Calculate sum of files sizes, ingoring symbolic links

files_size.c

#define _XOPEN_SOURCE 500
#include <ftw.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static uint64_t total_size = 0;
static uint64_t file_count = 0;

static int calc_size(const char *fpath, const struct stat *sb, int tflag, struct FTW *ftwbuf) {
    // We are only interested in regular files (ignore directories, symlinks, etc.)
    if (tflag == FTW_F) {
        total_size += sb->st_size;
        file_count++;
    }
    return 0;
}

int main(int argc, char **argv) {
    if (argc < 2) {
        printf("Usage: %s <directory>\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    // 20 concurrent file descriptors is a safe and standard limit
    if (nftw(argv[1], calc_size, 20, FTW_PHYS) == -1) {
        perror("nftw");
        exit(EXIT_FAILURE);
    }

    printf("Total files: %llu\n", (unsigned long long)file_count);
    printf("Total real size: %llu = %1.2e bytes\n", (unsigned long long)total_size, (double)total_size);

    exit(EXIT_SUCCESS);
}