count files (works on macOS and Linux)

count-files.c

#include <dirent.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifdef __APPLE__
#include <sys/syslimits.h>
#endif
#include <sys/types.h>

int count(char *path, size_t n) {
  int r = 0;
  size_t name_len;

  struct dirent *f;
  DIR *d = opendir(path);
  if (!d) {
    perror(path);
    exit(EXIT_FAILURE);
  }

  while ((f = readdir(d))) {
    if (f->d_name[0] == '.') {
      if (f->d_name[1] == '\0') continue;
      if (f->d_name[1] == '.' && f->d_name[2] == '\0') continue;
    }
    ++r;
    if (f->d_type == DT_DIR) {
      name_len = strlen(f->d_name);
      path[n] = '/';
      memcpy(&path[n + 1], f->d_name,
             name_len + 1);  // strcat(path, "/"); strcat(path, f->d_name);
      r += count(path, n + 1 + name_len);
      path[n] = '\0';
    }
  }

  closedir(d);
  return r;
}

int main(int argc, char **argv) {
  char path[PATH_MAX + 1];
  int c = 0;

  if (!argv[1]) {
    fprintf(stderr, "usage: %s path\n", argv[0]);
    return EXIT_FAILURE;
  }

  for (++argv; *argv; ++argv) {
    strcpy(path, *argv);
    c += count(path, strlen(path)) + 1;  // include top itself
  }
  printf("%d\n", c);
  return EXIT_SUCCESS;
}