Regex

=Syntax=

Metacharacters Defined || Metacharacter Examples MChar || Definition || Pattern || Sample Matches ^	Start of a string. || ^abc || abc, abcdefg, abc123, ... $	End of a string. || abc$ || abc, endsinabc, 123abc, ... .	Any character (except \n newline) || a.c || abc, aac, acc, adc, aec, ... {...}	Explicit quantifier notation. [...]	Explicit set of characters to match. (...)	Logical grouping of part of an expression. +	1 or more of previous expression. ?	0 or 1 of previous expression; also forces minimal matching when an expression might match several strings within a search string. \	Preceding one of the above, it makes it a literal instead of a special character. Preceding a special matching character, see below.
 * Alternation.
 * 0 or more of previous expression.

bill|ted	ted, bill ab{2}c	abbc a[bB]c	abc, aBc (abc){2}	abcabc ab*c	ac, abc, abbc, abbbc, ... ab+c	abc, abbc, abbbc, ... ab?c	ac, abc a\sc	a c

=Examples= 1. To Match upto 999.999.999.999: \b\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\b OR shortened with a quantifier to: \b(?:\d{1,3}\.){3}\d{1,3}\b 2. To match exactly upto 255.255.255.255:  \b(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\b OR shortened with a quantifier to: \b(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\b
 * For IP Addresses:

1. Visa card numbers start with a 4. New cards have 16 digits. Old cards have 13: ^4[0-9]{12}(?:[0-9]{3})?$ 2. MasterCard numbers start with the numbers 51 through 55. All have 16 digits: ^5[1-5][0-9]{14}$
 * For Credit Card numbers: