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+?(?=abc)Ī picture is worth a thousand words. In your particular case, it can be solved by a positive look ahead. Adding the non-greedy quantifier ? makes the regex only match "whatever whatever something ".Īs Ng and pointed out, the key to solve this kind of RegEx like "matching everything up to a certain word or substring" or "matching everything after a certain word or substring" is called "lookaround" zero-length assertions. Therefore /^.*abc/ would match "whatever whatever something abc something ". The reason why this is needed is that otherwise, in the following string: whatever whatever something abc something abcīy default, regexes are greedy, meaning it will match as much as possible.
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Regex - Does not contain certain Characters.
#Regular expression not substring how to#
How to match, but not capture, part of a regex 348. How do I grep for all non-ASCII characters 253. Regular expression for a string that does not start with a sequence. But I think the reason this isnt working is dxl, because the not operator. Regex to not match if there is a substring. * match anything, ? non-greedily (match the minimum number of characters required) - I do know that there is a syntax for this in regexp: (( string to match).). Here is an example of checking if 'asd' is notin 'apples'. ( ) capture the expression inside the parentheses for access using $1, $2, etc. If word does not appear after offset, the function returns-1 Essentially with this contains function you can input a string and check if a substring exists or not. Most of the time, the regexes become easier, if not trivial. Keep it simple and stupid Do 2 matches, one for the positives, and sort out later the negatives (or the other way around). If you're looking to capture everything up to "abc": /^(.*?)abc/ My advise in such cases is not to construct overly complicated regexes whith negative lookahead assertions or such stuff. Match any characters as few as possible until a "abc" is found, Success of this subexpression's result is then determined by whether it's a. Thus, in other terms the regex /.+?(?=abc)/ means: When the regular expression engine hits a lookaround expression, it takes a substring reaching from the current position to the start (lookbehind) or end (lookahead) of the original string, and then runs Regex.IsMatch on that substring using the lookaround pattern. Only returns if it is a match or not ( assertion). This grouped construction matches itsĬontents, but does not count as characters matched ( zero width). +?X/ ~ "abcXabcXabcX" /.+?/ ~ "abcXabcXabcX"įollowing that we have (?= ), a zero widthĪssertion, a look around. +X/ ~ "abcXabcXabcX" /.+/ ~ "abcXabcXabcX" This is the un-greedy, meaning match the fewest possible to Step until the subsequent part of the regex is matched (again if any). Other conditions (if any), the engine will match the next characters by +?, instead of matching all at once and going back for Then, if there is something else in the regex it will go back in steps +, the engine will basically match everything. Work in any of the most popular ones that can be considered "complete". You didn't specify which flavor of regex you're using, but this will