build: initial project release

src/process.dummy.app/.editorconfig

@@ -0,0 +1,6 @@
+
+[*.{cs,vb}]
+# disable IDE0060: Remove unused parameter
+dotnet_diagnostic.IDE0060.severity = none
+# disable IDE0005: Unnecessary using directive
+dotnet_diagnostic.IDE0005.severity = none

src/process.dummy.app/AsyncOutputCommand.cs

@@ -0,0 +1,13 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using Spectre.Console.Cli;
+
+internal abstract class AsyncOutputCommand<T> : AsyncCommand<T> where T : OutputCommandSettings
+{
+}
+
+internal abstract class OutputCommandSettings : CommandSettings
+{
+	[CommandOption("--target")] public OutputTarget Target { get; init; } = OutputTarget.StdOut;
+}

src/process.dummy.app/Geekeey.Process.Dummy.App.csproj

@@ -0,0 +1,17 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net10.0</TargetFramework>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <RootNamespace>Geekeey.Process</RootNamespace>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Spectre.Console" PrivateAssets="compile" />
+    <PackageReference Include="Spectre.Console.Cli" PrivateAssets="compile" />
+  </ItemGroup>
+</Project>

src/process.dummy.app/Output.cs

@@ -0,0 +1,42 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+internal sealed class Output : IDisposable
+{
+	private readonly CancellationTokenSource _cts = new();
+
+	public Output()
+	{
+		Console.CancelKeyPress += Cancel;
+	}
+
+	public StreamReader Stdin { get; } = new(Console.OpenStandardInput(), leaveOpen: false);
+
+	public StreamWriter Stdout { get; } = new(Console.OpenStandardOutput(), leaveOpen: false);
+
+	public StreamWriter Stderr { get; } = new(Console.OpenStandardError(), leaveOpen: false);
+
+	public CancellationToken CancellationToken => _cts.Token;
+
+	public static Output Connect()
+	{
+		return new Output();
+	}
+
+	private void Cancel(object? sender, ConsoleCancelEventArgs args)
+	{
+		args.Cancel = true;
+		_cts.Cancel();
+	}
+
+	public void Dispose()
+	{
+		Stdout.BaseStream.Flush();
+		Stdout.Dispose();
+		Stderr.BaseStream.Flush();
+		Stderr.Dispose();
+		Stdin.Dispose();
+		Console.CancelKeyPress -= Cancel;
+		_cts.Dispose();
+	}
+}

src/process.dummy.app/OutputTarget.cs

@@ -0,0 +1,26 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+[Flags]
+internal enum OutputTarget
+{
+	StdOut = 1,
+	StdErr = 2,
+	All = StdOut | StdErr
+}
+
+internal static class OutputTargetExtensions
+{
+	public static IEnumerable<StreamWriter> GetWriters(this Output output, OutputTarget target)
+	{
+		if (target.HasFlag(OutputTarget.StdOut))
+		{
+			yield return output.Stdout;
+		}
+
+		if (target.HasFlag(OutputTarget.StdErr))
+		{
+			yield return output.Stderr;
+		}
+	}
+}

src/process.dummy.app/Program.cs

@@ -0,0 +1,45 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using System.Reflection;
+using System.Runtime.InteropServices;
+
+using Spectre.Console.Cli;
+
+namespace Geekeey.Process.Testing.Fixture;
+
+public static class Program
+{
+	private static readonly string? FileExtension = RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "exe" : null;
+
+#pragma warning disable IL3000 // only for testing where we don't run in single files!
+	private static readonly string AssemblyPath = Assembly.GetExecutingAssembly().Location;
+#pragma warning restore IL3000
+
+	public static string FilePath { get; } = Path.ChangeExtension(AssemblyPath, FileExtension);
+
+	private static Task<int> Main(string[] args)
+	{
+		Environment.SetEnvironmentVariable("DOTNET_SYSTEM_CONSOLE_ALLOW_ANSI_COLOR_REDIRECTION", "false");
+		var app = new CommandApp();
+		app.Configure(Configuration);
+		return app.RunAsync(args);
+
+		static void Configuration(IConfigurator configuration)
+		{
+			configuration.AddCommand<EchoCommand>("echo");
+			configuration.AddCommand<EchoStdinCommand>("echo-stdin");
+			configuration.AddCommand<EnvironmentCommand>("env");
+			configuration.AddCommand<WorkingDirectoryCommand>("cwd");
+			configuration.AddCommand<WorkingDirectoryCommand>("cwd");
+			configuration.AddCommand<ExitCommand>("exit");
+			configuration.AddCommand<LengthCommand>("length");
+			configuration.AddCommand<SleepCommand>("sleep");
+			configuration.AddBranch("generate", static generate =>
+			{
+				generate.AddCommand<GenerateBlobCommand>("blob");
+				generate.AddCommand<GenerateClobCommand>("clob");
+			});
+		}
+	}
+}

src/process.dummy.app/_commands/EchoCommand.cs

@@ -0,0 +1,25 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using Spectre.Console.Cli;
+
+internal sealed class EchoCommand : AsyncOutputCommand<EchoCommand.Settings>
+{
+	public sealed class Settings : OutputCommandSettings
+	{
+		[CommandOption("--separator <char>")] public string Separator { get; init; } = " ";
+		[CommandArgument(0, "[line]")] public string[] Items { get; init; } = [];
+	}
+
+	public override async Task<int> ExecuteAsync(CommandContext context, Settings settings, CancellationToken cancellationToken)
+	{
+		using var output = Output.Connect();
+
+		foreach (var writer in output.GetWriters(settings.Target))
+		{
+			await writer.WriteLineAsync(string.Join(settings.Separator, settings.Items));
+		}
+
+		return 0;
+	}
+}

src/process.dummy.app/_commands/EchoStdinCommand.cs

@@ -0,0 +1,41 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using System.Buffers;
+
+using Spectre.Console.Cli;
+
+internal sealed class EchoStdinCommand : AsyncOutputCommand<EchoStdinCommand.Settings>
+{
+	public sealed class Settings : OutputCommandSettings
+	{
+		[CommandOption("--length")] public long Length { get; init; } = long.MaxValue;
+	}
+
+	public override async Task<int> ExecuteAsync(CommandContext context, Settings settings, CancellationToken cancellationToken)
+	{
+		using var output = Output.Connect();
+		using var buffer = MemoryPool<byte>.Shared.Rent(81920);
+
+		var count = 0L;
+		while (count < settings.Length)
+		{
+			var bytesWanted = (int)Math.Min(buffer.Memory.Length, settings.Length - count);
+
+			var bytesRead = await output.Stdin.BaseStream.ReadAsync(buffer.Memory[..bytesWanted], cancellationToken);
+			if (bytesRead <= 0)
+			{
+				break;
+			}
+
+			foreach (var writer in output.GetWriters(settings.Target))
+			{
+				await writer.BaseStream.WriteAsync(buffer.Memory[..bytesRead], cancellationToken);
+			}
+
+			count += bytesRead;
+		}
+
+		return 0;
+	}
+}

src/process.dummy.app/_commands/EnvironmentCommand.cs

@@ -0,0 +1,29 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using Spectre.Console.Cli;
+
+internal sealed class EnvironmentCommand : AsyncOutputCommand<EnvironmentCommand.Settings>
+{
+	public sealed class Settings : OutputCommandSettings
+	{
+		[CommandArgument(0, "<ARGUMENT>")] public string[] Variables { get; init; } = [];
+	}
+
+	public override async Task<int> ExecuteAsync(CommandContext context, Settings settings, CancellationToken cancellationToken)
+	{
+		using var output = Output.Connect();
+
+		foreach (var name in settings.Variables)
+		{
+			var value = Environment.GetEnvironmentVariable(name) ?? string.Empty;
+
+			foreach (var writer in output.GetWriters(settings.Target))
+			{
+				await writer.WriteLineAsync(value);
+			}
+		}
+
+		return 0;
+	}
+}

