linux keyboard return shift-key pressed state

shift_state.c

#include <sys/ioctl.h>
#include <asm/ioctls.h>
#include <stdio.h>
#include <fcntl.h>

// code by "dma" via https://forums.gentoo.org/viewtopic-p-2455159.html#2455159

int main(int argc, char *argv[]) {
 int fd;
 char shift_state;
 fd = open("/dev/console", O_RDWR);
 /*
 * From console_ioctl:
 * TIOCLINUX, subcode=6
 * argp points to a char which is set to the value of the kernel
 * variable shift_state. (Since 1.1.32.)
 */
 shift_state = 6;
 ioctl(fd, TIOCLINUX, &shift_state);
 printf("shift_state = %i\n", (int)shift_state);
 close(fd);
 return shift_state;
}

somescript.sh

#!/bin/bash

shift_state=$(sudo ~/path/to/shift_state)
if (( $shift_state )) ; then
  echo "shift-key active"
else
  echo "shift-key not active"
fi

gcc shift_state.c -o shift_state
chmod +x shift_state
sudo ./shift_state

sudo visudo

username ALL=(ALL) NOPASSWD: /path/to/shift_state