c++中將命令行中的輸出到字符流

std::string GetStdoutFromCommand(std::string cmd)
{
    std::string data;
    FILE *stream;
    const int max_buffer=256;
    char buffer[max_buffer];
    cmd.append(" 2>&1");

    stream = popen(cmd.c_str(), "r");
    if(stream)
    {
        while(!feof(stream))
        {
            if(fgets(buffer, max_buffer, stream) != NULL)
            {
                data.append(buffer);
            }
        }
        pclose(stream);
    }

    return data;
}