src/process.dummy.app/_commands/ExitCommand.cs

@@ -0,0 +1,21 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using Spectre.Console.Cli;
+
+internal sealed class ExitCommand : AsyncCommand<ExitCommand.Settings>
+{
+	public sealed class Settings : CommandSettings
+	{
+		[CommandArgument(1, "<code>")] public int Code { get; init; }
+	}
+
+	public override async Task<int> ExecuteAsync(CommandContext context, Settings settings, CancellationToken cancellationToken)
+	{
+		using var output = Output.Connect();
+
+		await output.Stderr.WriteLineAsync($"Exit code set to {settings.Code}");
+
+		return settings.Code;
+	}
+}

src/process.dummy.app/_commands/GenerateBlobCommand.cs

@@ -0,0 +1,40 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using System.Buffers;
+
+using Spectre.Console.Cli;
+
+internal sealed class GenerateBlobCommand : AsyncOutputCommand<GenerateBlobCommand.Settings>
+{
+	private readonly Random _random = new(1234567);
+
+	public sealed class Settings : OutputCommandSettings
+	{
+		[CommandOption("--length")] public long Length { get; init; } = 100_000;
+		[CommandOption("--buffer")] public int BufferSize { get; init; } = 1024;
+	}
+
+	public override async Task<int> ExecuteAsync(CommandContext context, Settings settings, CancellationToken cancellationToken)
+	{
+		using var output = Output.Connect();
+
+		using var bytes = MemoryPool<byte>.Shared.Rent(settings.BufferSize);
+
+		var total = 0L;
+		while (total < settings.Length)
+		{
+			_random.NextBytes(bytes.Memory.Span);
+
+			var count = (int)Math.Min(bytes.Memory.Length, settings.Length - total);
+			foreach (var writer in output.GetWriters(settings.Target))
+			{
+				await writer.BaseStream.WriteAsync(bytes.Memory[..count], cancellationToken);
+			}
+
+			total += count;
+		}
+
+		return 0;
+	}
+}

src/process.dummy.app/_commands/GenerateClobCommand.cs

@@ -0,0 +1,42 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using System.Text;
+
+using Spectre.Console.Cli;
+
+internal sealed class GenerateClobCommand : AsyncOutputCommand<GenerateClobCommand.Settings>
+{
+	private readonly Random _random = new(1234567);
+	private readonly char[] _chars = [.. Enumerable.Range(32, 94).Select(i => (char)i)];
+
+	public sealed class Settings : OutputCommandSettings
+	{
+		[CommandOption("--length")] public int Length { get; init; } = 100_000;
+		[CommandOption("--lines")] public int LinesCount { get; init; } = 1;
+	}
+
+	public override async Task<int> ExecuteAsync(CommandContext context, Settings settings, CancellationToken cancellationToken)
+	{
+		using var output = Output.Connect();
+
+		var buffer = new StringBuilder(settings.Length);
+
+		for (var line = 0; line < settings.LinesCount; line++)
+		{
+			buffer.Clear();
+
+			for (var i = 0; i < settings.Length; i++)
+			{
+				buffer.Append(_chars[_random.Next(0, _chars.Length)]);
+			}
+
+			foreach (var writer in output.GetWriters(settings.Target))
+			{
+				await writer.WriteLineAsync(buffer.ToString());
+			}
+		}
+
+		return 0;
+	}
+}

src/process.dummy.app/_commands/LengthCommand.cs

@@ -0,0 +1,40 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using System.Buffers;
+using System.Globalization;
+
+using Spectre.Console.Cli;
+
+internal sealed class LengthCommand : AsyncOutputCommand<LengthCommand.Settings>
+{
+	public sealed class Settings : OutputCommandSettings
+	{
+	}
+
+	public override async Task<int> ExecuteAsync(CommandContext context, Settings settings, CancellationToken cancellationToken)
+	{
+		using var output = Output.Connect();
+
+		using var buffer = MemoryPool<byte>.Shared.Rent(81920);
+
+		var count = 0L;
+		while (true)
+		{
+			var bytesRead = await output.Stdin.BaseStream.ReadAsync(buffer.Memory, cancellationToken);
+			if (bytesRead <= 0)
+			{
+				break;
+			}
+
+			count += bytesRead;
+		}
+
+		foreach (var writer in output.GetWriters(settings.Target))
+		{
+			await writer.WriteLineAsync(count.ToString(CultureInfo.InvariantCulture));
+		}
+
+		return 0;
+	}
+}

src/process.dummy.app/_commands/SleepCommand.cs

@@ -0,0 +1,34 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using Spectre.Console.Cli;
+
+internal sealed class SleepCommand : AsyncCommand<SleepCommand.Settings>
+{
+	public sealed class Settings : CommandSettings
+	{
+		[CommandArgument(0, "[duration]")] public TimeSpan Duration { get; init; } = TimeSpan.FromSeconds(1);
+	}
+
+	public override async Task<int> ExecuteAsync(CommandContext context, Settings settings, CancellationToken cancellationToken)
+	{
+		using var output = Output.Connect();
+
+		try
+		{
+			await Console.Out.WriteLineAsync($"Sleeping for {settings.Duration}...");
+			await Console.Out.FlushAsync(CancellationToken.None);
+
+			await Task.Delay(settings.Duration, output.CancellationToken);
+		}
+		catch (OperationCanceledException)
+		{
+			await Console.Out.WriteLineAsync("Canceled.");
+			await Console.Out.FlushAsync(CancellationToken.None);
+		}
+
+		await Console.Out.WriteLineAsync("Done.");
+		await Console.Out.FlushAsync(CancellationToken.None);
+		return 0;
+	}
+}

src/process.dummy.app/_commands/WorkingDirectoryCommand.cs

@@ -0,0 +1,23 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using Spectre.Console.Cli;
+
+internal sealed class WorkingDirectoryCommand : AsyncOutputCommand<WorkingDirectoryCommand.Settings>
+{
+	public sealed class Settings : OutputCommandSettings
+	{
+	}
+
+	public override async Task<int> ExecuteAsync(CommandContext context, Settings settings, CancellationToken cancellationToken)
+	{
+		using var output = Output.Connect();
+
+		foreach (var writer in output.GetWriters(settings.Target))
+		{
+			await writer.WriteLineAsync(Directory.GetCurrentDirectory());
+		}
+
+		return 0;
+	}
+}

src/process.tests/.editorconfig

@@ -0,0 +1,6 @@
+
+[*.{cs,vb}]
+# disable IDE0060: Remove unused parameter
+dotnet_diagnostic.IDE0060.severity = none
+# disable IDE0005: Unnecessary using directive
+dotnet_diagnostic.IDE0005.severity = none

