getchar() returns the same value (27) for up and down arrow keys

c keyboard getchar
NoNameY0 picture NoNameY0 · Mar 9, 2013 · Viewed 13.1k times · Source

So for the up key on the keyboard, I get 27, surprisingly for the down key I also get 27. I need my program to behave differently on the up and down key, and I can't seem to figure it out. I am using Linux, and need it to work for Linux.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
int main()
{
    int c = getchar();

    if(c==27)
    {
        printf("UP");
    }

    if(c==28)
    {
        printf("DOWN");
    }

}

Answer

Ernest Friedman-Hill picture Ernest Friedman-Hill · Mar 9, 2013

The 27 implies that you're getting ANSI escape sequences for the arrows. They're going to be three-character sequences: 27, 91, and then 65, 66, 67, 68 (IIRC) for up, down, right, left. If you get a 27 from a call to getchar(), then call it twice more to get the 91 and the number that determines what arrow key was pressed.

As someone else mentioned, this is platform-specific, but you may not care.

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