key-reader.c

#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <linux/input.h>
#include <string.h>
#include <stdio.h>

static const char *evval[3] = {
    "RELEASED",
    "PRESSED",
    "REPEATED"
};

int main(void) {
    const char *dev = "/dev/input/by-id/usb-Fujitsu_Technology_Solutions_GmbH_Fujitsu_Keyboard-event-kbd";
    struct input_event ev;
    ssize_t n;
    int fd;

    fd = open(dev, O_RDONLY);

    if (fd == -1) {
        fprintf(stderr, "Cannot open %s: %s.\n", dev, strerror(errno));
        return EXIT_FAILURE;
    }

    while (1) {
        n = read(fd, &ev, sizeof ev);

        if (n == (ssize_t) -1) {
            if (errno == EINTR) {
                continue;
            } else {
                break;
            }
        } else {
            if (n != sizeof ev) {
                errno = EIO;
                break;
            }
        }

        if (ev.type == EV_KEY && ev.value == 0) {
            if (ev.code >= 2 && ev.code <= 10) {
                printf("%d", ev.code - 1);
            } else if (ev.code == 11) {
                printf("%d", 0);
            } else if (ev.code == 28) {
                printf("\n");
            }
        }

        fflush(stdout);
    }

	fflush(stdout);
    fprintf(stderr, "%s.\n", strerror(errno));

    return EXIT_FAILURE;
}