Unbiased Random Integer Generator Over a Range

rngchk.c

#include <stdio.h>                                                                      
#include <stdlib.h>                                                                     
#include <limits.h>                                                                     
#include <string.h>                                                                     
#include <time.h>                                                                       
                                                                                        
/*                                                                                      
 * generates an unsigned int between low and high, inclusive of both                    
 * taken from: https://en.cppreference.com/w/c/numeric/random/rand                      
 *                                                                                      
 * pre:   srand has been called to seed the PRNG                                        
 * in:    low and high integer values                                                   
 * out:   a random, unsigned integer between low and high, inclusive                    
 * post:  n/a                                                                           
 */                                                                                     
int get_rand( unsigned int low, unsigned int high)                                      
{                                                                                       
  int r = rand();                                                                       
  r = low + ( r / ( (RAND_MAX + 1u) / (high + 1) ) );                                   
  return r;                                                                             
}                                                                                       
                                                                                        
//checks the distribution of a billion randomly generated numbers                       
//in: low, high                                                                         
//out: a printed perecentage for each generated value from low to high                  
int main( int argc, char **args )                                                       
{                                                                                       
  if(argc != 4)                                                                         
  {                                                                                     
    printf("Usage: rngchk low high iterations\n\                                        
        where low is an integer indicating the lowest number to be generated\n\         
        high is an integer indicating the highest number to be generated\n\             
        and iterations is a long indicating the count of numbers to be generated.\n");  
    exit(1);                                                                            
  }                                                                                     
  unsigned int low = atoi( *(args+1) );                                                 
  unsigned int high = atoi( *(args+2) );                                                
  unsigned long its = atol( *(args+3) );                                                
                                                                                        
  printf("Applicable limits on this system:\n");                                        
  printf("INT_MAX: %i\n", INT_MAX);                                                     
  printf("LONG_MAX: %lu\n", LONG_MAX);                                                  
                                                                                        
  //getting a specific char in the array of strings passed in as args                   
  //char  foo = ( (*(args+3))[3] );                                                     
  //printf("This is foo: %c", foo);                                                     
                                                                                        
  int counts[high-low+1];                                                               
  memset(counts, 0, (sizeof(int)*high));                                                
  //seed the PRNG                                                                       
  srand(time(NULL));                                                                    
                                                                                        
  int x = -1;                                                                           
  for(int n = 0; n < its; n++)                                                          
  {                                                                                     
    x = get_rand(low, high);                                                            
    counts[x+low]++;                                                                    
  }                                                                                     
                                                                                        
  double p = .0;                                                                        
                                                                                        
  for (int j = 0; j < high; j++)                                                        
  {                                                                                     
    printf("Count %i: %i\n", j, counts[j]);                                             
    p = counts[j]/(its+.0);                                                             
    p *= 100;                                                                           
    printf("Percentage %i: %f\n", j, p);                                                
  }                                                                                     
                                                                                        
  return 0;                                                                             
}