C randomFloatInRange executable

randomFloatsInRange.c

// DESCRIPTION
// Generates N (argv[3]) floating point numbers in range argv[1] to argv[2]. Depending on system and setup may be able to produce ~35,000N/sec.

// USAGE
// Compile for example via gcc, like this (I use an MSYS2-MinGW-64 terminal) :
//  gcc randomFloatsInRange.cpp -o randomFloatsInRange.exe
// -- and then invoke the resulting executable with these parameters (POSITIONAL, not named):
// - 1. smallest possible random number to generate. I don't know the minimum; certainly 0 is allowed.
// - 2. largest possible random number to generate. Maximum may be RAND_MAX; on my system that is: 2147483648.000000.
// - 3. how many such numbers to generate. I don't know the maximum.
// Numbers are printed to standard out, one per line. Example command that will produce 1,000 numbers as small as 0.681 and as large as 1.214:
//  randomFloatInRange 0.681 1.214 1000
// NOTE that if you do not pass all expected parameters, the program will not behave as expected, and won't even notify you of errors.


// CODE
// TO DO: option handling with helpful errors and help print.
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
// #include <unistd.h>

int main(int argc, const char *argv[]) {
		// Because I noticed calling this program more than once a second resulted in the same random result, as time seeding is only at second-resolution; seed via nanoseconds; dunno why I need a timespec ts here; re: https://stackoverflow.com/a/20201185/1397555
	struct timespec ts;
	clock_gettime(CLOCK_MONOTONIC, &ts);
	srand((time_t)ts.tv_nsec);
	float min = atof(argv[1]);
	float max = atof(argv[2]);
	char *p;
	long conv = strtol(argv[3], &p, 10);
	int countTo = conv;
	int counter = 0;
		while (counter < countTo) {
		++counter;
			// re https://stackoverflow.com/a/44105089/1397555
			// rand() gets a random number between 0 and RAND_MAX, so dividing it by RAND_MAX gets a number between 0 and 1:
		float scale = rand() / (float) RAND_MAX;				/* [0, 1.0] */
			// Then mathy math gives number in desired range:
		float rndNumber = min + scale * (max - min);		/* [min, max] */
		printf("%f\n",rndNumber);
	}
	return 0;
};