src/process.tests/CancellationTests.cs

@@ -0,0 +1,181 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using System.Text;
+
+using Geekeey.Process.Buffered;
+
+namespace Geekeey.Process.Tests;
+
+internal sealed class CancellationTests
+{
+	private static Action<string> NotifyOnStart(out TaskCompletionSource tcs)
+	{
+		// run the continuation async on the thread pool to allow the io reader to complete
+		var source = tcs = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
+		return line =>
+		{
+			if (line.Contains("Sleeping for", StringComparison.OrdinalIgnoreCase))
+			{
+				source.TrySetResult();
+			}
+		};
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_and_cancel_it_immediately()
+	{
+		// Arrange
+		using var cts = new CancellationTokenSource();
+
+		var stdout = new StringBuilder();
+
+		var target = PipeTarget.Merge(
+			PipeTarget.ToDelegate(NotifyOnStart(out var tcs)),
+			PipeTarget.ToStringBuilder(stdout)
+		);
+
+		var cmd = new Command(Testing.Fixture.Program.FilePath)
+					  .WithArguments(["sleep", "00:00:30"]) |
+				  target;
+
+		// Act
+		var task = cmd.ExecuteAsync(cts.Token);
+		await tcs.Task;
+		await cts.CancelAsync();
+
+		// Assert
+		await Assert.That(async () => await task).Throws<OperationCanceledException>();
+
+		using (Assert.Multiple())
+		{
+			await Assert.That(ProcessTree.HasExited(task.ProcessId)).IsTrue();
+			await Assert.That(stdout.ToString()).Contains("Sleeping for");
+			await Assert.That(stdout.ToString()).DoesNotContain("Done.");
+		}
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_and_kill_it_immediately()
+	{
+		// Arrange
+		var stdout = new StringBuilder();
+
+		var target = PipeTarget.Merge(
+			PipeTarget.ToDelegate(NotifyOnStart(out var tcs)),
+			PipeTarget.ToStringBuilder(stdout)
+		);
+
+		var cmd = new Command(Testing.Fixture.Program.FilePath)
+					  .WithArguments(["sleep", "00:00:30"]) |
+				  target;
+
+		// Act
+		var task = cmd.ExecuteAsync();
+		await tcs.Task;
+		task.Kill();
+
+		// Assert
+		await Assert.That(async () => await task).Throws<CommandExecutionException>();
+
+		using (Assert.Multiple())
+		{
+			await Assert.That(ProcessTree.HasExited(task.ProcessId)).IsTrue();
+			await Assert.That(stdout.ToString()).Contains("Sleeping for");
+			await Assert.That(stdout.ToString()).DoesNotContain("Done.");
+		}
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_with_buffering_and_kill_it_immediately()
+	{
+		// Arrange
+		var stdout = new StringBuilder();
+
+		var target = PipeTarget.Merge(
+			PipeTarget.ToDelegate(NotifyOnStart(out var tcs)),
+			PipeTarget.ToStringBuilder(stdout)
+		);
+
+		var cmd = new Command(Testing.Fixture.Program.FilePath)
+					  .WithArguments(["sleep", "00:00:30"]) |
+				  target;
+
+		// Act
+		var task = cmd.ExecuteBufferedAsync();
+		await tcs.Task;
+		task.Kill();
+
+		// Assert
+		await Assert.That(async () => await task).Throws<CommandExecutionException>();
+
+		using (Assert.Multiple())
+		{
+			await Assert.That(ProcessTree.HasExited(task.ProcessId)).IsTrue();
+			await Assert.That(stdout.ToString()).Contains("Sleeping for");
+			await Assert.That(stdout.ToString()).DoesNotContain("Done.");
+		}
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_and_interrupt_it_immediately()
+	{
+		// Arrange
+		var stdout = new StringBuilder();
+
+		var target = PipeTarget.Merge(
+			PipeTarget.ToDelegate(NotifyOnStart(out var tcs)),
+			PipeTarget.ToStringBuilder(stdout)
+		);
+
+		var cmd = new Command(Testing.Fixture.Program.FilePath)
+					  .WithArguments(["sleep", "00:00:30"]) |
+				  target;
+
+		// Act
+		var task = cmd.ExecuteAsync();
+		await tcs.Task;
+		task.Interrupt();
+
+		// Assert
+		await Assert.That(async () => await task).ThrowsNothing();
+
+		using (Assert.Multiple())
+		{
+			await Assert.That(ProcessTree.HasExited(task.ProcessId)).IsTrue();
+			await Assert.That(stdout.ToString()).Contains("Sleeping for");
+			await Assert.That(stdout.ToString()).Contains("Done.");
+		}
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_with_buffering_and_interrupt_it_immediately()
+	{
+		// Arrange
+		var stdout = new StringBuilder();
+
+		var target = PipeTarget.Merge(
+			PipeTarget.ToDelegate(NotifyOnStart(out var tcs)),
+			PipeTarget.ToStringBuilder(stdout)
+		);
+
+		var cmd = new Command(Testing.Fixture.Program.FilePath)
+					  .WithArguments(["sleep", "00:00:30"]) |
+				  target;
+
+		// Act
+		var task = cmd.ExecuteBufferedAsync();
+		await tcs.Task;
+		task.Interrupt();
+
+		// Assert
+		await Assert.That(async () => await task).ThrowsNothing();
+
+		using (Assert.Multiple())
+		{
+			await Assert.That(ProcessTree.HasExited(task.ProcessId)).IsTrue();
+			await Assert.That(stdout.ToString()).Contains("Sleeping for");
+			await Assert.That(stdout.ToString()).Contains("Done.");
+		}
+	}
+}

