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I am new to regex expressions so sorry if this is a really noob question.
I have a regex expression... What I want to do is check if a string matches the regex expression in its entirety without the regex expression matching any subsets of the string.
For example...
If my regex expression is looking for a match of \sA\s*, it should return a match if the string it is comparing it to is " A " but if it compares to the string " A B" it should not return a match.
Any help would be appreciated? I code in C#.
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Use the test() method to check if a regular expression matches an entire string, e.g. /^hello$/. test(str) . The caret ^ and dollar sign $ match the beginning and end of the string. The test method returns true if the regex matches the entire string, and false otherwise.
To run a “whole words only” search using a regular expression, simply place the word between two word boundaries, as we did with ‹ \bcat\b ›. The first ‹ \b › requires the ‹ c › to occur at the very start of the string, or after a nonword character.
$ means "Match the end of the string" (the position after the last character in the string). Both are called anchors and ensure that the entire string is matched instead of just a substring.
You can't detect regular expressions with a regular expression, as regular expressions themselves are not a regular language. However, the easiest you probably could do is trying to compile a regex from your textbox contents and when it succeeds you know that it's a regex. If it fails, you know it's not.
You would normally use the start end end anchors ^ and $ respecitvely:
^\s*A*\s*$
Keep in mind that, if you regex engine supports multi-line, this may also capture strings that span multiple lines as long as one of those lines matches the regex(since ^ then anchors after any newline or string-start and $ before any newline or string end). If you're only running the regex against a single line, that won't be a problem.
If you want to ensure that a multi-line input is only a single line consisting of your pattern, you can use \A and \Z if supported - these mean start and end of string regardless of newlines.
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