grab raw keyboard input from event device node

#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 ("nexiting...(%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;
 
  //Setup check
  if (argv[1] == NULL){
      printf("Please specify (on the command line) the path to the dev event interface device\n");
      exit (0);
    }
 
  if ((getuid ()) != 0)
    printf ("You are not root! This may not work...\n");
 
  if (argc > 1)
    device = argv[1];
 
  //Open Device
  if ((fd = open (device, O_RDONLY)) == -1)
    printf ("%s is not a vaild device.\n", device);
 
  //Print Device Name
  ioctl (fd, EVIOCGNAME (sizeof (name)), name);
  printf ("Reading From : %s (%s)\n", device, name);
 
  while (1){
      if ((rd = read (fd, ev, size * 64)) < size)
          perror_exit ("read()\n");      
 
      value = ev[0].value;
 
      if (value != ' ' && ev[1].value == 1 && ev[1].type == 1){ // Only read the key press event
       printf ("Code[%d]\n", (ev[1].code));
      }
  }
 
  return 0;
}

yantai:/home/shell.albert # ./a.out  /dev/input/event0

Reading From : /dev/input/event0 (AT Translated Set 2 keyboard)
Code[30]
aCode[48]
bCode[46]
cdCode[28]

Code[18]
eCode[33]
fCode[34]
gCode[35]
hCode[23]
iCode[36]
jCode[37]
kCode[38]
lCode[50]
mCode[49]
nCode[24]
oCode[25]
pCode[16]
qCode[19]
rCode[31]
sCode[20]
tCode[22]
uCode[47]
vCode[17]
wCode[44]
zCode[45]
xCode[21]
yCode[44]
zCode[29]
Code[46]
^C

yantai:/home/shell.albert #

by zhangshaoyan at May 20,2015.

We get the codes are same as defined in linux/input.h.