src/process.tests/CommandTests.cs

@@ -0,0 +1,273 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+namespace Geekeey.Process.Tests;
+
+internal sealed class CommandTests
+{
+	[Test]
+	public async Task I_can_create_a_command_with_the_default_configuration()
+	{
+		var cmd = new Command("foo");
+
+		using (Assert.Multiple())
+		{
+			await Assert.That(cmd.TargetFilePath).IsEqualTo("foo");
+			await Assert.That(cmd.Arguments).IsEmpty();
+			await Assert.That(cmd.WorkingDirPath).IsEqualTo(Directory.GetCurrentDirectory());
+			await Assert.That(cmd.Environment).IsEmpty();
+			await Assert.That(cmd.Validation).HasFlag(ValidationMode.ZeroExitCode);
+			await Assert.That(cmd.StandardInputPipe).IsEqualTo(PipeSource.Null);
+			await Assert.That(cmd.StandardOutputPipe).IsEqualTo(PipeTarget.Null);
+			await Assert.That(cmd.StandardErrorPipe).IsEqualTo(PipeTarget.Null);
+		}
+	}
+
+	[Test]
+	public async Task I_can_configure_the_target_file()
+	{
+		var cmd = new Command("foo");
+		var modified = cmd.WithTargetFile("bar");
+
+		using (Assert.Multiple())
+		{
+			await Assert.That(modified.TargetFilePath).IsEqualTo("bar");
+			await Assert.That(modified.Arguments).IsEqualTo(cmd.Arguments);
+			await Assert.That(modified.WorkingDirPath).IsEqualTo(cmd.WorkingDirPath);
+			await Assert.That(modified.Environment).IsEqualTo(cmd.Environment);
+			await Assert.That(modified.Validation).IsEqualTo(cmd.Validation);
+			await Assert.That(modified.StandardInputPipe).IsEqualTo(cmd.StandardInputPipe);
+			await Assert.That(modified.StandardOutputPipe).IsEqualTo(cmd.StandardOutputPipe);
+			await Assert.That(modified.StandardErrorPipe).IsEqualTo(cmd.StandardErrorPipe);
+			await Assert.That(cmd.TargetFilePath).IsNotEqualTo("bar");
+		}
+	}
+
+	[Test]
+	public async Task I_can_configure_the_command_line_arguments()
+	{
+		var cmd = new Command("foo").WithArguments("xxx");
+		var modified = cmd.WithArguments("abc def");
+
+		using (Assert.Multiple())
+		{
+			await Assert.That(modified.TargetFilePath).IsEqualTo(cmd.TargetFilePath);
+			await Assert.That(modified.Arguments).IsEqualTo("abc def");
+			await Assert.That(modified.WorkingDirPath).IsEqualTo(cmd.WorkingDirPath);
+			await Assert.That(modified.Environment).IsEqualTo(cmd.Environment);
+			await Assert.That(modified.Validation).IsEqualTo(cmd.Validation);
+			await Assert.That(modified.StandardInputPipe).IsEqualTo(cmd.StandardInputPipe);
+			await Assert.That(modified.StandardOutputPipe).IsEqualTo(cmd.StandardOutputPipe);
+			await Assert.That(modified.StandardErrorPipe).IsEqualTo(cmd.StandardErrorPipe);
+			await Assert.That(cmd.Arguments).IsNotEqualTo("abc def");
+		}
+	}
+
+	[Test]
+	public async Task I_can_configure_the_command_line_arguments_by_passing_an_array()
+	{
+		var cmd = new Command("foo").WithArguments("xxx");
+		var modified = cmd.WithArguments(["abc", "def"]);
+
+		using (Assert.Multiple())
+		{
+			await Assert.That(modified.TargetFilePath).IsEqualTo(cmd.TargetFilePath);
+			await Assert.That(modified.Arguments).IsEqualTo("abc def");
+			await Assert.That(modified.WorkingDirPath).IsEqualTo(cmd.WorkingDirPath);
+			await Assert.That(modified.Environment).IsEqualTo(cmd.Environment);
+			await Assert.That(modified.Validation).IsEqualTo(cmd.Validation);
+			await Assert.That(modified.StandardInputPipe).IsEqualTo(cmd.StandardInputPipe);
+			await Assert.That(modified.StandardOutputPipe).IsEqualTo(cmd.StandardOutputPipe);
+			await Assert.That(modified.StandardErrorPipe).IsEqualTo(cmd.StandardErrorPipe);
+			await Assert.That(cmd.Arguments).IsNotEqualTo("abc def");
+		}
+	}
+
+	[Test]
+	public async Task I_can_configure_the_command_line_arguments_using_a_builder()
+	{
+		var cmd = new Command("foo").WithArguments("xxx");
+		var modified = cmd.WithArguments(args => args
+			.Add("-a")
+			.Add("foo bar")
+			.Add("\"foo\\\\bar\"")
+			.Add(3.14)
+			.Add(["foo", "bar"])
+			.Add([-10, 12.12]));
+
+		using (Assert.Multiple())
+		{
+			await Assert.That(modified.TargetFilePath).IsEqualTo(cmd.TargetFilePath);
+			await Assert.That(modified.Arguments).IsEqualTo("-a \"foo bar\" \"\\\"foo\\\\bar\\\"\" 3.14 foo bar -10 12.12");
+			await Assert.That(modified.WorkingDirPath).IsEqualTo(cmd.WorkingDirPath);
+			await Assert.That(modified.Environment).IsEqualTo(cmd.Environment);
+			await Assert.That(modified.Validation).IsEqualTo(cmd.Validation);
+			await Assert.That(modified.StandardInputPipe).IsEqualTo(cmd.StandardInputPipe);
+			await Assert.That(modified.StandardOutputPipe).IsEqualTo(cmd.StandardOutputPipe);
+			await Assert.That(modified.StandardErrorPipe).IsEqualTo(cmd.StandardErrorPipe);
+			await Assert.That(cmd.Arguments).IsNotEqualTo("-a \"foo bar\" \"\\\"foo\\\\bar\\\"\" 3.14 foo bar -10 12.12");
+		}
+	}
+
+	[Test]
+	public async Task I_can_configure_the_working_directory()
+	{
+		var cmd = new Command("foo").WithWorkingDirectory("xxx");
+		var modified = cmd.WithWorkingDirectory("new");
+
+		using (Assert.Multiple())
+		{
+			await Assert.That(modified.TargetFilePath).IsEqualTo(cmd.TargetFilePath);
+			await Assert.That(modified.Arguments).IsEqualTo(cmd.Arguments);
+			await Assert.That(modified.WorkingDirPath).IsEqualTo("new");
+			await Assert.That(modified.Environment).IsEqualTo(cmd.Environment);
+			await Assert.That(modified.Validation).IsEqualTo(cmd.Validation);
+			await Assert.That(modified.StandardInputPipe).IsEqualTo(cmd.StandardInputPipe);
+			await Assert.That(modified.StandardOutputPipe).IsEqualTo(cmd.StandardOutputPipe);
+			await Assert.That(modified.StandardErrorPipe).IsEqualTo(cmd.StandardErrorPipe);
+			await Assert.That(cmd.WorkingDirPath).IsNotEqualTo("new");
+		}
+	}
+
+	[Test]
+	public async Task I_can_configure_the_environment_variables()
+	{
+		var cmd = new Command("foo").WithEnvironment(e => e.Set("xxx", "xxx"));
+		var vars = new Dictionary<string, string?>
+		{
+			["name"] = "value",
+			["key"] = "door",
+		};
+		var modified = cmd.WithEnvironment(vars);
+
+		using (Assert.Multiple())
+		{
+			await Assert.That(modified.TargetFilePath).IsEqualTo(cmd.TargetFilePath);
+			await Assert.That(modified.Arguments).IsEqualTo(cmd.Arguments);
+			await Assert.That(modified.WorkingDirPath).IsEqualTo(cmd.WorkingDirPath);
+			await Assert.That(modified.Environment).IsEqualTo(vars);
+			await Assert.That(modified.Validation).IsEqualTo(cmd.Validation);
+			await Assert.That(modified.StandardInputPipe).IsEqualTo(cmd.StandardInputPipe);
+			await Assert.That(modified.StandardOutputPipe).IsEqualTo(cmd.StandardOutputPipe);
+			await Assert.That(modified.StandardErrorPipe).IsEqualTo(cmd.StandardErrorPipe);
+			await Assert.That(cmd.Environment).IsNotEqualTo(vars);
+		}
+	}
+
+	[Test]
+	public async Task I_can_configure_the_environment_variables_using_a_builder()
+	{
+		var cmd = new Command("foo").WithEnvironment(e => e.Set("xxx", "xxx"));
+		var modified = cmd.WithEnvironment(env => env
+			.Set("name", "value")
+			.Set("key", "door")
+			.Set(new Dictionary<string, string?>
+			{
+				["zzz"] = "yyy",
+				["aaa"] = "bbb",
+			}));
+
+		using (Assert.Multiple())
+		{
+			var vars = new Dictionary<string, string?>
+			{
+				["name"] = "value",
+				["key"] = "door",
+				["zzz"] = "yyy",
+				["aaa"] = "bbb",
+			};
+			await Assert.That(modified.TargetFilePath).IsEqualTo(cmd.TargetFilePath);
+			await Assert.That(modified.Arguments).IsEqualTo(cmd.Arguments);
+			await Assert.That(modified.WorkingDirPath).IsEqualTo(cmd.WorkingDirPath);
+			await Assert.That(modified.Environment).IsEquivalentTo(vars);
+			await Assert.That(modified.Validation).IsEqualTo(cmd.Validation);
+			await Assert.That(modified.StandardInputPipe).IsEqualTo(cmd.StandardInputPipe);
+			await Assert.That(modified.StandardOutputPipe).IsEqualTo(cmd.StandardOutputPipe);
+			await Assert.That(modified.StandardErrorPipe).IsEqualTo(cmd.StandardErrorPipe);
+			await Assert.That(cmd.Environment).IsNotEqualTo(vars);
+		}
+	}
+
+	[Test]
+	public async Task I_can_configure_the_result_validation_strategy()
+	{
+		var cmd = new Command("foo").WithExitValidation(ValidationMode.ZeroExitCode);
+		var modified = cmd.WithExitValidation(ValidationMode.None);
+
+		using (Assert.Multiple())
+		{
+			await Assert.That(modified.TargetFilePath).IsEqualTo(cmd.TargetFilePath);
+			await Assert.That(modified.Arguments).IsEqualTo(cmd.Arguments);
+			await Assert.That(modified.WorkingDirPath).IsEqualTo(cmd.WorkingDirPath);
+			await Assert.That(modified.Environment).IsEqualTo(cmd.Environment);
+			await Assert.That(modified.Validation).IsEqualTo(ValidationMode.None);
+			await Assert.That(modified.StandardInputPipe).IsEqualTo(cmd.StandardInputPipe);
+			await Assert.That(modified.StandardOutputPipe).IsEqualTo(cmd.StandardOutputPipe);
+			await Assert.That(modified.StandardErrorPipe).IsEqualTo(cmd.StandardErrorPipe);
+			await Assert.That(cmd.Validation).IsNotEqualTo(ValidationMode.None);
+		}
+	}
+
+	[Test]
+	public async Task I_can_configure_the_stdin_pipe()
+	{
+		var cmd = new Command("foo").WithStandardInputPipe(PipeSource.Null);
+		var pipeSource = PipeSource.FromStream(Stream.Null);
+		var modified = cmd.WithStandardInputPipe(pipeSource);
+
+		using (Assert.Multiple())
+		{
+			await Assert.That(modified.TargetFilePath).IsEqualTo(cmd.TargetFilePath);
+			await Assert.That(modified.Arguments).IsEqualTo(cmd.Arguments);
+			await Assert.That(modified.WorkingDirPath).IsEqualTo(cmd.WorkingDirPath);
+			await Assert.That(modified.Environment).IsEqualTo(cmd.Environment);
+			await Assert.That(modified.Validation).IsEqualTo(cmd.Validation);
+			await Assert.That(modified.StandardInputPipe).IsEqualTo(pipeSource);
+			await Assert.That(modified.StandardOutputPipe).IsEqualTo(cmd.StandardOutputPipe);
+			await Assert.That(modified.StandardErrorPipe).IsEqualTo(cmd.StandardErrorPipe);
+			await Assert.That(cmd.StandardInputPipe).IsNotEqualTo(pipeSource);
+		}
+	}
+
+	[Test]
+	public async Task I_can_configure_the_stdout_pipe()
+	{
+		var cmd = new Command("foo").WithStandardOutputPipe(PipeTarget.Null);
+		var pipeTarget = PipeTarget.ToStream(Stream.Null);
+		var modified = cmd.WithStandardOutputPipe(pipeTarget);
+
+		using (Assert.Multiple())
+		{
+			await Assert.That(modified.TargetFilePath).IsEqualTo(cmd.TargetFilePath);
+			await Assert.That(modified.Arguments).IsEqualTo(cmd.Arguments);
+			await Assert.That(modified.WorkingDirPath).IsEqualTo(cmd.WorkingDirPath);
+			await Assert.That(modified.Environment).IsEqualTo(cmd.Environment);
+			await Assert.That(modified.Validation).IsEqualTo(cmd.Validation);
+			await Assert.That(modified.StandardInputPipe).IsEqualTo(cmd.StandardInputPipe);
+			await Assert.That(modified.StandardOutputPipe).IsEqualTo(pipeTarget);
+			await Assert.That(modified.StandardErrorPipe).IsEqualTo(cmd.StandardErrorPipe);
+			await Assert.That(cmd.StandardOutputPipe).IsNotEqualTo(pipeTarget);
+		}
+	}
+
+	[Test]
+	public async Task I_can_configure_the_stderr_pipe()
+	{
+		var cmd = new Command("foo").WithStandardErrorPipe(PipeTarget.Null);
+		var pipeTarget = PipeTarget.ToStream(Stream.Null);
+		var modified = cmd.WithStandardErrorPipe(pipeTarget);
+
+		using (Assert.Multiple())
+		{
+			await Assert.That(modified.TargetFilePath).IsEqualTo(cmd.TargetFilePath);
+			await Assert.That(modified.Arguments).IsEqualTo(cmd.Arguments);
+			await Assert.That(modified.WorkingDirPath).IsEqualTo(cmd.WorkingDirPath);
+			await Assert.That(modified.Environment).IsEqualTo(cmd.Environment);
+			await Assert.That(modified.Validation).IsEqualTo(cmd.Validation);
+			await Assert.That(modified.StandardInputPipe).IsEqualTo(cmd.StandardInputPipe);
+			await Assert.That(modified.StandardOutputPipe).IsEqualTo(cmd.StandardOutputPipe);
+			await Assert.That(modified.StandardErrorPipe).IsEqualTo(pipeTarget);
+			await Assert.That(cmd.StandardErrorPipe).IsNotEqualTo(pipeTarget);
+		}
+	}
+}

