Input and output are essential operations in any programming language, as they allow you to interact with the user, the system, or other programs. In this article, you will learn how to use input and output in Dart, a modern and versatile language that can run on multiple platforms.
Dart is a general-purpose, object-oriented, and optionally typed language that supports both compiled and interpreted execution modes. It was developed by Google and is mainly used for web, mobile, and desktop applications. Dart has a rich set of libraries and tools that make it easy to write high-quality and scalable code.
Taking User Input (Standard Input): To read input from the console, you can use the stdin.readLineSync() function. This function allows you to read a line of text entered by the user. Here’s an example of taking a string input from the user: Dart import 'dart:io'; void main() { print("Enter your name:"); String? name = stdin.readLineSync(); print("Hello, $name!\nWelcome to GeeksforGeeks!!"); } AI-generated code. Review and use carefully. More info on FAQ. And here’s an example of taking an integer input: Dart
Output in Dart means sending data or messages to a destination, such as the console, a file, or a network socket. The most common way to output data in Dart is to use the print() function, which writes a string to the standard output stream. For example, you can print a greeting like this: print('Hello, world!'); You can also use string interpolation to insert variables or expressions into a string. For example, you can print the sum of two numbers like this:
var a = 10;
var b = 5;
print('The sum of $a and $b is ${a + b}');
Another way to output data in Dart is to use the write() and writeln() methods of the stdout object, which is part of the dart:io library. These methods are similar to print(), but they allow you to control the formatting and buffering of the output. For example, you can write a string without a newline character like this:
import 'dart:io';
stdout.write('Enter your name: ');
In Dart, you can use input and output through the `stdin` and `stdout` objects from the `dart:io` library. For input: ```dart import 'dart:io'; void main() { stdout.write('Enter your name: '); String name = stdin.readLineSync(); print('Hello, $name!'); } ``` For output: ```dart import 'dart:io'; void main() { String name = 'John'; stdout.write('Hello, $name!'); } ``` Here, `stdout.write()` is used for output, and `stdin.readLineSync()` is used for input.
Input in Dart means receiving data or messages from a source, such as the keyboard, a file, or a network socket. The most common way to input data in Dart is to use the readLineSync() method of the stdin object, which is also part of the dart:io library. This method reads a line of text from the standard input stream and returns it as a string. For example, you can read the user's name and print it like this:
import 'dart:io';
stdout.write('Enter your name: ');
var name = stdin.readLineSync();
print('Hello, $name!');
You can also use the read() and readSync() methods of the stdin object to read bytes from the standard input stream. These methods return a list of integers that represent the ASCII codes of the characters. For example, you can read a single character and print its code like this:
import 'dart:io';
var char = stdin.readSync(1);
print('The code of $char is ${char[0]}');
In Dart, input refers to the reception of data or messages from various sources like the keyboard, files, or network sockets. The readLineSync() method of the stdin object, found in the dart:io library, serves as the primary means to input data. This method retrieves a line of text from the standard input stream and presents it as a string. For instance, to prompt the user for their name and display a greeting, one can employ this method as demonstrated. Additionally, Dart offers read() and readSync() methods within the stdin object, allowing the reading of bytes from the standard input stream. These methods furnish a list of integers signifying the ASCII codes of characters.
Files are another common source and destination of input and output in Dart. The dart:io library provides classes and functions to work with files and directories. To use files in Dart, you need to create a File object with the path of the file as an argument. For example, you can create a File object for a text file named 'test.txt' like this:
import 'dart:io';
var file = File('test.txt');
To write data to a file, you can use the writeAsString() or writeAsBytes() methods of the File object. These methods overwrite the existing content of the file with the given string or list of bytes. For example, you can write a string to the file like this: file.writeAsString('This is a test'); To read data from a file, you can use the readAsString() or readAsBytes() methods of the File object. These methods return the content of the file as a string or a list of bytes. For example, you can read a string from the file like this:
var content = file.readAsString();
print(content);
Sockets are another common source and destination of input and output in Dart. Sockets are endpoints of communication channels that allow data exchange between processes running on different machines or on the same machine. The dart:io library provides classes and functions to work with sockets and network protocols. To use sockets in Dart, you need to create a Socket object with the host and port of the remote endpoint as arguments. For example, you can create a Socket object for a web server running on localhost and port 80 like this:
import 'dart:io';
var socket = await Socket.connect('localhost', 80);
To write data to a socket, you can use the write() or add() methods of the Socket object. These methods send the given string or list of bytes to the remote endpoint. For example, you can write a HTTP request to the socket like this:
socket.write('GET / HTTP/1.1\r\n');
socket.write('Host: localhost\r\n');
socket.write('\r\n');
To read data from a socket, you can use the listen() method of the Socket object. This method registers a callback function that is invoked when data is available on the socket. The callback function receives a list of bytes as an argument. For example, you can print the HTTP response from the socket like this:
socket.listen((data) {
print(String.fromCharCodes(data));
});
In Dart, console input and output is handled by `stdin` and `stdout` from the `dart:io` library. `stdout.writeln` outputs a string to the console, while `stdin.readLineSync` reads a line of text from the console. For file input and output, the `File` class from `dart:io` is used. `file.writeAsStringSync` writes a string to a file, and `file.readAsStringSync` reads the contents of a file as a string. While these are synchronous methods (blocking), Dart also provides asynchronous methods for better performance with large data, as they don't block the program's execution.