Question: I want to match a string given in an input field. 

```
A sample data could be "hello" -> returns true 
or "\"" -> returns true 
or "this is a string" -> returns true 
but """ should not be recognized as a string and should return false when checked by the regexp.

```

I am initializing a boost regex parser as follow:

```
    std::string myString = "\"\"\"";
    boost::smatch match;
    boost::regex regExpString3("[\"']((:?[^\"']|\\\")+?)[\"']");
    bool statusString3 = boost::regex_match(myString, match, regExpString3);

```

The regex\_match should not match but unfortunately it does match ... 

I checked on several online reggex tester: my regular expression did not match (as expected).

Any idea if this could be a bug of boost or am I doing something wrong ?

[Debuggex Demo: Click me to verify ("[\"']((:?[^\"']|\\")+?)[\"']"](https://www.debuggex.com/r/x7PPH1YzPf1uwUgo)

Thanks

Answer: 
Try the following expression:

```
([\\"'])(?:[^\\"]|\\\\")+\\1

```

[Regex101 Demo](http://regex101.com/r/dQ0zF1)
A regular expression is overkill for this simple check. Just check the string for an opening quotation mark, then search for the next quotation mark that isn't precede by a backslash. If that second quotation mark isn't at the end, the string isn't in the correct format.