/* <b>The code must be recursive, since this is a directory traversal</b> */

void find_txt_files(char *directory, JRB lines)
{
  DIR *d;             /* <b>Directory pointer</b> */
  struct dirent *de;  /* <b>Directory entry</b> */
  char *path;         /* <b>Path name that must be constructed for each file</b> */
  Dllist dirs, tmp;   /* <b>List of directories to traverse</b> */
  struct stat buf;    /* <b>Stat buffer to check for directories</b> */
  IS is;              /* <b>Inputstruct to read the first line of a file</b> */

  /* <b>First preallocate space for the constructed pathname</b> */

  path = (char *) malloc(sizeof(char)*(strlen(directory)+258));
  if (path == NULL) { perror("malloc"); exit(1); }

  /* <b>Open the directory, and create the list of subdirectories</b> */

  d = opendir(directory);
  if (d == NULL) { perror(directory); exit(1); }
  dirs = new_dllist();
  
  /* <b>Traverse the directory</b> */

  for (de = readdir(d); de != NULL; de = readdir(d)) {

    /* <b>Construct the file name, then test to see if it is a 
       subdirectory that must be traversed -- remember to 
       ignore . and ..</b> */

    sprintf(path, "%s/%s", directory, de->d_name);
    if (lstat(path, &buf) == 0 && strcmp(de->d_name, ".") != 0 
         && strcmp(de->d_name, "..") != 0) {
      if (S_ISDIR(buf.st_mode)) {
        dll_append(dirs, new_jval_s(strdup(path)));
      }
    }

    /* <b>If the file ends with .txt, then read its first line and put
        it into the red black tree.</b> */

    if (strlen(path) >= 4 && strcmp(".txt", path+(strlen(path)-4)) == 0) {
      is = new_inputstruct(path);
      if (is != NULL) {
        if (get_line(is) >= 0) {
          jrb_insert_str(lines, strdup(is->text1), new_jval_v(NULL));
        }
        jettison_inputstruct(is);
      }
    }
  }

  /* <b>Close the directory and traverse subdirectories</b> */

  closedir(d);
  dll_traverse(tmp, dirs) find_txt_files(tmp->val.s, lines);

  /* <b>Free up memory -- the directory names, the list, path</b> */

  dll_traverse(tmp, dirs) free(tmp->val.s);
  free_dllist(dirs);
  free(path);

  return;
}
    
/* <b>The main routine -- create the red black tree, make the first
   recursive call to find_txt_files, traverse the tree and print out
   the first lines</b> */

main()
{
  JRB lines, tmp;

  lines = make_jrb();
 
  find_txt_files(".", lines);
  
  jrb_traverse(tmp, lines) printf("%s", tmp->key.s);
}


<h3>Question 2: Grading</h3>