Capture key events from a keyboard/input device.

capkey.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <dirent.h>
#include <linux/input.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/select.h>
#include <sys/time.h>
#include <termios.h>
#include <signal.h>

void handler(int sig) {
  printf("\nEXIT(%d)\n", sig);
  exit(0);
}

void perror_exit(char *error) {
  perror(error);
  handler(9);
}

int main (int argc, char *argv[]) {
 struct input_event ev[64];
 int fd, rd, value, size = sizeof (struct input_event);
 char name[256] = "Unknown";
 char *device = NULL;

 if (argv[1] == NULL) {
  printf("Usage: %s [INPUT_DEVICE]\n", argv[0]);
  exit(0);
 }

 if ((getuid ()) == 0) printf("ROOT = TRUE\n");
 else printf("ROOT = FALSE [!]\n");

 device = argv[1];

 if ((fd = open (device, O_RDONLY)) == -1) printf("INVALID_DEVICE(%s) [!]\n", device);

 ioctl(fd, EVIOCGNAME (sizeof (name)), name);
 printf("READ(%s) [%s]\n", device, name);

 while (1) {
  if ((rd=read(fd, ev, size * 64)) < size) perror_exit("READ_ERROR");
  value = ev[0].value;
  if (value != ' ' && ev[1].value == 1 && ev[1].type == 1) {
   printf ("KEY(%d)\n", ev[1].code);
  }
 }
 return 0;
}