It is great for finding optional characters.Ĭolou?r will match both color and colour. Matches the preceding element zero or one time (it will always match if the character was not found). Used to match characters at the end of a stringĬom$ will match or telecom but not computer. Used to match characters at the beginning of a string Or you can look for a range of characters by giving two characters and separating them by a hyphen for example, net will match neta, netw and netf but not net1. You can list characters individually for instance, net will match netw, netr and netx but not netz. For example, will match any of the characters n, e, t or $ ( $ is a metacharacter, but inside a character class it matches only $). Note that metacharacters (with one exception) are not active inside classes. For example will match any character except n this is called a negated character class. Inside a class, at the beginning, the ^ means exception from the search. Matches for anything inside the square brackets. Net.rix will match both and Character class The following table describes how each of these metacharacters functions. The following single characters are not interpreted as literals but instead have special meanings: Note that regular expressions are case sensitive, so www will not match WWW or wWw. LiteralsĪny single character, except for those reserved as metacharacters, is already a regular expression itself. Regex ComponentsĪ RegEx can include literals and metacharacters. For example, you can define a RegEx that will match email addresses, PII, PHI or credit card numbers. Using this little language, you specify rules that define the strings you want to match. Regular expressions are a small but highly specialized programming language they are basically wildcards on steroids.
Data Classification for Compliance: Looking at the Nuances.
Of course, if you let your programming language evaluate something numerically rather than try to match it against a regular expression, you'll save headaches and CPU.Data Classification: What It Is, Why You Should Care and How to Perform It )$Īnd finally, we close the parentheses and anchor the regex to the end of the line with the dollar sign, just as the caret anchors to the beginning of the line. So this matches everything above 0 and below 1. This matches any number that starts with one or more 0 characters (replace + with * to match zero or more zeros, i.e.25), followed by a period, followed by a string of digits that includes at least one that is not a 0. Parentheses are used to group multiple expressions separated by or-bars.Īnd the second part: 0+\.** For purposes of evaluation of this expression, It has higher precedence than everything else, and effectively joins two regular expressions together. The pipe character is an " or-bar" in this context. The 0* at the start handles leading zeros, so 005 = 5. So our 2.0 would be matched, but 0.25 would not. This matches any integer or any floating point number above 1. The opening parenthesis is there because of the or-bar, below. The caret matches the null at the beginning of the line, so preceding your regex with a caret anchors it to the beginning of the line. Let's break the expression down into parts that are easier to digest.
The same thing can be expressed in Basic RE, but almost everything understands ERE these days. Note that this second one is an Extended RE. And while we're at it, we'll add support for leading zeros on integers (i.e. 0.25), as well as case where your pattern has a decimal part that is 0. 2.5 or 3.3̅), cases where your pattern is between 0 and 1 (i.e. If you want to match real numbers (floats) rather than integers, you need to handle the case above, along with normal decimal numbers (i.e. I don't know how MVC is relevant, but if your ID is an integer, this BRE should do: ^*$