Following are the important notations of regular expression:
[ ] matches only one character position with provided in between - it is used to match limit range of char or number provided in [ ] e.g [0-9] ^ it is used to negate the expression if it is inside of [ ] e.g [^fF] ^ outside [ ] means to match only at the begenning of target string $ user to match at the end of target string . used to match any char in this position escape character ? matches preceding char occurance 0 or 1 times only * matches preceding char occurance 0 or more times only + matches preceding char occurance 1 or more times { } matches preceding char occurance n times exactly e.g [char]{n} {n,m}