regex should match only one of two types of quoted strings

Question

I need a regex that match a string that is surrounded by double quotes. It should not match a string surrounded by double quotes if this pattern is surrounded by single quotes:

"string"
" 'xyz' "
"  `"    "
"  `" `"   "
"  `" `" `"  "
'  ' "should match" '  '
'   "should not match"   '

Now I have (https://regex101.com/r/z5PayV/1)

(?:"(([^"]*`")*[^"]*|[^"]*)") 

that matches all lines. But the last line should not be matched. Any solution?

Answer 1

You have to go past single quotes to exclude them from the match

update

For C# it has to be done like this.
Just uses a simple CaptureCollection to get all
the quoted matches.

(?:'[^']*'|(?:"(([^"]*`")*[^"]*|[^"]*)")|[\S\s])+

Expanded

 (?:
      ' [^']* '

   |  
      (?:
           "
           (                             # (1 start)
                ( [^"]* `" )*                 # (2)
                [^"]* 
             |  [^"]* 
           )                             # (1 end)
           "
      )
   |  
      [\S\s] 
 )+

C# code

var str =
"The two sentences are 'He said \"Hello there\"' and \"She said 'goodbye' and 'another sentence'\"\n" +
"\"  `\"    \"\n" +
"\"  `\"    \"\n" +
"\"  `\" `\"   \"\n" +
"\"  `\" `\" `\"  \"\n" +
"'   \"   \"   '\n" +
"\"string\"\n" +
"\" 'xyz' \"\n" +
"\"  `\"    \"\n" +
"\"  `\" `\"   \"\n" +
"\"  `\" `\" `\"  \"\n" +
"'  ' \"should match\" '  '\n" +
"'   \"should not match\"   '\n";

var rx = new Regex( "(?:'[^']*'|(?:\"(([^\"]*`\")*[^\"]*|[^\"]*)\")|[\\S\\s])+" );

Match M = rx.Match( str );
if (M.Success)
{
    CaptureCollection cc = M.Groups[1].Captures;
    for (int i = 0; i < cc.Count; i++)
        Console.WriteLine("{0}", cc[i].Value);
}

Output

She said 'goodbye' and 'another sentence'
  `"
  `"
  `" `"
  `" `" `"
string
 'xyz'
  `"
  `" `"
  `" `" `"
should match

---

Excuse this, it is the way it's done in PCRE engine

'[^']*'(*SKIP)(*FAIL)|(?:"(([^"]*`")*[^"]*|[^"]*)")`

https://regex101.com/r/gMiVDU/1

   ' [^']* '
   (*SKIP) (*FAIL) 
|  
   (?:
        "
        (                             # (1 start)
             ( [^"]* `" )*                 # (2)
             [^"]* 
          |  [^"]* 
        )                             # (1 end)
        "
   )

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