allow for parsing command line arguments for multiple coinflips at once

src/main.c

@@ -1,12 +1,46 @@
-#include <time.h>
+#include <errno.h>
+#include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
-#include <stdint.h>
+#include <time.h>
 
-int main(void) {
-    struct timespec ts;
-    clock_gettime(CLOCK_MONOTONIC, &ts);
-    srand((uint32_t)(ts.tv_nsec ^ ts.tv_sec));  // combine seconds and nanoseconds
-    printf("%s\n", (rand() & 1) ? "heads" : "tails");
-    return 0;
+int main(int argc, char** argv) {
+	// set thr seed to the number of seconds xor-ed with nanoseconds
+	{
+		struct timespec ts;
+		clock_gettime(CLOCK_MONOTONIC, &ts);
+		srand((uint32_t)(ts.tv_nsec ^ ts.tv_sec)); // combine seconds and nanoseconds
+	}
+
+	// if we have input; perform coinflips for those times
+	if (argc > 1) {
+		for (uint32_t i = 1; i < argc; ++i) {
+			int n = 0;
+			uint32_t headsc = 0;
+			uint32_t tailsc = 0;
+
+			// get the integer from the string, return 1 if an error occurred
+			errno = 0;
+			long c = strtol(argv[i], NULL, 10);
+			if (errno == EINVAL) {
+				fprintf(stderr, "syntax error for string: %s\n", argv[i]);
+				return 1;
+			}
+
+			// perform for the inputted count
+			for (long j = 0; j < c; ++j) {
+				if (n == 0) n = rand();
+				(void)((n & 1) ? headsc++ : tailsc++); // increment the correct counter
+				n >>= 1;                               // shift the random integer right by 1
+			}
+
+			// print the results
+			printf("results:\n heads: %u\n tails: %u\n", headsc, tailsc);
+		}
+		return 0;
+	}
+
+	// just print whether it's heads or tails
+	printf("%s\n", (rand() & 1) ? "heads" : "tails");
+	return 0;
 }