Your first Dart program

Welcome to Dart! In this chapter, you'll ensure your setup is complete, and then work through creating your first Dart program. This chapter starts simple but moves fast!

Before you begin this chapter, ensure you:

• Installed the Dart SDK.
• Reviewed the Dart overview (if you're new to Dart).

First, make sure Dart is ready to go on your system by following these steps.

1. Open a terminal (or command prompt).

2. Run the following command to check your Dart SDK version:

   bash

   dart --version

3. Make sure that you see output similar to this (the version numbers might be different):

   bash

   Dart SDK version: 3.8.0 (stable) (None) on "linux_x64"

   If you see an error like "command not found," refer to the Dart installation guide to set up your environment.

Now, create your first Dart command-line application.

1. In the same terminal, create a new directory called dartpedia to hold your project. Then switch into that directory.

   bash

   mkdir dartpedia
   cd dartpedia

2. Run the following command:

   bash

   dart create cli

   The dart create command generates a basic Dart project named "cli" (for Command Line Interface). It sets up the essential files and directories you need.

3. You should see output similar to this, confirming the project creation:

   bash

   Creating cli using template console...
   
     .gitignore
     analysis_options.yaml
     CHANGELOG.md
     pubspec.yaml
     README.md
     bin/cli.dart
     lib/cli.dart
     test/cli_test.dart
   
   Running pub get...                     1.2s
     Resolving dependencies...
     Downloading packages...
     Changed 49 dependencies!
     1 package has newer versions incompatible with dependency constraints.
     Try `dart pub outdated` for more information.
   
   Created project cli in cli! In order to get started, run the following commands:
   
     cd cli
     dart run

Next, run your program to test it out.

1. In the terminal, navigate into your new project directory:

   bash

   cd cli

2. Run the default application:

   bash

   dart run

   This command tells Dart to execute your program.

3. You should see the following output:

   bash

   Building package executable...
   Built cli:cli.
   Hello world: 42!

   Congratulations! You've successfully run your first Dart program!

Next, modify the code that generated Hello world: 42!.

1. In a code editor, open the bin/cli.dart file.

   The bin/ directory is where your executable code lives. cli.dart is the entry point of your application.

   Inside, you'll see the main function. Every Dart program starts executing from its main function.

2. Check to make sure that your bin/cli.dart looks like this:

   bin/cli.dart

   dart

   import 'package:cli/cli.dart' as cli;
   
   void main(List<String> arguments) {
     print('Hello world: ${cli.calculate()}!');
   }

3. Simplify the output for now. Comment out the first line (you don't need this import statement), and change the print statement to display a simple greeting:

   bin/cli.dart

   dart

   // import 'package:cli/cli.dart' as cli;
   
   void main(List<String> arguments) {
     print('Hello, Dart!'); // Change this line
   }

4. Save your file. Then in the terminal, run your program again:

   bash

   dart run

5. Check to make sure that you see the following:

   bash

   Building package executable...
   Built cli:cli.
   Hello, Dart!

   You've successfully modified and re-run your first Dart program!

In this lesson, you:

• Verified your Dart SDK installation.
• Used dart create to generate a new CLI project.
• Ran your Dart program from the terminal using dart run.
• Identified the main function as the program's entry point within bin/cli.dart.
• Made your first code change and saw the updated output.

Here's a quick quiz to solidify your learning.

Which command is used to create a new Dart project from a template?

• A) dart new
• B) dart build
• C) dart create
• D) dart init

In the next lesson, you'll learn how to make your program respond to specific commands by introducing command-line arguments and the const keyword.