linux - Get Keyboard Interrupt in C

Question

Program:

#include<stdio.h>
void main()
{
    int time=1800;
    while(1){
        system("clear");
        time-=1;
        printf("%d
",time);
        sleep(1);
    if(time==0)
        pause();
    }
}

The above program stops when the time reaches 0. My requirement is during the runtime of the program, If I press any key like spacebar or any other key, the program gets paused and once again I press the key, the program gets resumed. So for doing this, before execution of while condition, we submit the signal handler for keyboard interrupt. In C how to do this.

What is the function used to get keyboard interrupt. I dont want to get input from the user, I want to handle the interrupt generated by the user through keyboard.

Thanks in Advance..,

Answer 1

You need conio.h for your requirement.It defines kbhit() and getch() both wait for input from keyboard.

Whenever kbhit() is called, it checks the keyboard buffer and returns a nonzero value if the buffer has any keypress otherwise 0 is returned.

The conio.h is used by MSDOS compilers and is not the part of standard C libraries (ISO). It is also not defined in POSIX.

#include<stdio.h>
#include<conio.h>

int main()
{
   while(1)
   {
       while(!kbhit())
       {
          //works continuously until interrupted by keyboard input.
          printf("M Tired. Break Me
");
       }
       getch();
   }
   return 0;
}

For linux you may use the following snippet to implement kbhit() by using fnctl() from fnctl.h for signal handling:

  #include <termios.h>
    #include <unistd.h>
    #include <fcntl.h>


        int kbhit(void)
        {
          struct termios oldt, newt;
          int ch;
          int oldf;

          tcgetattr(STDIN_FILENO, &oldt);
          newt = oldt;
          newt.c_lflag &= ~(ICANON | ECHO);
          tcsetattr(STDIN_FILENO, TCSANOW, &newt);
          oldf = fcntl(STDIN_FILENO, F_GETFL, 0);
          fcntl(STDIN_FILENO, F_SETFL, oldf | O_NONBLOCK);

          ch = getchar();

          tcsetattr(STDIN_FILENO, TCSANOW, &oldt);
          fcntl(STDIN_FILENO, F_SETFL, oldf);

          if(ch != EOF)
          {
            ungetc(ch, stdin);
            return 1;
          }

          return 0;
        }