src/process.tests/ExecuteTests.cs

@@ -0,0 +1,139 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using Geekeey.Process.Buffered;
+
+namespace Geekeey.Process.Tests;
+
+internal sealed class ExecuteTests
+{
+	[Test]
+	public async Task I_can_execute_a_command_and_get_the_exit_code_and_execution_time()
+	{
+		// Arrange
+		var cmd = new Command(Testing.Fixture.Program.FilePath)
+			.WithArguments(["echo"]);
+
+		// Act
+		var result = await cmd.ExecuteAsync();
+
+		await Assert.That(result.ExitCode).IsZero();
+
+		// Assert
+		using (Assert.Multiple())
+		{
+			await Assert.That(result.ExitCode).IsZero();
+			await Assert.That(result.IsSuccess).IsTrue();
+			await Assert.That(result.RunTime).IsGreaterThan(TimeSpan.Zero);
+		}
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_and_get_the_associated_process_id()
+	{
+		// Arrange
+		var cmd = new Command(Testing.Fixture.Program.FilePath)
+			.WithArguments(["echo"]);
+
+		// Act
+		var task = cmd.ExecuteAsync();
+
+		// Assert
+		await Assert.That(task.ProcessId).IsNotZero();
+
+		await task;
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_with_a_configured_awaiter()
+	{
+		// Arrange
+		var cmd = new Command(Testing.Fixture.Program.FilePath)
+			.WithArguments(["echo"]);
+
+		// Act + Assert
+		await cmd.ExecuteAsync().ConfigureAwait(false);
+	}
+
+	[Test]
+	public async Task I_can_try_to_execute_a_command_and_get_an_error_if_the_target_file_does_not_exist()
+	{
+		// Arrange
+		var cmd = new Command("some_exe_with_does_not_exits");
+
+		// Act + Assert
+		await Assert.That(() => cmd.ExecuteAsync()).Throws<InvalidOperationException>()
+			.WithInnerException();
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_with_a_custom_working_directory()
+	{
+		// Arrange
+		using var dir = TestTempDirectory.Create();
+
+		var cmd = new Command(Testing.Fixture.Program.FilePath)
+			.WithArguments("cwd")
+			.WithWorkingDirectory(dir.Path);
+
+		// Act
+		var result = await cmd.ExecuteBufferedAsync();
+
+		await Assert.That(result.ExitCode).IsZero();
+
+		// Assert
+		var lines = result.StandardOutput.Split(Environment.NewLine);
+		await Assert.That(lines).Contains(dir.Path);
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_with_additional_environment_variables()
+	{
+		// Arrange
+		var cmd = new Command(Testing.Fixture.Program.FilePath)
+			.WithArguments(["env", "foo", "bar"])
+			.WithEnvironment(env => env
+				.Set("foo", "hello")
+				.Set("bar", "world"));
+
+		// Act
+		var result = await cmd.ExecuteBufferedAsync();
+
+		await Assert.That(result.ExitCode).IsZero();
+
+		// Assert
+		var lines = result.StandardOutput.Split(Environment.NewLine);
+		await Assert.That(lines).Contains("hello");
+		await Assert.That(lines).Contains("world");
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_with_some_environment_variables_overwritten()
+	{
+		// Arrange
+		var key = Guid.NewGuid();
+		var variableToKeep = $"GKY_TEST_KEEP_{key}";
+		var variableToOverwrite = $"GKY_TEST_OVERWRITE_{key}";
+		var variableToUnset = $"GKY_TEST_UNSET_{key}";
+
+		using var a = TestEnvironment.Create(variableToKeep, "keep");
+		using var b = TestEnvironment.Create(variableToOverwrite, "overwrite");
+		using var c = TestEnvironment.Create(variableToUnset, "unset");
+
+		var cmd = new Command(Testing.Fixture.Program.FilePath)
+			.WithArguments(["env", variableToKeep, variableToOverwrite, variableToUnset])
+			.WithEnvironment(env => env
+				.Set(variableToOverwrite, "overwritten")
+				.Set(variableToUnset, null));
+
+		// Act
+		var result = await cmd.ExecuteBufferedAsync();
+
+		await Assert.That(result.ExitCode).IsZero();
+
+		// Assert
+		var lines = result.StandardOutput.Split(Environment.NewLine);
+		await Assert.That(lines).Contains("keep");
+		await Assert.That(lines).Contains("overwritten");
+	}
+}

src/process.tests/Geekeey.Process.Tests.csproj

@@ -0,0 +1,18 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net10.0</TargetFramework>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="TUnit" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\process\Geekeey.Process.csproj" />
+    <ProjectReference Include="..\process.dummy.app\Geekeey.Process.Dummy.App.csproj" />
+  </ItemGroup>
+
+</Project>

