McMaster.Extensions.CommandLineUtils 4.0.2

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.NET Standard 2.0 .NET Framework 4.5
dotnet add package McMaster.Extensions.CommandLineUtils --version 4.0.2
NuGet\Install-Package McMaster.Extensions.CommandLineUtils -Version 4.0.2
This command is intended to be used within the Package Manager Console in Visual Studio, as it uses the NuGet module's version of Install-Package.
<PackageReference Include="McMaster.Extensions.CommandLineUtils" Version="4.0.2" />
For projects that support PackageReference, copy this XML node into the project file to reference the package.
paket add McMaster.Extensions.CommandLineUtils --version 4.0.2
#r "nuget: McMaster.Extensions.CommandLineUtils, 4.0.2"
#r directive can be used in F# Interactive and Polyglot Notebooks. Copy this into the interactive tool or source code of the script to reference the package.
// Install McMaster.Extensions.CommandLineUtils as a Cake Addin
#addin nuget:?package=McMaster.Extensions.CommandLineUtils&version=4.0.2

// Install McMaster.Extensions.CommandLineUtils as a Cake Tool
#tool nuget:?package=McMaster.Extensions.CommandLineUtils&version=4.0.2


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This project helps you create command line applications using .NET. It simplifies parsing arguments provided on the command line, validating user inputs, and generating help text.

The roadmap for this project is pinned to the top of the issue list.


See documentation for API reference, samples, and tutorials. See also docs/samples/ for more examples, such as:

Installing the library

This project is available as a NuGet package.

$ dotnet add package McMaster.Extensions.CommandLineUtils


CommandLineApplication is the main entry point for most console apps parsing. There are two primary ways to use this API, using the builder pattern and attributes.

Attribute API

using System;
using McMaster.Extensions.CommandLineUtils;

public class Program
    public static int Main(string[] args)
        => CommandLineApplication.Execute<Program>(args);

    [Option(Description = "The subject")]
    public string Subject { get; } = "world";

    [Option(ShortName = "n")]
    public int Count { get; } = 1;

    private void OnExecute()
        for (var i = 0; i < Count; i++)
            Console.WriteLine($"Hello {Subject}!");

Builder API

using System;
using McMaster.Extensions.CommandLineUtils;

var app = new CommandLineApplication();


var subject = app.Option("-s|--subject <SUBJECT>", "The subject", CommandOptionType.SingleValue);
subject.DefaultValue = "world";

var repeat = app.Option<int>("-n|--count <N>", "Repeat", CommandOptionType.SingleValue);
repeat.DefaultValue = 1;

app.OnExecute(() =>
    for (var i = 0; i < repeat.ParsedValue; i++)
        Console.WriteLine($"Hello {subject.Value()}!");

return app.Execute(args);


The library also includes other utilities for interaction with the console. These include:

  • ArgumentEscaper - use to escape arguments when starting a new command line process.
     var args = new [] { "Arg1", "arg with space", "args ' with \" quotes" };
     Process.Start("echo", ArgumentEscaper.EscapeAndConcatenate(args));
  • Prompt - for getting feedback from users with a default answer. A few examples:
    // allows y/n responses, will return false by default in this case.
    // You may optionally change the prompt foreground and background color for
    // the message.
    Prompt.GetYesNo("Do you want to proceed?", false);
    // masks input as '*'
    Prompt.GetPassword("Password: ");
  • DotNetExe - finds the path to the dotnet.exe file used to start a .NET Core process
    Process.Start(DotNetExe.FullPathOrDefault(), "run");

And more! See the documentation for more API, such as IConsole, IReporter, and others.

Getting help

If you need help with this project, please ...

Project origin and status

This is a fork of Microsoft.Extensions.CommandLineUtils, which was completely abandoned by Microsoft. This project forked in 2017 and continued to make improvements. From 2017 to 2021, over 30 contributors added new features and fixed bugs. As of 2022, the project has entered maintenance mode, so no major changes are planned. See this issue for details on latest project status. This project is not abandoned -- I believe this library provides a stable API and rich feature set good enough for most developers to create command line apps in .NET -- but only the most critical of bugs will be fixed (such as security issues).

