotes the following character
\\QNothing, but quotes all characters until \\E
\\ENothing, but ends quoting started by \\Q
Special constructs (non-capturing)
(?:X)X, as a non-capturing group
(?idmsux-idmsux) Nothing, but turns match flags on - off
(?idmsux-idmsux:X)  X, as non-capturing group with the given flags on - off
(?=X)X, via zero-width positive lookahead
(?!X)X, via zero-width negative lookahead
(?<=X)X, via zero-width positive lookbehind
(?<!X)X, via zero-width negative lookbehind
(?>X)X, as an independent, non-capturing group

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Backslashes, escapes, and quoting

A double backslash \\ either makes an alphanumeric character a contruct (e.g. \\n means newline), or allows a special character to be quoted (e.g. use \\{ if you want to match the { character). If you escape an alphabetic character that is not a construct when escaped, you will get an error.

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Line terminators

A line terminator is a one- or two-character sequence that marks the end of a line of the input character sequence. The following are recognized as line terminators:

  • A newline (line feed) character ('\\n'),
  • A carriage-return character followed immediately by a newline character ("\\r\\n"),
  • A standalone carriage-return character ('\\r'),
  • A next-line character ('\\u0085'),
  • A line-separator character ('\\u2028'), or
  • A paragraph-separator character ('\\u2029).

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Groups and capturing

Capturing groups are numbered by counting their opening parentheses from left to right. In the expression ((A)(B(C))), for example, there are four such groups:

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Groups beginning with (? are pure, non-capturing groups that do not capture text and do not count towards the group total.