#include <stdio.h>
#include <unistd.h>

#include <signal.h>

void * handle_alarm( int n )
{
  printf( "BOOM!\n" );
  return (void *)NULL;
}

int main()
{
  int timeout = 5;
  char code[ 1000 ];

  printf( "Enter your access code (you have %d seconds): ", timeout );
  alarm( timeout );
  signal( SIGALRM, (void (*))handle_alarm );
  scanf( "%s", code );

  printf( "Thank you, you made it in time.\n" );

  return 0;
}