Product Versions
.NET net5.0 net5.0-windows net6.0 net6.0-android net6.0-ios net6.0-maccatalyst net6.0-macos net6.0-tvos net6.0-windows net7.0 net7.0-android net7.0-ios net7.0-maccatalyst net7.0-macos net7.0-tvos net7.0-windows
.NET Core netcoreapp2.0 netcoreapp2.1 netcoreapp2.2 netcoreapp3.0 netcoreapp3.1
.NET Standard netstandard2.0 netstandard2.1
.NET Framework net45 net451 net452 net46 net461 net462 net463 net47 net471 net472 net48 net481
MonoAndroid monoandroid
MonoMac monomac
MonoTouch monotouch
Tizen tizen40 tizen60
Xamarin.iOS xamarinios
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Xamarin.TVOS xamarintvos
Xamarin.WatchOS xamarinwatchos
Compatible target framework(s)
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Learn more about Target Frameworks and .NET Standard.

NuGet packages (65)

Showing the top 5 NuGet packages that depend on McMaster.Extensions.CommandLineUtils:

Package Downloads
McMaster.Extensions.Hosting.CommandLine The ID prefix of this package has been reserved for one of the owners of this package by

Provides command-line parsing API integration with the generic host API (Microsoft.Extensions.Hosting).

QuantConnect.Configuration The ID prefix of this package has been reserved for one of the owners of this package by

QuantConnect LEAN Engine: Configuration Project - The Config and argument parser implementation


A cross platform build and deployment automation system for building projects and executing deployment scripts using C# code. Documentation can be found at: Detailed examples can be found at:

Microsoft.Jupyter.Core The ID prefix of this package has been reserved for one of the owners of this package by

Provides support for writing Jupyter kernels using the .NET Core SDK.


Provides the ability to provide additional commands to the hosted application by convention

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Version Downloads Last updated
4.0.2 225,238 11/19/2022
4.0.1 1,161,004 2/1/2022
4.0.0 355,212 12/27/2021
4.0.0-beta.74 41,017 1/22/2021
4.0.0-beta.56 1,092 1/17/2021
3.1.0 1,803,330 1/10/2021
3.1.0-rc.371 4,872 11/7/2020
3.1.0-beta.356 1,240 9/13/2020
3.1.0-beta.336 483 8/28/2020
3.0.0 1,942,471 3/29/2020
3.0.0-rc.289 4,807 3/21/2020
3.0.0-alpha.268 2,341 3/9/2020
2.6.0 318,436 3/8/2020
2.5.1 206,883 2/7/2020
2.5.0 192,561 1/2/2020
2.4.4 160,256 11/11/2019
2.4.3 25,575 11/1/2019
2.4.2 137,984 9/24/2019
2.4.1 15,996 9/18/2019
2.4.0 14,656 9/14/2019
2.3.4 909,015 4/11/2019
2.3.3 163,834 3/11/2019
2.3.2 288,577 2/5/2019
2.3.1 37,563 1/19/2019
2.3.0 208,249 1/1/2019
2.2.5 962,550 7/2/2018
2.2.4 109,441 5/25/2018
2.2.3 26,077 5/11/2018
2.2.2 66,435 4/28/2018
2.2.1 89,776 4/11/2018
2.2.0 360,021 3/31/2018
2.2.0-rc 3,372 3/23/2018
2.2.0-beta 1,341 3/8/2018
2.2.0-alpha 1,286 2/20/2018
2.1.1 118,383 12/28/2017
2.1.0 8,229 12/13/2017
2.1.0-rc 1,290 12/7/2017
2.1.0-beta 2,163 11/22/2017
2.1.0-alpha 1,131 11/11/2017
2.0.1 9,891 10/13/2017
2.0.0 9,445 9/16/2017

Changes since 3.1.0:


* @scott-xu and @natemcmaster: feature: add API for setting default value on options and arguments, and display them in help text (#389 and #420)
* @natemcmaster: cleanup: make .Values read-only on CommandArgument/Option (#406)
* @natemcmaster: Make options, arguments, and commands read-only collections on CommandLineApplication (#407)


* @natemcmaster: fix: pass the generic argument version in callback on .Option() and Argument() (#405)
* @natemcmaster: add .NET Standard 2.1 and fix nullable type references (#424 and #425)
* @natemcmaster: fix new CI to correctly publish symbols to
* @scott-xu: show option types in help text when OptionAttribute.Template is set (#429)
* @skirchner989: change to not throw when a validator is not of type AttributeValidator (#431)
* @natemcmaster: don't mask OperationCanceledException triggered by SIGINT (#483)

Updates in 4.0.1 patch:
* @xoofx: use explicit constructors on validation attributes to workaround .NET 6 runtime trimming error (#491)
* @jakubqwe: support the Description field of VersionOptionFromMemberAttribute (#490)

Update in 4.0.2 patch:
* @ernstc: bugfix: added check on the model type before it proceeds accessing the property (#519)

See more details here: