Directory class Null safety

A reference to a directory (or folder) on the file system.

A Directory instance is an object holding a path on which operations can be performed. The path to the directory can be absolute or relative. You can get the parent directory using the getter parent, a property inherited from FileSystemEntity.

In addition to being used as an instance to access the file system, Directory has a number of static properties, such as systemTemp, which gets the system's temporary directory, and the getter and setter current, which you can use to access or change the current directory.

Create a new Directory object with a pathname to access the specified directory on the file system from your program.

var myDir = new Directory('myDir');

Most methods in this class occur in synchronous and asynchronous pairs, for example, create and createSync. Unless you have a specific reason for using the synchronous version of a method, prefer the asynchronous version to avoid blocking your program.

Create a directory

The following code sample creates a directory using the create method. By setting the recursive parameter to true, you can create the named directory and all its necessary parent directories, if they do not already exist.

import 'dart:io';

void main() {
  // Creates dir/ and dir/subdir/.
  new Directory('dir/subdir').create(recursive: true)
    // The created directory is returned as a Future.
    .then((Directory directory) {
      print(directory.path);
  });
}

List a directory

Use the list or listSync methods to get the files and directories contained by a directory. Set recursive to true to recursively list all subdirectories. Set followLinks to true to follow symbolic links. The list method returns a Stream that provides FileSystemEntity objects. Use the listen callback function to process each object as it become available.

import 'dart:io';

void main() {
  // Get the system temp directory.
  var systemTempDir = Directory.systemTemp;

  // List directory contents, recursing into sub-directories,
  // but not following symbolic links.
  systemTempDir.list(recursive: true, followLinks: false)
    .listen((FileSystemEntity entity) {
      print(entity.path);
    });
}

The use of Futures

I/O operations can block a program for some period of time while it waits for the operation to complete. To avoid this, all methods involving I/O have an asynchronous variant which returns a Future. This future completes when the I/O operation finishes. While the I/O operation is in progress, the Dart program is not blocked, and can perform other operations.

For example, the exists method, which determines whether the directory exists, returns a boolean value using a Future. Use then to register a callback function, which is called when the value is ready.

import 'dart:io';

main() {
  final myDir = new Directory('dir');
  myDir.exists().then((isThere) {
    isThere ? print('exists') : print('non-existent');
  });
}

In addition to exists, the stat, rename, and other methods, return Futures.

Other resources

• Dart by Example provides additional task-oriented code samples that show how to use various API from the Directory class and the related File class.

• I/O for Command-Line Apps a section from A Tour of the Dart Libraries covers files and directories.

• Write Command-Line Apps, a tutorial about writing command-line apps, includes information about files and directories.