8 basics of regular expression that can make you expert

Well, regular expressions have been something that I was scared of when I started coding as a serious stuff. The string literals puzzled me like anything. preg_match, preg_grep, preg_split, preg_replace etc have been something I always wanted to avoid. But thanks to phpbuilder and php that I can now handle them with some ease. And this is for you guys who find regular expressions tacky.


VERY BASICS:
1. "^tech" : Searches a string that starts with tech.
2. "logy$" : Searches for strings that ends up in logy.
3. "a*b" : Looks for a string that has either zero or more a’s but exactly one b following a. (eg. b, ab, aab, aaab, aaaaaaaaaaaaaaaaab etc.).
4. "a+b" : Same as a*b but only difference is that atleast one a should be there in the string unlike a*b which can overlook a. (eg. ab, aab,aaaaaaaaab etc).

5. "a?b" : In this case string might have either zero or a single a (eg. ab or b) only these two possibilities are there.

QUANTIFYING THE CHARACTERS:
To quantify the characters into certain sets and utilize them we can use paranthesis().
6. "(abc)+def" : Matches a string which consists of pattern having abc either one or n times followed by def at the end.

LOGICAL OPERATORS [OR(|) & AND(.)]:
7. "(a|b)*c" : A string of a and b that ends in a c.

To specify range of characters. For instance to match that in a password small-case character, you can specify the set as [a-z] or [A-Z] or [0-9].
8. "([a-z])|([A-Z])" : Searches for a pattern having either small-case or capital letters.


originaly posted by: Ratno's Blog