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getch() implementation in C

Discussion in 'C' started by ahamed101, Oct 3, 2008.

  1. ahamed101

    ahamed101 New Member

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    Hi Everyone,

    I know conio.h is not available in Unix. I want to use getch(). Using curses.h needs causes the screen to clear which I don't want.

    I found a code snippet (source : internet) using termios, it works, the thing is I need to press enter/or any other key thrice...

    Code:
    #include <stdio.h>
    #include <termios.h>
    #include <unistd.h>
    
    int mygetch ( void )
    {
      int ch;
      struct termios oldt, newt;
    
      tcgetattr ( STDIN_FILENO, &oldt );
      newt = oldt;
      newt.c_lflag &= ~( ICANON | ECHO );
      tcsetattr ( STDIN_FILENO, TCSANOW, &newt );
      ch = getchar();
      tcsetattr ( STDIN_FILENO, TCSANOW, &oldt );
    
      return ch;
    }
    
    int main()
    {
    
    	printf("\n Hello World");
    	printf("\n Press any key to continue...");
    	mygetch();
    
    	return 0;
    }
    
    
    Is there something to do with the terminal settings?... I tried this in FreeBSD, its working fine... but in HP-UX, AIX its not and it is there where I want to use...

    Any suggestions on this would be of great help...

    Regards,
    Ahamed
     
  2. xpi0t0s

    xpi0t0s Mentor

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    Tested on Linux 2.6.9 and HP-UX 11.11 and there was no problem - program exited with just a single keypress. On AIX 5.2 it took four keypresses to exit.

    [...R-ing TFM...] Aha.

    ICANON: ... a read request is not satisfied until one of the following conditions is met:
    * The minimum number of characters specified by MIN are received.

    So I'd guess your problem is that MIN=3 on HPUX/AIX, and mine is that MIN=4 on AIX and 1 on the other two.
     
  3. ahamed101

    ahamed101 New Member

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    Hi xpi0t0s,
    Is there anyway we can set the MIN value?... And thanks for that info, it was new to me, wasn't aware of that...

    Regards,
    Ahamed.
     
  4. xpi0t0s

    xpi0t0s Mentor

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    It was new to me too. Part of a programmer's skillset is to be able to find information for themselves, so I recommend you try to solve this one yourself. You have a big hint, which is the info I've already found for you (basically just by Googling "icanon", although I think I first googled "aix tcgetattr").
     
  5. ahamed101

    ahamed101 New Member

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    It worked...
    newt.c_cc[VMIN] = 1;
    newt.c_cc[VTIME] = 0;

    That did it...

    Thanks a lot everyone...

    Regards,
    Ahamed.
     

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