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

double TriangleArea(double a, double b, double c);

int main(int argc, const char * argv[]) {
    printf("%f\n", TriangleArea(atof(argv[1]), atof(argv[2]), atof(argv[3])));
    return 0;
}

double TriangleArea(double a, double b, double c){
    double area, p;
    p = (a + b + c) / 2;
    area = sqrt(p * (p - a) * (p - b) * (p - c));
    return area;
}

如何使用：

./tranglearea 3 4 5
6.000000