找到Web应用程序客户端的操作系统

I have a requirement where I have to find the operating system details of my web app's user. If the user is running on windows it should give "Windows 7 ... Blah blah " if Linux "Ubuntu.. blah..blah OR Fedora .. .. " if Debian "whichever" version of Debian.I have a requirement where I have to find the o