Regular-Expression-cheatsheet.txt

. - matches any single charactors 
? - The preceding item is not optional and will be matched, at most ], once
* - The preceding item will be matched zero or more times. 
+ - the preceding item will be matched one or more times. 
{N} - The preceding item will be matched exectly N times
{N,} - the preceding item will be matched exactly N or more times. 
{N.M} - the preceding item will be mached at least N, but not more then M times. 
- represents the range if it't not first or last in a list or the endpoint point of a range in a list. 
^ - match the empty string at the beginning of line. 
$ - match the empty string at the end of a word. 
\b - match the empty string at the edge of a word. 
\B - matche the empty string provided it's not at the edge of a word.
\< - match the empty string at the beginnning of word. 
\> - match the empty string at the end of word.