Question

I am creating a Linux terminal program using C.

I am trying to make a two digit code address a array location.
I don’t want to have to hit enter after every two digit input, I want the input to just be sent to my buffer variable through scanf directly after to characters are entered.

I do not have a code sample, as i have no idea how to approach this.

Thanks for any help!

Answer 1

You’ve got two options, which solve the same problem in nearly the same way. The first is to use stdbuf when you run your program; the invocation is:

 stdbuf -i0 ./a.out

Using that prevents stdin from being line-buffered, and will let you use fread() or similar commands to retrieve input as it happens.

The other is to put the terminal in raw mode. It’s well-described here. But the downside is that control characters are no longer dealt with. In your program, you

#include <termios.h> 

main(){
    struct termios trm;

    tcgetattr(STDIN_FILENO, &trm); /* get the current settings */
    trm.c_cc[VMIN] = 1;     /* return after 1 byte read; you might make this a 2*/
    trm.c_cc[VTIME] = 0;    /* block forever until 1 byte is read */
    tcsetattr(STDIN_FILENO, TCSANOW, &trm); 
}