List directories recursively in C

listdir_tree.c

#include <dirent.h>
#include <stdio.h>
#include <string.h>

#define CURRENT_DIR "."
#define PARENT_DIR ".."
#define MAX_PATH 1024

void listdir(char *dirname, int level);
void printn(char *s, int n);

int main(void) {
  listdir(CURRENT_DIR, 0);

  return 0;
}

void listdir(char *dirname, const int level) {
  DIR *directory;
  if ((directory = opendir(dirname)) == NULL) {
    fprintf(stderr, "listdir: error opening %s\n", dirname);
    return;
  }

  printn("|  ", level);
  if (level > 0)
    printf("|- ");
  puts(dirname);

  const struct dirent *entry;
  while ((entry = readdir(directory)) != NULL) {
    if (strcmp(entry->d_name, CURRENT_DIR) == 0 ||
        strcmp(entry->d_name, PARENT_DIR) == 0)
      continue;

    if (entry->d_type == DT_DIR) {
      if (strlen(dirname) + strlen(entry->d_name) + 2 > MAX_PATH) {
        fprintf(stderr, "listdir: path name too long\n");
        return;
      }

      char path[MAX_PATH];

      snprintf(path, MAX_PATH, "%s/%s", dirname, entry->d_name);
      listdir(path, level + 1);
    } else {
      printn("|  ", level);
      printf("|- %s\n", entry->d_name);
    }
  }

  if (closedir(directory) == -1)
    fprintf(stderr, "listdir: error closing %s\n", dirname);
}

void printn(char *s, const int n) {
  for (int i = 0; i < n; i++)
    printf("%s", s);
}