Knowledge - Transfers
Metacharacters
These need to be escaped to be matched.
\ . ^ $ * + ? { } [ ] ( ) |Escape sequences for pre-defined character classes
- \d – a digit – [0-9]
- \D – a nondigit – [^0-9]
- \w – a word character (alphanumeric including underscore) – [a-zA-Z_0-9]
- \W – a nonword character – [^a-zA-Z_0-9]
- \s – a whitespace character – [ \t\n\r\f]
- \S – a non-whitespace character – [^ \t\n\r\f]
Assertions
Assertions have zero width.
- ^ – Matches the beginning of the line
- $ – Matches the end of the line (or before a newline at the end)
- \B – Matches everywhere except between a word character and non-word character
- \b – Matches between word character and non-word character
- \A – Matches only at the beginning of a string
- \Z – Matches only at the end of a string or before a newline
- \z – Matches only at the end of a string
- \G – Matches where previous m//g left off
Minimal Matching Quantifiers
The quantifiers below match their preceding element in a non-greedy way.
- *? – zero or more times
- +? – one or more times
- ?? – zero or one time
- {n}? - n times
- {n,}? – at least n times
- {n,m}? – at least n times but not more than m times
Courtesy : http://www.somacon.com/p127.php
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