How to Exit a Dart Application Unconditionally?

The exit() method exits the current program by terminating running Dart VM. This method takes a status code. A non-zero value of status code is generally used to indicate abnormal termination. This is a similar exit in C/C++, Java. This method doesn’t wait for any asynchronous operations to terminate.

Syntax: exit(exit_code);

To use this method we have to import ‘dart:io’ package. The handling of exit codes is platform-specific.

• On Linux and OS, an exit code for normal termination will always be in the range of 0 to 255. If an exit code outside this range is set the actual exit code will be the lower 8 bits masked off and treated as an unsigned value. E.g. using an exit code of -1 will result in an actual exit code of 255 being reported.
• On Windows, the exit code can be set to any 32-bit value. However, some of these values are reserved for reporting system errors like crashes. Besides this, the Dart executable itself uses an exit code of 254 for reporting compile-time errors and an exit code of 255 for reporting runtime error (unhandled exception). Due to these facts, it is recommended to only use exit codes in the range 0 to 127 for communicating the result of running a Dart program to the surrounding environment. This will avoid any cross-platform issues.

Note: The exit(0) Generally used to indicate successful termination while rest generally indicates unsuccessful termination.

Implementation of the exit() method is as:

void exit(int code) {
  ArgumentError.checkNotNull(code, "code");
  if (!_EmbedderConfig._mayExit) {
    throw new UnsupportedError(
        "This embedder disallows calling dart:io's exit()");
  }
  _ProcessUtils._exit(code);
}

Example: Using the exit() method to exit the program abruptly.

Dart

// Importing the packages
import 'dart:io';

// Main Function
void main() {

  // This will be printed
  print("Hello GeeksForGeeks");

  // Standard out code
  exit(0);

  // This will not be printed
  print("Good Bye GeeksForGeeks");
}

Output:

Hello GeeksForGeeks