Question

I’m trying to build an array of strings using popen(), but every index in the array is the last string returned. I’m ultimately just trying to get a directory listing of all files into an array.

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

void main()
{
    FILE *fp;
    fp = popen("find ~/ -maxdepth 1 -type f", "r");
    if (fp == NULL) { printf("Failed to run command\n" ); exit; }

    char path[999];
    char* rawdata[999];
    int i = 0;

    while (fgets(path, sizeof(path)-1, fp) != NULL) {
        rawdata[i] = path;  // Shouldn't this assign every index
        i++;                // a different string ?
    }
    pclose(fp);

    /* Below, every index is the same string ? */
    printf("\n%s", rawdata[0]);
    printf("\n%s", rawdata[1]);
    printf("\n%s", rawdata[2]);
}

Answer 1

rawdata[i] = path;  // Shouldn't this assign every index a different string?

No. You are storing path, which is the name of an array and therefore decays into the pointer to the beginning of the array. So in fact, all of the elements of rawdata have the same value, and that is the address of the array path, which never changes.

To actually get the contents of path copied over to rawdata, you need to allocate memory for it in rawdata[i] (malloc) and then use strcpy. A shortcut for this exists in the standard library called strdup:

    ...

    while (fgets(path, sizeof(path)-1, fp) != NULL) {
        rawdata[i] = strdup(path);
        if (rawdata[i] == NULL)
            goto exit_no_mem;
        i++;
    }
    n = i;

    ...

    /* in the end */
    for (i = 0; i < n; ++i)
        free(rawdata[i]);
    return EXIT_SUCCESS;
exit_no_mem:
    fprintf(stderr, "Out of memory\n");
    return EXIT_FAILURE;

Finally, note that if you are putting a hard cap on the number of elements you are reading, make sure you don’t violate it. That is, once i reaches 999, you shouldn’t read more elements. Therefore:

    while (i < 999 && fgets(path, sizeof(path)-1, fp) != NULL)