src/process.tests/LineBreakTests.cs

@@ -0,0 +1,81 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+namespace Geekeey.Process.Tests;
+
+internal sealed class LineBreakTests
+{
+	private static Command Echo()
+	{
+		return new Command(Testing.Fixture.Program.FilePath)
+			.WithArguments("echo-stdin");
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_and_split_the_stdout_by_newline()
+	{
+		// Arrange
+		const string data = "Foo\nBar\nBaz";
+
+		var stdOutLines = new List<string>();
+
+		var cmd = data | Echo() | stdOutLines.Add;
+
+		// Act
+		await cmd.ExecuteAsync();
+
+		// Assert
+		await Assert.That(stdOutLines).IsEquivalentTo(["Foo", "Bar", "Baz"]);
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_and_split_the_stdout_by_caret_return()
+	{
+		// Arrange
+		const string data = "Foo\rBar\rBaz";
+
+		var stdOutLines = new List<string>();
+
+		var cmd = data | Echo() | stdOutLines.Add;
+
+		// Act
+		await cmd.ExecuteAsync();
+
+		// Assert
+		await Assert.That(stdOutLines).IsEquivalentTo(["Foo", "Bar", "Baz"]);
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_and_split_the_stdout_by_caret_return_followed_by_newline()
+	{
+		// Arrange
+		const string data = "Foo\r\nBar\r\nBaz";
+
+		var stdOutLines = new List<string>();
+
+		var cmd = data | Echo() | stdOutLines.Add;
+
+		// Act
+		await cmd.ExecuteAsync();
+
+		// Assert
+		await Assert.That(stdOutLines).IsEquivalentTo(["Foo", "Bar", "Baz"]);
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_and_split_the_stdout_by_newline_while_including_empty_lines()
+	{
+		// Arrange
+		const string data = "Foo\r\rBar\n\nBaz";
+
+		var stdOutLines = new List<string>();
+
+		var cmd = data | Echo() | stdOutLines.Add;
+
+		// Act
+		await cmd.ExecuteAsync();
+
+		// Assert
+		await Assert.That(stdOutLines).IsEquivalentTo(["Foo", "", "Bar", "", "Baz"]);
+	}
+}

src/process.tests/PathResolutionTests.cs

@@ -0,0 +1,50 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using Geekeey.Process.Buffered;
+
+namespace Geekeey.Process.Tests;
+
+internal sealed class PathResolutionTests
+{
+	[Test]
+	public async Task I_can_execute_a_command_on_an_executable_using_its_short_name()
+	{
+		// Arrange
+		var cmd = new Command("dotnet")
+			.WithArguments("--version");
+
+		// Act
+		var result = await cmd.ExecuteBufferedAsync();
+
+		// Assert
+		using (Assert.Multiple())
+		{
+			await Assert.That(result.ExitCode).IsEqualTo(0);
+			await Assert.That(result.StandardOutput.Trim()).Matches(@"^\d+\.\d+\.\d+$");
+		}
+	}
+
+	[Test]
+	[Platform(PlatformAttribute.Windows)]
+	public async Task I_can_execute_a_command_on_a_script_using_its_short_name()
+	{
+		// Arrange
+		using var dir = TestTempDirectory.Create();
+		await File.WriteAllTextAsync(Path.Combine(dir.Path, "script.cmd"), "@echo hi");
+
+		using var _1 = TestEnvironment.ExtendPath(dir.Path);
+		var cmd = new Command("script");
+
+		// Act
+		var result = await cmd.ExecuteBufferedAsync();
+
+		// Assert
+		// Assert
+		using (Assert.Multiple())
+		{
+			await Assert.That(result.ExitCode).IsEqualTo(0);
+			await Assert.That(result.StandardOutput.Trim()).IsEqualTo("hi");
+		}
+	}
+}

