Capturing keystrokes in GNU/Linux in C without X Window

Question

If I am working in an application and I press a key from the keyboard, how can I capture that key (or string), including the source application's name, in C, under GNU/LINUX, in userland, without X Window?

Answer 1

Well, without X Window this problem is way more difficult.

For the keystroke part, you can use code similar to this one, but you have to pass the device as an argument that you are reading (keyboard, usually /dev/input/event0)

#include <linux/input.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>

int main(int argc, char **argv)
{
    int fd;
    if(argc < 2) {
        printf("usage: %s <device>\n", argv[0]);
        return 1;
    }

    fd = open(argv[1], O_RDONLY);
    struct input_event ev;

    while (1)
    {
        read(fd, &ev, sizeof(struct input_event));

        if(ev.type == 1)
            printf("key %i state %i\n", ev.code, ev.value);

        }
    }

Credits do not go to me. This code is taken from the Ventriloctrl hack to get keystrokes - http://public.callutheran.edu/~abarker/ventriloctrl-0.4.tar.gz.