Getting the link from a google spreadsheet with a richtext link

GoogleSpreadsheetGetLink.gs

// Returns the link of the richtext link in the given cell. If there
// is no link, returns an empty string.
// If there is a link, removes an eventual "mailto:" in front of it.
// To use it:
//
//   =getCellEmail(C2)
function getCellEmail(address) {
  var sheet = SpreadsheetApp.getActiveSheet();
  var formula = SpreadsheetApp.getActiveRange().getFormula();
  var args = formula.match(/=\w+\((.*)\)/i);
  try {
    var range = sheet.getRange(args[1]);
  }
  catch(e) {
    throw new Error(args + ' is not a valid range' + formula);
  }
  var url = range.getRichTextValue().getLinkUrl()

  if (!url) 
    return "";

  var email = url.match(/^mailto:(.*)/);
  if (email.length > 1)
    return email[1];

  return url;
}