Regular Expression notes

gistfile1.txt

 			-> matches any character
+ 			-> means match 1 or more times
*			-> means match 0 or more times 
{5} 		-> means match {n} times
{3,5}		-> means 3 or up to 5 times
^ 			-> means NOT
[] 			-> character set
\ 			-> escape a special meaning
\s 			-> represents a space ( matches space, tab or line break )
\w 			-> represents a word character ( lower or uppercase letter or a number )
?			-> character before question mark is optional
()			-> capture group ( what is inside capture group can be used via $1, $2, $3 etc variables on page )
(ht|f)tps? 	-> match a url of https, http, ftp or ftps
|			-> OR
(:?ht|f)tps?-> match a url of https, http, ftp or ftps but don't make a capture group
i 			-> flag after /expression/i that means that the case of letters is not important