Dart Starting to In-depth Roadmap:

Dart Language — 45 minutes Quick Start (PART 1)

Dart Language — 45 minutes Quick Start (part 2)

Dart asynchronous programming in detail

Dart language asynchronous Stream details

Dart language standard flow and file manipulation

Dart Network programming

Dart crawler development experience

Dart full stack server development

Dart FFI calls C hybrid programming

Dart and Lua invocation in LuaDardo

Pay attention to me, not bad!

Standard input output stream

• stdin
• stdout
• stderr

// Import the IO package
import 'dart:io';

void main() {
  // Write a string to the standard output stream
  stdout.write('root\$:');
  // Reads a string from the standard input stream
  var input = stdin.readLineSync();
  // Write data with newline character
  stdout.writeln("input data:$input");
  // Write data to the standard error stream
  stderr.writeln("has not error");
}
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In addition to readLineSync, stdin can use readByteSync to read a single byte.

File operations

Write files

A simple operation mode, no need to manually close the file, the file will be automatically closed after the completion of writing

import 'dart:io';

void main() async{
  // Create a file
  File file = new File('test.txt');
  String content = 'The easiest way to write text to a file is to create a File';

  try {
    // Writes a string to the file
    await file.writeAsString(content);
    print('Data written.');
  } catch (e) {
    print(e); }}Copy the code

WriteAsString prototype

  Future<File> writeAsString(String contents,
      {FileMode mode: FileMode.write,
      Encoding encoding: utf8,
      bool flush: false})
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• modeFile mode, which Rimmer thinks is write mode
• encodingCharacter encoding. The default is UTF-8
• flushWhether to flush the cache immediately. Default is false

Constant for FileMode FileMode

In addition to the writeAsString method, you can use writeAsBytes to write a list of bytes. Note that both of these methods are executed asynchronously, returning a Future, and you can also use synchronous methods to perform writes if necessary

• writeAsStringSync
• writeAsBytesSync

For more flexible control, you can use the following method to operate the file, but you need to manually close the file

import 'dart:io';

void main() async{
  // Create a file
  File file = new File('test.txt');
  // Set file mode to append
  IOSink isk = file.openWrite(mode: FileMode.append);

  // Write multiple times
  isk.write('A woman is like a tea bag');
  isk.writeln('you never know how strong it is until it\'s in hot water.');
  isk.writeln('-Eleanor Roosevelt');
  await isk.close();
  print('Done! ');
}
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Read the file

Easy way

• readAsBytes
• readAsBytesSync
• readAsString
• readAsStringSync
• readAsLines
• readAsLinesSync

void main() async{
  File file = new File('test.txt');
  try{
    String content = await file.readAsString();
    print(content);
  }catch(e){
    print(e); }}Copy the code

Another, lower level approach

import 'dart:io';
import 'dart:convert';

void main() async{
  try {
    // LineSplitter is a line break encapsulated in the Dart language, where text is split by line
    Stream lines = new File('test.txt').openRead()
    	.transform(utf8.decoder).transform(const LineSplitter());

    await for (var line in lines) {
      print(line); }}catch(_) {}}Copy the code

Other operations on files

import 'dart:io';

void main() async{
  File file = new File('test.txt');

  // Check whether the file exists
  if(await file.exists()){
    print("File exists");
  }else{
    print("File does not exist");
  }

  // Copy the file
  await file.copy("test-1.txt");

  // Change the file name. Can be used to move files when different paths are passed in
  await file.rename("test-2.txt");
  
  // Get the file size
  print(await file.length());
}
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In turn, these methods have synchronized versions with the Sync suffix, such as copySync, renameSync, and so on.

To get more information about a File, you can also use FileSystemEntity, a superclass of multiple classes such as File

import 'dart:io';

void main() async{
  String path = 'test.txt';

  // Check whether the path is a folder
  if (!await FileSystemEntity.isDirectory(path)) {
    print('$path is not a directory');
  } 

 Directory dir = Directory(r'D:\workspace\dart_space\Tutorial');
 // Whether the directory exists
 if(await dir.exists()){
   // Get FileSystemEntity objects from the list method of the directory
   Stream<FileSystemEntity> fse = await dir.list();
   await for (FileSystemEntity entity in fse) {
     if(entity is File){
       print("entity is file");
     }

     // Prints the file information
     print(await entity.stat());
     / / delete
     awaitentity.delete(); }}else{
   // Create one if it does not exist. When recursive is true, create all nonexistent directories on the path
   await dir.create(recursive: true); }}Copy the code

Note that delete contains an optional parameter, prototype Future

delete({bool recursive: false}). Recursive defaults to false. When deleting a directory, the directory must be empty before deleting it. When recursive is set to true, all subdirectories and files under the directory are deleted.

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