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I need a regex that will match blahfooblah but not blahfoobarblah
I want it to match only foo and everything around foo, as long as it isn't followed by bar.
I tried using this: foo.*(?<!bar) which is fairly close, but it matches blahfoobarblah. The negative look behind needs to match anything and not just bar.
The specific language I'm using is Clojure which uses Java regexes under the hood.
EDIT: More specifically, I also need it to pass blahfooblahfoobarblah but not blahfoobarblahblah.
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Example: The regex "aa\n" tries to match two consecutive "a"s at the end of a line, inclusive the newline character itself. Example: "a\+" matches "a+" and not a series of one or "a"s. ^ the caret is the anchor for the start of the string, or the negation symbol.
Basically (0+1)* mathes any sequence of ones and zeroes. So, in your example (0+1)*1(0+1)* should match any sequence that has 1. It would not match 000 , but it would match 010 , 1 , 111 etc. (0+1) means 0 OR 1.
String indexOf() Method The most common (and perhaps the fastest) way to check if a string contains a substring is to use the indexOf() method. This method returns the index of the first occurrence of the substring. If the string does not contain the given substring, it returns -1.
To match any character except a list of excluded characters, put the excluded charaters between [^ and ] . The caret ^ must immediately follow the [ or else it stands for just itself. The character '. ' (period) is a metacharacter (it sometimes has a special meaning).
/(?!.*bar)(?=.*foo)^(\w+)$/ blahfooblah # pass blahfooblahbarfail # fail somethingfoo # pass shouldbarfooshouldfail # fail barfoofail # fail NODE EXPLANATION -------------------------------------------------------------------------------- (?! look ahead to see if there is not: -------------------------------------------------------------------------------- .* any character except \n (0 or more times (matching the most amount possible)) -------------------------------------------------------------------------------- bar 'bar' -------------------------------------------------------------------------------- ) end of look-ahead -------------------------------------------------------------------------------- (?= look ahead to see if there is: -------------------------------------------------------------------------------- .* any character except \n (0 or more times (matching the most amount possible)) -------------------------------------------------------------------------------- foo 'foo' -------------------------------------------------------------------------------- ) end of look-ahead -------------------------------------------------------------------------------- ^ the beginning of the string -------------------------------------------------------------------------------- ( group and capture to \1: -------------------------------------------------------------------------------- \w+ word characters (a-z, A-Z, 0-9, _) (1 or more times (matching the most amount possible)) -------------------------------------------------------------------------------- ) end of \1 -------------------------------------------------------------------------------- $ before an optional \n, and the end of the string If you only want to exclude bar when it is directly after foo, you can use
/(?!.*foobar)(?=.*foo)^(\w+)$/ You made an update to your question to make it specific.
/(?=.*foo(?!bar))^(\w+)$/ fooshouldbarpass # pass butnotfoobarfail # fail fooshouldpassevenwithfoobar # pass nofuuhere # fail (?=.*foo(?!bar)) ensures a foo is found but is not followed directly bar
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