在C中导航数组的指针问题

Question

I wanted to create a vector (dynamically allocated) where every element of the vector is taken from the command line starting from the 3rd parameter.

I wrote this:

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

int main(int argn, char* argc[]) {
    if (argn < 4) {
        printf("Error: invalid parameter number. \n");
        return 0;
    } 
    float min = atof(argc[1]), max = atof(argc[2]), *v, *k;
    int dim = argn-3;
    char **p;
    v = malloc(dim*sizeof(float));
    k = v;
    for (p = argc+3; p < argc+dim; p++) {
        *k = atof(*p);
        k++;
    }
    for (k = v; k < v+dim; k++) {
        printf("%3.f ",*k);
    }
    return 0;
}

The problem is that only the first parameter seems to be taken from the command line, while others not.

Example: I launch [ProgramName] 25 30 27 28 29 32

It returns me 27.0 0.0 0.0 0.0, but it should return me 27.0 28.0 .29.0 32.0

Why isn't my code working?

Sorry for eventual grammar mistakes, I'm not english.

Answer 1

You write:

int dim = argn-3;
...
for (p = argc+3; p < argc+dim; p++) {
...
}

Suppose argn==5 , then dim==2 , and the loop boils down to:

for (p = argc+3; p < argc+2; p++) {
...
}

which would never run.

On a side note, it is customary to use argc and argv as parameters of main. If you follow this, your code will be more readable to others, and others' code will be more readable to you. Besides, you forgot to print newline.