Random UUID Generator

//
//  random_uuid.c
//
//
//  Created by Jeffrey Ryan on 6/30/15.
//
//

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main(int argc, char* argv[]) {
    const int hexDigitsLen = 16;
    const char hexDigits[] = "0123456789abcdef";

    const int bufferLen = 37 * 8;
    char buffer[bufferLen + 1];
    unsigned int currentIndex = 0;

    long int numUUIDsToGenerate = -1;

    if (argc >= 2) {
        numUUIDsToGenerate = strtol(argv[1], NULL, 10);
    }
    else {
        return 1;
    }

    if (numUUIDsToGenerate <= 0) {
        return 1;
    }

    //char help[] = "01234567-9012-4567-9012-456789012345"; // REMOVE WHEN DONE

    srand(time(NULL));
    buffer[bufferLen] = '\0';

    for (int i = 0; i < numUUIDsToGenerate; i++) {
        if (currentIndex + 37 < bufferLen) {
            for (int j = 0; j < 36; j++) {
                buffer[currentIndex + j] = hexDigits[rand() % hexDigitsLen];
            }

            buffer[currentIndex +  8] = '-';
            buffer[currentIndex + 13] = '-';
            buffer[currentIndex + 18] = '-';
            buffer[currentIndex + 23] = '-';
            buffer[currentIndex + 36] = '\n';

            currentIndex += 37;
        }
        else {
            buffer[currentIndex] = '\0';
            printf("%s", buffer);
            currentIndex = 0;
            i--;
        }
    }

    if (currentIndex != 0) {
        buffer[currentIndex] = '\0';
        printf("%s", buffer);
    }

    return 0;
}