Regex - how to match everything except a particular pattern

Question

How do I write a regex to match any string that doesn t meet a particular pattern  I m faced with a situation where I have to match an  A and  B  pattern

User · Answer

My answer here might solve your problem as well:

https://stackoverflow.com/a/27967674/543814

Instead of Replace, you would use Match.
Instead of group $1, you would read group $2.
Group $2 was made non-capturing there, which you would avoid.

Example:

Regex.Match("50% of 50% is 25%", "(\d+\%)|(.+?)");

The first capturing group specifies the pattern that you wish to avoid. The last capturing group captures everything else. Simply read out that group, $2.

User · Answer

pattern - re  str split  re g     will return everything except the pattern   Test here

User · Answer

B   A    then use what group 2 captures

User · Answer

You could use a look-ahead assertion      999  d 3    This example matches three digits other than 999     But if you happen not to have a regular expression implementation with this feature  see Comparison of Regular Expression Flavors   you probably have to build a regular expression with the basic features on your own   A compatible regular expression with basic syntax only would be    0-8  d d  d 0-8  d  d d 0-8    This does also match any three digits sequence that is not 999

User · Answer

The complement of a regular language is also a regular language  but to construct it you have to build the DFA for the regular language  and make any valid state change into an error  See this for an example  What the page doesn t say is that it converted   ac bd   into   a  c   b  d     ab     The conversion from a DFA back to a regular expression is not trivial  It is easier if you can use the regular expression unchanged and change the semantics in code  like suggested before

User · Answer

If you want to match a word A in a string and not to match a word B  For example  If you have a text   1  I have a two pets - dog and a cat 2  I have a pet - dog   If you want to search for lines of text that HAVE a dog for a pet and DOESN T have cat you can use this regular expression           bdog b     cat        It will find only second line   2  I have a pet - dog

User · Answer

Match against the pattern and use the host language to invert the boolean result of the match  This will be much more legible and maintainable

User · Answer

notnot  resurrecting this ancient question because it had a simple solution that wasn t mentioned   Found your question while doing some research for a regex bounty quest       I m faced with a situation where I have to match an  A and  B    pattern    The basic regex for this is frighteningly simple  B  A   You just ignore the overall matches and examine the Group 1 captures  which will contain A   An example  with all the disclaimers about parsing html in regex   A is digits  B is digits within  lt a tag  The regex   lt a    lt   a gt    d    Demo  look at Group 1 in the lower right pane    Reference   How to match pattern except in situations s1  s2  s3  How to match a pattern unless

[regex] Regex - how to match everything except a particular pattern

Examples related to regex