tree.c

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

#define error(msg) printf("%s\n", msg); exit(1);

void showdir(char *, char *);

int main(int argc, char **argv) {
  char *dir;
  if (argc == 1){
    dir = get_current_dir_name();
  } else if (argc >= 2) {
    dir = argv[1];
  }

  showdir("", dir);
}


void showdir(char *prefix, char *dir_name) {
  DIR *dir_stream = opendir(dir_name);

  printf("%s %s\n", prefix, dir_name);
  struct dirent *direntp;
  char *prefix_buf = malloc(strlen(prefix) + 3);
  strcat(prefix_buf, prefix);
  strcat(prefix_buf, " |");

  while ((direntp = readdir(dir_stream)) != NULL) {
    if (strcmp(direntp->d_name, ".") == 0
        || strcmp(direntp->d_name, "..") == 0 ) {
      continue;
    }
    if (direntp->d_type == DT_DIR) {
      char *new_dir_name = malloc(strlen(dir_name) + strlen(direntp->d_name) + 2);
      strcat(new_dir_name, dir_name);
      strcat(new_dir_name, "/");
      strcat(new_dir_name, direntp->d_name);
      showdir(prefix_buf, new_dir_name);
    } else {
      printf("%s-%s\n", prefix_buf, direntp->d_name);
    }
  }
}