src/process.tests/PipingTests.cs

@@ -0,0 +1,536 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using System.Text;
+
+using Geekeey.Process.Buffered;
+
+namespace Geekeey.Process.Tests;
+
+internal sealed class PipingTests
+{
+	#region Stdin
+
+	[Test]
+	public async Task I_can_execute_a_command_and_pipe_the_stdin_from_an_async_anonymous_source()
+	{
+		// Arrange
+		var source = PipeSource.Create(async (destination, cancellationToken)
+			=> await destination.WriteAsync("Hello World!"u8.ToArray(), cancellationToken));
+
+		var cmd = source |
+				  new Command(Testing.Fixture.Program.FilePath)
+					  .WithArguments("echo-stdin");
+
+		// Act
+		var result = await cmd.ExecuteBufferedAsync();
+
+		// Assert
+		await Assert.That(result.StandardOutput.Trim()).IsEqualTo("Hello World!");
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_and_pipe_the_stdin_from_a_sync_anonymous_source()
+	{
+		// Arrange
+		var source = PipeSource.Create(destination
+			=> destination.Write("Hello World!"u8.ToArray()));
+
+		var cmd = source |
+				  new Command(Testing.Fixture.Program.FilePath)
+					  .WithArguments("echo-stdin");
+
+		// Act
+		var result = await cmd.ExecuteBufferedAsync();
+
+		// Assert
+		await Assert.That(result.StandardOutput.Trim()).IsEqualTo("Hello World!");
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_and_pipe_the_stdin_from_a_stream()
+	{
+		// Arrange
+		using var source = new MemoryStream("Hello World!"u8.ToArray());
+
+		var cmd = source |
+				  new Command(Testing.Fixture.Program.FilePath)
+					  .WithArguments("echo-stdin");
+
+		// Act
+		var result = await cmd.ExecuteBufferedAsync();
+
+		// Assert
+		await Assert.That(result.StandardOutput.Trim()).IsEqualTo("Hello World!");
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_and_pipe_the_stdin_from_memory()
+	{
+		// Arrange
+		var data = new ReadOnlyMemory<byte>("Hello World!"u8.ToArray());
+
+		var cmd = data |
+				  new Command(Testing.Fixture.Program.FilePath)
+					  .WithArguments("echo-stdin");
+
+		// Act
+		var result = await cmd.ExecuteBufferedAsync();
+
+		// Assert
+		await Assert.That(result.StandardOutput.Trim()).IsEqualTo("Hello World!");
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_and_pipe_the_stdin_from_a_byte_array()
+	{
+		// Arrange
+		var data = "Hello World!"u8.ToArray();
+
+		var cmd = data |
+				  new Command(Testing.Fixture.Program.FilePath)
+					  .WithArguments("echo-stdin");
+
+		// Act
+		var result = await cmd.ExecuteBufferedAsync();
+
+		// Assert
+		await Assert.That(result.StandardOutput.Trim()).IsEqualTo("Hello World!");
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_and_pipe_the_stdin_from_a_string()
+	{
+		// Arrange
+		var data = "Hello World!";
+
+		var cmd = data |
+				  new Command(Testing.Fixture.Program.FilePath)
+					  .WithArguments("echo-stdin");
+
+		// Act
+		var result = await cmd.ExecuteBufferedAsync();
+
+		// Assert
+		await Assert.That(result.StandardOutput.Trim()).IsEqualTo("Hello World!");
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_and_pipe_the_stdin_from_another_command()
+	{
+		// Arrange
+		var cmd =
+			new Command(Testing.Fixture.Program.FilePath)
+				.WithArguments(["generate", "blob", "--length", "100000"]) |
+			new Command(Testing.Fixture.Program.FilePath)
+				.WithArguments("length");
+
+		// Act
+		var result = await cmd.ExecuteBufferedAsync();
+
+		// Assert
+		await Assert.That(result.StandardOutput.Trim()).IsEqualTo("100000");
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_and_pipe_the_stdin_from_a_chain_of_commands()
+	{
+		// Arrange
+		var cmd =
+			"Hello world" |
+			new Command(Testing.Fixture.Program.FilePath)
+				.WithArguments("echo-stdin") |
+			new Command(Testing.Fixture.Program.FilePath)
+				.WithArguments(["echo-stdin", "--length", "5"]) |
+			new Command(Testing.Fixture.Program.FilePath)
+				.WithArguments("length");
+
+		// Act
+		var result = await cmd.ExecuteBufferedAsync();
+
+		// Assert
+		await Assert.That(result.StandardOutput.Trim()).IsEqualTo("5");
+	}
+
+	#endregion
+
+	#region Stdout
+
+	[Test]
+	public async Task I_can_execute_a_command_and_pipe_the_stdout_into_an_async_anonymous_target()
+	{
+		// Arrange
+		using var stream = new MemoryStream();
+
+		var target = PipeTarget.Create(async (origin, cancellationToken) =>
+			// ReSharper disable once AccessToDisposedClosure
+			await origin.CopyToAsync(stream, cancellationToken)
+		);
+
+		var cmd =
+			new Command(Testing.Fixture.Program.FilePath)
+				.WithArguments(["generate", "blob", "--length", "100000"]) |
+			target;
+
+		// Act
+		await cmd.ExecuteAsync();
+
+		// Assert
+		await Assert.That(stream.Length).IsEqualTo(100_000);
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_and_pipe_the_stdout_into_a_sync_anonymous_target()
+	{
+		// Arrange
+		using var stream = new MemoryStream();
+
+		var target = PipeTarget.Create(origin =>
+			// ReSharper disable once AccessToDisposedClosure
+			origin.CopyTo(stream)
+		);
+
+		var cmd =
+			new Command(Testing.Fixture.Program.FilePath)
+				.WithArguments(["generate", "blob", "--length", "100000"]) |
+			target;
+
+		// Act
+		await cmd.ExecuteAsync();
+
+		// Assert
+		await Assert.That(stream.Length).IsEqualTo(100_000);
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_and_pipe_the_stdout_into_a_stream()
+	{
+		// Arrange
+		using var stream = new MemoryStream();
+
+		var cmd =
+			new Command(Testing.Fixture.Program.FilePath)
+				.WithArguments(["generate", "blob", "--length", "100000"]) |
+			stream;
+
+		// Act
+		await cmd.ExecuteAsync();
+
+		// Assert
+		await Assert.That(stream.Length).IsEqualTo(100_000);
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_and_pipe_the_stdout_into_a_string_builder()
+	{
+		// Arrange
+		var buffer = new StringBuilder();
+
+		var cmd =
+			new Command(Testing.Fixture.Program.FilePath)
+				.WithArguments(["echo", "Hello World!"]) |
+			buffer;
+
+		// Act
+		await cmd.ExecuteAsync();
+
+		// Assert
+		await Assert.That(buffer.ToString().Trim()).IsEqualTo("Hello World!");
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_and_pipe_the_stdout_into_an_async_delegate()
+	{
+		// Arrange
+		var stdOutLinesCount = 0;
+
+		async Task HandleStdOutAsync(string line)
+		{
+			await Task.Yield();
+			stdOutLinesCount++;
+		}
+
+		var cmd =
+			new Command(Testing.Fixture.Program.FilePath)
+				.WithArguments(["generate", "clob", "--lines", "100"]) |
+			HandleStdOutAsync;
+
+		// Act
+		await cmd.ExecuteAsync();
+
+		// Assert
+		await Assert.That(stdOutLinesCount).IsEqualTo(100);
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_and_pipe_the_stdout_into_an_async_delegate_with_cancellation()
+	{
+		// Arrange
+		var stdOutLinesCount = 0;
+
+		async Task HandleStdOutAsync(string line, CancellationToken cancellationToken = default)
+		{
+			await Task.Delay(1, cancellationToken);
+			stdOutLinesCount++;
+		}
+
+		var cmd =
+			new Command(Testing.Fixture.Program.FilePath)
+				.WithArguments(["generate", "clob", "--lines", "100"]) |
+			HandleStdOutAsync;
+
+		// Act
+		await cmd.ExecuteAsync();
+
+		// Assert
+		await Assert.That(stdOutLinesCount).IsEqualTo(100);
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_and_pipe_the_stdout_into_a_sync_delegate()
+	{
+		// Arrange
+		var stdOutLinesCount = 0;
+
+		void HandleStdOut(string line)
+		{
+			stdOutLinesCount++;
+		}
+
+		var cmd =
+			new Command(Testing.Fixture.Program.FilePath)
+				.WithArguments(["generate", "clob", "--lines", "100"]) |
+			HandleStdOut;
+
+		// Act
+		await cmd.ExecuteAsync();
+
+		// Assert
+		await Assert.That(stdOutLinesCount).IsEqualTo(100);
+	}
+
+	#endregion
+
+	#region Stdout & Stderr
+
+	[Test]
+	public async Task I_can_execute_a_command_and_pipe_the_stdout_and_stderr_into_separate_stream()
+	{
+		// Arrange
+		using var stdOut = new MemoryStream();
+		using var stdErr = new MemoryStream();
+
+		var cmd =
+			new Command(Testing.Fixture.Program.FilePath)
+				.WithArguments(["generate", "blob", "--target", "all", "--length", "100000"]) |
+			(stdOut, stdErr);
+
+		// Act
+		await cmd.ExecuteAsync();
+
+		// Assert
+		using (Assert.Multiple())
+		{
+			await Assert.That(stdOut.Length).IsEqualTo(100_000);
+			await Assert.That(stdErr.Length).IsEqualTo(100_000);
+		}
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_and_pipe_the_stdout_and_stderr_into_string_builder()
+	{
+		// Arrange
+		var stdOutBuffer = new StringBuilder();
+		var stdErrBuffer = new StringBuilder();
+
+		var cmd =
+			new Command(Testing.Fixture.Program.FilePath)
+				.WithArguments(["echo", "Hello world!", "--target", "all"]) |
+			(stdOutBuffer, stdErrBuffer);
+
+		// Act
+		await cmd.ExecuteAsync();
+
+		// Assert
+		using (Assert.Multiple())
+		{
+			await Assert.That(stdOutBuffer.ToString().Trim()).IsEqualTo("Hello world!");
+			await Assert.That(stdErrBuffer.ToString().Trim()).IsEqualTo("Hello world!");
+		}
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_and_pipe_the_stdout_and_stderr_into_separate_async_delegate()
+	{
+		// Arrange
+		var stdOutLinesCount = 0;
+		var stdErrLinesCount = 0;
+
+		async Task HandleStdOutAsync(string line)
+		{
+			await Task.Yield();
+			stdOutLinesCount++;
+		}
+
+		async Task HandleStdErrAsync(string line)
+		{
+			await Task.Yield();
+			stdErrLinesCount++;
+		}
+
+		var cmd =
+			new Command(Testing.Fixture.Program.FilePath)
+				.WithArguments(["generate", "clob", "--target", "all", "--lines", "100"]) |
+			(HandleStdOutAsync, HandleStdErrAsync);
+
+		// Act
+		await cmd.ExecuteAsync();
+
+		// Assert
+		using (Assert.Multiple())
+		{
+			await Assert.That(stdOutLinesCount).IsEqualTo(100);
+			await Assert.That(stdErrLinesCount).IsEqualTo(100);
+		}
+	}
+
+	[Test]
+	public async Task
+		I_can_execute_a_command_and_pipe_the_stdout_and_stderr_into_separate_async_delegate_with_cancellation()
+	{
+		// Arrange
+		var stdOutLinesCount = 0;
+		var stdErrLinesCount = 0;
+
+		async Task HandleStdOutAsync(string line, CancellationToken cancellationToken = default)
+		{
+			await Task.Delay(1, cancellationToken);
+			stdOutLinesCount++;
+		}
+
+		async Task HandleStdErrAsync(string line, CancellationToken cancellationToken = default)
+		{
+			await Task.Delay(1, cancellationToken);
+			stdErrLinesCount++;
+		}
+
+		var cmd =
+			new Command(Testing.Fixture.Program.FilePath)
+				.WithArguments(["generate", "clob", "--target", "all", "--lines", "100"]) |
+			(HandleStdOutAsync, HandleStdErrAsync);
+
+		// Act
+		await cmd.ExecuteAsync();
+
+		// Assert
+		using (Assert.Multiple())
+		{
+			await Assert.That(stdOutLinesCount).IsEqualTo(100);
+			await Assert.That(stdErrLinesCount).IsEqualTo(100);
+		}
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_and_pipe_the_stdout_and_stderr_into_separate_sync_delegate()
+	{
+		// Arrange
+		var stdOutLinesCount = 0;
+		var stdErrLinesCount = 0;
+
+		void HandleStdOut(string line)
+		{
+			stdOutLinesCount++;
+		}
+
+		void HandleStdErr(string line)
+		{
+			stdErrLinesCount++;
+		}
+
+		var cmd =
+			new Command(Testing.Fixture.Program.FilePath)
+				.WithArguments(["generate", "clob", "--target", "all", "--lines", "100"]) |
+			(HandleStdOut, HandleStdErr);
+
+		// Act
+		await cmd.ExecuteAsync();
+
+		// Assert
+		using (Assert.Multiple())
+		{
+			await Assert.That(stdOutLinesCount).IsEqualTo(100);
+			await Assert.That(stdErrLinesCount).IsEqualTo(100);
+		}
+	}
+
+	#endregion
+
+	[Test]
+	public async Task I_can_execute_a_command_and_pipe_the_stdout_into_multiple_targets()
+	{
+		// Arrange
+		using var stream1 = new MemoryStream();
+		using var stream2 = new MemoryStream();
+		using var stream3 = new MemoryStream();
+
+		var target = PipeTarget.Merge(
+			PipeTarget.ToStream(stream1),
+			PipeTarget.ToStream(stream2),
+			PipeTarget.ToStream(stream3)
+		);
+
+		var cmd = new Command(Testing.Fixture.Program.FilePath)
+					  .WithArguments(["generate", "blob", "--length", "100000"]) |
+				  target;
+
+		// Act
+		await cmd.ExecuteAsync();
+
+		// Assert
+		using (Assert.Multiple())
+		{
+			await Assert.That(stream1.Length).IsEqualTo(100_000);
+			await Assert.That(stream2.Length).IsEqualTo(100_000);
+			await Assert.That(stream3.Length).IsEqualTo(100_000);
+			await Assert.That(stream1.ToArray()).IsEquivalentTo(stream2.ToArray());
+			await Assert.That(stream2.ToArray()).IsEquivalentTo(stream3.ToArray());
+		}
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_and_pipe_the_stdout_into_multiple_hierarchical_targets()
+	{
+		// Arrange
+		using var stream1 = new MemoryStream();
+		using var stream2 = new MemoryStream();
+		using var stream3 = new MemoryStream();
+		using var stream4 = new MemoryStream();
+
+		var target = PipeTarget.Merge(
+			PipeTarget.ToStream(stream1),
+			PipeTarget.Merge(
+				PipeTarget.ToStream(stream2),
+				PipeTarget.Merge(
+					PipeTarget.ToStream(stream3),
+					PipeTarget.ToStream(stream4))));
+
+		var cmd = new Command(Testing.Fixture.Program.FilePath)
+					  .WithArguments(["generate", "blob", "--length", "100000"]) |
+				  target;
+
+		// Act
+		await cmd.ExecuteAsync();
+
+		// Assert
+		using (Assert.Multiple())
+		{
+			await Assert.That(stream1.Length).IsEqualTo(100_000);
+			await Assert.That(stream2.Length).IsEqualTo(100_000);
+			await Assert.That(stream3.Length).IsEqualTo(100_000);
+			await Assert.That(stream4.Length).IsEqualTo(100_000);
+			await Assert.That(stream1.ToArray()).IsEquivalentTo(stream2.ToArray());
+			await Assert.That(stream2.ToArray()).IsEquivalentTo(stream3.ToArray());
+			await Assert.That(stream3.ToArray()).IsEquivalentTo(stream4.ToArray());
+		}
+	}
+}

