Prevent Multiple Instances

This is a discussion on Prevent Multiple Instances within the Windows Programming forums, part of the Platform Specific Boards category; Anybody know how I would go about detecting other instances of a program, to ensure that only one instance is ...

  1. #1
    Work in Progress..... Jaken Veina's Avatar
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    Prevent Multiple Instances

    Anybody know how I would go about detecting other instances of a program, to ensure that only one instance is ever running?
    Code:
    void function(void)
     {
      function();
     }

  2. #2
    Reverse Engineer maxorator's Avatar
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    The common technique is to use mutexes.

    http://msdn.microsoft.com/en-us/libr...27(VS.85).aspx

    Simply CreateMutex() when the program starts and CloseHandle() on exit (optional). If CreateMutex() fails and GetLastError() returns ERROR_ALREADY_EXISTS, then you know one instance is already running.
    Last edited by maxorator; 01-14-2009 at 02:10 PM.
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  3. #3
    train spotter
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    Did you try a search?

    8 years ago I posted code to do this with file mapping. Many others have posted similar code.
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    First codes on Win32 mutexes appeared more than 8 years ago
    Google Groups : first reference : 1995... : 14 years ago...

  5. #5
    C++まいる!Cをこわせ! Elysia's Avatar
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    Is there a really good reason for preventing multiple instances? Many users will hate it if they don't have the option to run multiple instances if they wish.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  6. #6
    Work in Progress..... Jaken Veina's Avatar
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    Well, in this case, it's a pseudo-standalone screensaver, which you can activate on command in addition to letting Windows activate it for you. It wouldn't really hurt anything, I suppose, to have multiple instances, but I like to be neat. Thanks, guys.
    Code:
    void function(void)
     {
      function();
     }

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