#include <iostream>  // so I can do reasonable i/o

#include <sys/types.h>  // open at least
#include <sys/stat.h>   // open
#include <fcntl.h>      // open
#include <unistd.h>     // read

#include <string.h>  // strcmp
#include <stdio.h>   // perror

#include <iomanip>

using namespace std;

void Usage(char * progname) {
      cerr << "\tUsage " << progname << " sides" << endl;
      cerr << "\t    sides must be positive " << endl;
}

int main( int argc, char * argv[]) {

   int sides = 6;
   srand(time(nullptr));

   if (argc != 2) {
       Usage(argv[0]); 
   } else {
       sides = atoi(argv[1]);
       if (sides < 1) {
           Usage(argv[0]);
           sides = 6;
       }
   } 

   int theFD, 
       openFlags {O_CREAT | O_RDWR | O_TRUNC};
   mode_t filePerms{ filePerms = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH};

   theFD = open("diceFile", openFlags, filePerms);

   if (theFD == -1){
       perror("Could not open the output file ");
       return 1;
   }

   int tmp{0};
   int count;
   for(int i = 0; i < sides; ++i) {
      write(theFD, &tmp, sizeof(int));
   }

   for(int i = 0; i < 1'000; ++i) {
         tmp = static_cast<int>(rand() % sides);
         lseek(theFD, tmp*sizeof(int), SEEK_SET);
         read(theFD, &count, sizeof(int));
         ++count;
         lseek(theFD, -1*sizeof(int), SEEK_CUR);
         write(theFD, &count, sizeof(int));
         cout << tmp  << "   " << count << endl;
   }

   cout << endl << endl;

   lseek(theFD, 0, SEEK_SET);

   for(int i = 0; i < sides ; ++i) {
       read(theFD,  &count, sizeof(int));  
       cout  << setw(10) << i << setw(20) << count << endl;
   }


   return 0;
}