determine the OS while running

This is a discussion on determine the OS while running within the C++ Programming forums, part of the General Programming Boards category; is there any easy way for a program to determine which OS is running it? if not, is there any ...

  1. #1
    Registered User major_small's Avatar
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    determine the OS while running

    is there any easy way for a program to determine which OS is running it? if not, is there any way at all besides a user putting the information in at setup or something? what I eventually want to do is write something like this:
    Code:
    void ClearScreen()
    {
         if(OS=='W')
              system("cls");
         else if(OS=='L')
              system("clear");
         else
         {
               for(int i=500;i>1;i++)
                    std::cout<<std::endl;
         }
    }
    I already know clearing the screen should be avoided at all times, but I just wanted to create something that is a little more portable for the times where I really really need to clear the screen... (please don't post other ways to clear the screen... I really just want to know if/how you can determine which OS is running)
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  2. #2
    C++ Developer XSquared's Avatar
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    There most likely is some #defined value for Linux and for Windows, so you could probably use #if preprocessor directives.
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  3. #3
    Registered User major_small's Avatar
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    that's why i brought this up... I thought I used something like that once, but I can't seem to find the code I used it in
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  4. #4
    C++ Developer XSquared's Avatar
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    If the OSes are limited to Windows and Linux, you can just do this:
    Code:
    #ifdef __linux__
      linux stuff
    #else
      win32 stuff
    #endif
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  5. #5
    Registered User grady's Avatar
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    Which symbols are defined depends on the compiler you are using. Googling for "gcc always defines" indicates __GNUC__ for gcc. Googling for `"always defined" visual c++` indicates _WIN32 will always be defined but i'm not sure. They say its defined for win32 applications which might mean 'not console applications', but then they say always defined. You will have to experiment.

  6. #6
    and the hat of wrongness Salem's Avatar
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    > is there any easy way for a program to determine which OS is running it?
    No - the standard libraries of C and C++ are written to be as independent of the machine as possible (to make them as portable as possible).

    The answer is to call a function which is specific to your operating system, but then you run into "unresolved symbol" when you try and compile your code for something else (somewhat predictably).

    The real answer is as XSquared has said, and that is to use conditional compilation.
    To maintain some sense of sanity, its best to try and isolate anything machine specific into a few source files, like so
    Code:
    void myfoo ( void ) {
    #ifdef __linux__
      linuxfoo();
    #elif defined __win32__
      win32foo();
    #else
      #error No compatible foo
    #endif
    }
    Then all your other code calls myfoo() rather than cluttering up the code with an ever-expanding conditional complilation switch every time you want a foo().
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  7. #7
    Registered User major_small's Avatar
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    ^that's what I was planning on doing with it... as in my first example...
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