Extract Emails from QString using Regex

AmrCoder

I am trying to extract some emails from text in QString have many words some of it emails so I think to use regex to do that I use this code

int main() {

  string s;
  while (getline(cin, s)) {
  QRegExp rx("^[0-9a-zA-Z]+([0-9a-zA-Z]*[-._+])*[0-9a-zA-Z]+@[0-9a-zA-Z]+([-.][0-9a-zA-Z]+)*([0-9a-zA-Z]*[.])[a-zA-Z]{2,6}$"); // create the regular expression
  rx.indexIn(QString::fromStdString(s));
  QStringList l = rx.capturedTexts();
  cout << "size = " << l.size() << endl;
  for (QString i : l) {
  if (!i.isEmpty()) {
  qDebug() << i;
  }
  }

  //check if it work on only one word using QRegular Expression
  /*QRegularExpression reg("^[0-9a-zA-Z]+([0-9a-zA-Z]*[-._+])*[0-9a-zA-Z]+@[0-9a-zA-Z]+([-.][0-9a-zA-Z]+)*([0-9a-zA-Z]*[.])[a-zA-Z]{2,6}$");
  if (reg.match(QString::fromStdString(s)).hasMatch()) {
  puts("YES valid");
  }
  else {
  puts("Not Email");
  }*/
  }
}

but it have some problems First I use the commented code to check if it work on just an email address alone like those to check that the regex I use works on emails

dsads@gmail.com
habobo887@gmail.com

and it works no problem the problem is when I try to add a full string and use the uncommented code to extract the emails from it like this

hello iam here this a full article that may contains emails like this hopeitworks@gmail.com ...etc

it not work it output nothing the size of the QstringList is 4 but all strings in it is empty
if I enter only the email it output

size = 4
"hopeitworks@gmail.com"
"mail." // !! this wrong output

so what I should do to fix this and only get in the QStringList only the emails in the text I don't know where is the problem if it's in the regex I use or what
Thanks in advance

Chris Hennes

First, I suspect your regex is not what you really want to capture, and second, I think you are misunderstanding what QRegExp::capturedTexts() returns (though I could be wrong on one or both counts, of course!).

First, "^[0-9a-zA-Z]+" matches the first word of the line, whatever that is. I'm not sure why in a general text string you would want to do that. In particular, I don't really see why you would want the caret, which makes that string only match the first word of the string. I think you probably want to drop that entire term.

After that I think you are probably just overcomplicating matters. To get a Regex that literally matches 100% of valid emails is indeed complex (you can find the answer via Google, you are looking for a regex that matches RFC 5322 Section 3.4.1), but one that will get you almost all practical email addresses is "[0-9a-zA-Z+-_.]+@[0-9a-zA-Z-]+.[0-9a-zA-Z-.]+". In that case capturedTexts() should just give you a list of email addresses, since there are no sub-expressions to deal with.