Table of Contents > Reference

## Regex Reference Page

Regular expressions are used in SystemTap GUI to define how the GUI interprets information that it recieves from the script file. If the user wishes to change the regular expression during runtime they may do so by selecting Edit->Modify Parsing Expression.
Basic regex (taken from http://java.sun.com/j2se/1.5.0/docs/api/ ) -

     Summary of regular-expression constructs

    Construct 	Matches

    Characters
    x 	The character x
    \\ 	The backslash character
    \0n 	The character with octal value 0n (0 <= n <= 7)
    \0nn 	The character with octal value 0nn (0 <= n <= 7)
    \0mnn 	The character with octal value 0mnn (0 <= m <= 3, 0 <= n <= 7)
    \xhh 	The character with hexadecimal value 0xhh
    \uhhhh 	The character with hexadecimal value 0xhhhh
    \t 	The tab character ('\u0009')
    \n 	The newline (line feed) character ('\u000A')
    \r 	The carriage-return character ('\u000D')
    \f 	The form-feed character ('\u000C')
    \a 	The alert (bell) character ('\u0007')
    \e 	The escape character ('\u001B')
    \cx 	The 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
    . 	Any character (may or may not match line terminators)
    \d 	A digit: [0-9]
    \D 	A non-digit: [^0-9]
    \s 	A whitespace character: [ \t\n\x0B\f\r]
    \S 	A non-whitespace character: [^\s]
    \w 	A word character: [a-zA-Z_0-9]
    \W 	A 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}\x20]
    \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]

    java.lang.Character classes (simple java character type)
    \p{javaLowerCase} 	Equivalent to java.lang.Character.isLowerCase()
    \p{javaUpperCase} 	Equivalent to java.lang.Character.isUpperCase()
    \p{javaWhitespace} 	Equivalent to java.lang.Character.isWhitespace()
    \p{javaMirrored} 	Equivalent to java.lang.Character.isMirrored()

    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
    \b 	A word boundary
    \B 	A non-word boundary
    \A 	The beginning of the input
    \G 	The end of the previous match
    \Z 	The end of the input but for the final terminator, if any
    \z 	The 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
    XY 	X followed by Y
    X|Y 	Either X or Y
    (X) 	X, as a capturing group

    Back references
    \n 	Whatever the nth capturing group matched

    Quotation
    \ 	Nothing, but quotes the following character
    \Q 	Nothing, but quotes all characters until \E
    \E 	Nothing, 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 a 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, as an independent, non-capturing group
    Match a position that is not a word boundary.

Information regarding regular expressions can be found all over the Internet. A few examples have been listed below:

- http://www.javascriptkit.com/javatutors/redev.shtml
- http://www.zytrax.com/tech/web/regex.htm