in c++; strip trailing spaces and carriage return ('\r') characters (update)

In this method I need to return ("\r") if in my file if a line contains strip tailing. Is this the correct way? cause i am finding how to remove strip tailing but am not quite sure if that how i should return "\r"

std::ifstream myfile;
std::string s;
if (myfile.is_open()) {
  while (std::getline(myfile,s)) {

 
std::string& ltrim(std::string &s)
{
    auto it = std::find_if(s.begin(), s.end(),
                    [](char c) {
                        return !std::isspace<char>(c, std::locale::classic());
                    });
    s.erase(s.begin(), it);
    return s;
}
 
std::string& rtrim(std::string &s)
{
    auto it = std::find_if(s.rbegin(), s.rend(),
                    [](char c) {
                        return !std::isspace<char>(c, std::locale::classic());
                    });
    s.erase(it.base(), s.end());
    return s;
}
 
std::string& trim(std::string &s) {
    return ltrim(rtrim(s));
}