Regular expression grammar

The Hyades Generic Log Adapter editor allows you to use regular expressions to describe how log files should be transformed into Common Base Event records. The following tables are a guideline to regular expression usage.

General rules

Regular expression matching

Expression	Matches
`{n,m}`	at least n but not more than m times
`{n,}`	at least n times
`{n}`	exactly n times
`*`	0 or more times
`+`	1 or more times
`?`	0 or 1 times
`.`	everything except \n in a regular expression within parentheses
`^`	a null token matching the beginning of a string or line (i.e., the position right after a newline or right before the beginning of a string) in a regular expression within parentheses
`$`	a null token matching the end of a string or line (that is, the position right before a newline or right after the end of a string) in a regular expression within parentheses
`\b`	backspace inside a character class ([abcd])
`\b`	null token matching a word boundary (`\w` on one side and `\W` on the other)
`\B`	null token matching a boundary that isn't a word boundary
`\A`	only at beginning of string
`\Z`	only at end of string (or before newline at the end)
`\`	newline
`\r`	carriage return
`\t`	tab
`\f`	formfeed
`\d`	digit [0-9]
`\D`	non-digit [^0-9]
`\w`	word character [0-9a-z_A-Z]
`\W`	non-word character [^0-9a-z_A-Z]
`\s`	a whitespace character [ \t\n\r\f]
`\S`	a non-whitespace character [^ \t\n\r\f]
`\xnn`	the hexadecimal representation of character nn
`\cD`	the corresponding control character
`\nn` or `\nnn`	the octal representation of character nn unless a backreference.
`\1, \2, \3` ...	whatever the first, second, third, and so on, parenthesized group matched. This is called a backreference. If there is no corresponding group, the number is interpreted as an octal representation of a character.
`\0`	the null character. Any other backslashed character matches itself .
`*?`	0 or more times
`+?`	1 or more times
`??`	0 or 1 times
`{n}?`	exactly n times
`{n,}?`	at least n times
`{n,m}?`	at least n but not more than m times

Perl 5 extended regular expressions

Expression	Matches
`(?#text)`	An embedded comment causing text to be ignored.
`(?:regexp)`	Groups things like "()" but doesn't cause the group match to be saved.
`(?=regexp)`	A zero-width positive lookahead assertion. For example, `\w+(?=\s)` matches a word followed by whitespace, without including whitespace in the MatchResult
`(?!regexp)`	A zero-width negative lookahead assertion. For example `foo(?!bar)` matches any occurrence of `foo` that isn't followed by `bar`. This is a zero-width assertion, which means that `a(?!b)d` matches `ad` because `a` is followed by a character that is not `b` (the `d`) and `d` follows the zero-width assertion.
`(?imsx)`	One or more embedded pattern-match modifiers: `i` enables case insensitivity`m` enables multiline treatment of the input`s` enables single-line treatment of the input`x` enables extended whitespace comments