C programming - Initialization makes integer from pointer without a cast

Question

Having trouble with some command line argurments, basically just trying to make a rectangle using command line argrumnents. Here's what I've got

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

int main(int argc, char *argv[]){

    int x;
    int y;
    int i;
    int j;

    x = atoi(argv[1]);
    y = atoi(argv[2]);

    fprintf(stderr, "Height & Width Needed\n", argv[0]);

    return 1;

    for(i = 0; i < x; i++)
        for(j = 0; j < y; j++)
            printf("*");
        printf("\n");

    return 0;
}

I know this is amateur hour but I'm just starting out. Added stderr for argv[0] statement, included atio, every time compile I just get my usage statement. I tried adding curly braces on my outer loop only, and then on the outer and inner loop, still just getting my stderr every time I run with commands.

int x = argv[1]; --> x = atoi(argv[1]); (#include <stdlib.h>) — BLUEPIXY
– BLUEPIXY, Commented Jul 2, 2017 at 2:40
Command line arguments are strings. They must be converted to ints, if an int is what's desired. atoi is one way. Other options: strtol and sscanf. — user3386109
– user3386109, Commented Jul 2, 2017 at 2:43
for(i = 0; i <= x; i++) maybe --> for(i = 0; i < x; i++){ ... } — BLUEPIXY
– BLUEPIXY, Commented Jul 2, 2017 at 2:43
Thanks @BLUEPIXY, I can't believe I forgot atoi.. so I want to be able to do this without using scanf, when I put that in I'm getting "redeclaration of 'x' with no linkage.. — Kaz
– Kaz, Commented Jul 2, 2017 at 3:06

Stargateur · Accepted Answer · 2017-07-02 05:09:41Z

1

C is not like Python, you must put bracket to create block. There is no if structure around your return 1; so it will be always executed.

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

int main(int argc, char *argv[])
{
    if (argc != 3) {
        fprintf(stderr, "Usage: %s height width\n", argc > 0 ? argv[0] : "");
        return 1;
    }
    int x = atoi(argv[1]);
    int y = atoi(argv[2]);

    for (int i = 0; i < x; i++) {
        for (int j = 0; j < y; j++) {
            printf("*");
        }
        printf("\n");
    }
}

Note: atoi() don't detect error, use strtol() instead.

edited Jul 2, 2017 at 5:09

answered Jul 2, 2017 at 4:32

Stargateur

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2 Comments

Kaz Over a year ago

@Stargatuer, thanks for the help, I added this but It still doesn't seem to work. It just does nothing. Added the argc != 3 portion as well with an stderr but it still returns nothing when I (example) ./rec 3 9.....nothing, ugh I know it's something small I'm missing

Kaz Over a year ago

sorry about that. Still confused a bit on how to properly comment. I do appreciate the help.

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