Getting user input without pausing

This is a discussion on Getting user input without pausing within the C++ Programming forums, part of the General Programming Boards category; Is there a simple way to allow user input without having the program "wait" for it? For example, I want ...

  1. #1
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    Getting user input without pausing

    Is there a simple way to allow user input without having the program "wait" for it?

    For example, I want to write a function that counts down from 100 to 0. The only way to stop it would be if the user enters a certain phrase. I want to make sure that the count down is absolutely uninterrupted unless the exact phrase is entered.

    So, how would I have a variable ready to be changed by the user, and also a function running at "the same time" so to speak?

    thanks!

    Here's some mock code for what I can come up with so far.

    Code:
    for (int i = 100; i > 0; i--)
    { 
      cin >> password;
      if (password != 'stop')
    
        // pause for 1 second
        cout << i << "..." << endl;
    }
    So that's the basic idea of what I want, except in that example, the function will pause every time and "wait" for input right?
    Last edited by Xanderbeard; 07-10-2010 at 01:54 PM.

  2. #2
    C++まいる!Cをこわせ! Elysia's Avatar
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    One way would require threads and thread synchronization.
    There are other solutions, but none of them are easy ways.
    Last edited by Elysia; 07-10-2010 at 02:40 PM.
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  3. #3
    Frequently Quite Prolix dwks's Avatar
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    It doesn't need threads. It just needs nonblocking input functions. Unfortunately there is no such thing in standard C++, but they certainly exist in other libraries. For example, Borland C++ used to have a function called kbhit() once upon a time, which would return true if there was data waiting to be read from the console and false otherwise.

    Dev-C++ may have an implementation of kbhit() (it has getche() ...), and if not the web describes a number of ways of doing it. Here's one reference for using kbhit() without ncurses on Linux: Non-blocking user input in loop without ncurses. – c/c++ programming by examples
    If you want to do this sort of thing seriously though you could look into ncurses (or pdcurses, which I hear is roughly equivalent but runs on Windows). Be warned that it might be quite a bit of work to learn a new API like ncurses, however.

    The short answer is that it's not easy, and if you're just trying to write a program that displays "the nuke will go off in X seconds!" unless you type the password, just for fun . . . it's probably not worth the hassle.

    [edit] More details:
    http://www.gamedev.net/community/for...opic_id=538714
    [/edit]
    Last edited by dwks; 07-10-2010 at 02:43 PM.
    dwk

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