testcase.c

#include <inttypes.h>
#include <stdio.h>
#include <sys/statvfs.h>

int getDiskSpace(const char *path, uint64_t *free, uint64_t *total) {
    struct statvfs stat;

    if (statvfs(path, &stat) < 0) {
        return -1;
    }

    *total = stat.f_frsize * stat.f_blocks;
    *free = stat.f_frsize * stat.f_bfree;
    return 0;
}

int main(int argc, char **argv) {
    uint64_t free, total;

    if(getDiskSpace(argv[1], &free, &total) < 0) {
        printf("Error");
        return 1;
    } else {
        printf("total: %" PRIu64 "\n", total);
        printf("free: %" PRIu64 "\n", free);
        return 0;
    }
}