Process-termination-handling.md

General

System.CommandLine supports performing actions when the invocation is stopped due to process termination, such as aborting an ongoing transaction or flushing some data to disk.

Process termination can be forceful, which means the process is terminated by the operating system and it doesn't get a chance to clean up. This is killing a process.

Process termination can also be requested, for example when a user presses Ctrl-C on an interactive application or the system asks a service to terminate.

Implementing termination handling

To add termination handling to a command, you must add a CancellationToken argument to the command handler. This token can then be passed along to async APIs that you might call from within your handler. Cancellation actions can also be added directly using the CancellationToken.Register method.

myCommand.Handler = CommandHandler.Create(async (IConsole console, CancellationToken token) =>
{
    try
    {
        using (var httpClient = new HttpClient())
        {
            await httpClient.GetAsync("http://www.example.com", token);
        }
        return 0;
    }
    catch (OperationCanceledException)
    {
        console.Error.WriteLine("The operation was aborted");
        return 1;
    }
});