src/process.tests/ValidationTests.cs

@@ -0,0 +1,58 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using Geekeey.Process.Buffered;
+
+namespace Geekeey.Process.Tests;
+
+internal sealed class ValidationTests
+{
+	private static Command Exit()
+	{
+		return new Command(Testing.Fixture.Program.FilePath)
+			.WithArguments(["exit", "1"]);
+	}
+
+	[Test]
+	public async Task I_can_try_to_execute_a_command_and_get_an_error_if_it_returns_a_non_zero_exit_code()
+	{
+		// Arrange
+		var cmd = Exit();
+
+		// Act & Assert
+		await Assert.That(async () => await cmd.ExecuteAsync()).Throws<CommandExecutionException>().And
+			.Member(static exception => exception.Message, static source => source.Contains("a non-zero exit code (1)")).And
+			.Member(static exception => exception.ExitCode, static source => source.IsEqualTo(1));
+	}
+
+	[Test]
+	public async Task I_can_try_to_execute_a_command_with_buffering_and_get_a_detailed_error_if_it_returns_a_non_zero_exit_code()
+	{
+		// Arrange
+		var cmd = Exit();
+
+
+		// Act & Assert
+		await Assert.That(async () => await cmd.ExecuteBufferedAsync()).Throws<CommandExecutionException>().And
+			.Member(static exception => exception.Message, static source => source.Contains("Exit code set to 1")).And
+			.Member(static exception => exception.ExitCode, static source => source.IsEqualTo(1));
+	}
+
+	[Test]
+	public async Task I_can_execute_a_command_without_validating_the_exit_code()
+	{
+		// Arrange
+		var cmd = Exit()
+			.WithExitValidation(ValidationMode.None);
+
+		// Act
+		var result = await cmd.ExecuteAsync();
+
+		// Assert
+		using (Assert.Multiple())
+		{
+			await Assert.That(result.ExitCode).IsEqualTo(1);
+			await Assert.That(result.IsSuccess).IsFalse();
+		}
+	}
+}

src/process.tests/_fixture/PlatformAttribute.cs

@@ -0,0 +1,35 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+namespace Geekeey.Process.Tests;
+
+internal sealed class PlatformAttribute : SkipAttribute
+{
+	// from the OperatingSystem definitions
+
+	public const string Browser = "BROWSER";
+	public const string Wasi = "WASI";
+	public const string Windows = "WINDOWS";
+	public const string Osx = "OSX";
+	public const string MacCatalyst = "MACCATALYST";
+	public const string Ios = "IOS";
+	public const string Tvos = "TVOS";
+	public const string Android = "ANDROID";
+	public const string Linux = "LINUX";
+	public const string Freebsd = "FREEBSD";
+	public const string Netbsd = "NETBSD";
+	public const string Illumos = "ILLUMOS";
+	public const string Solaris = "SOLARIS";
+
+	private readonly string[] _os;
+
+	public PlatformAttribute(params string[] os) : base("Test skipped on unsupported platform.")
+	{
+		_os = os;
+	}
+
+	public override Task<bool> ShouldSkip(TestRegisteredContext context)
+	{
+		return Task.FromResult(!_os.Any(OperatingSystem.IsOSPlatform));
+	}
+}

src/process.tests/_fixture/ProcessTree.cs

@@ -0,0 +1,21 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+namespace Geekeey.Process.Tests;
+
+internal static class ProcessTree
+{
+	public static bool HasExited(int id)
+	{
+		try
+		{
+			using var process = System.Diagnostics.Process.GetProcessById(id);
+			return process.HasExited;
+		}
+		catch
+		{
+			// GetProcessById throws if the process can not be found, which means it is not running!
+			return true;
+		}
+	}
+}

src/process.tests/_fixture/TestEnvironment.cs

@@ -0,0 +1,32 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+namespace Geekeey.Process.Tests;
+
+internal sealed class TestEnvironment : IDisposable
+{
+	private readonly Action _action;
+
+	private TestEnvironment(Action action)
+	{
+		_action = action;
+	}
+
+	public static TestEnvironment Create(string name, string? value)
+	{
+		var lastValue = Environment.GetEnvironmentVariable(name);
+		Environment.SetEnvironmentVariable(name, value);
+
+		return new TestEnvironment(() => Environment.SetEnvironmentVariable(name, lastValue));
+	}
+
+	public static TestEnvironment ExtendPath(string path)
+	{
+		return Create("PATH", Environment.GetEnvironmentVariable("PATH") + Path.PathSeparator + path);
+	}
+
+	public void Dispose()
+	{
+		_action();
+	}
+}

src/process.tests/_fixture/TestTempDirectory.cs

@@ -0,0 +1,34 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+namespace Geekeey.Process.Tests;
+
+internal sealed class TestTempDirectory : IDisposable
+{
+	private TestTempDirectory(string path)
+	{
+		Path = path;
+	}
+
+	public static TestTempDirectory Create()
+	{
+		var location = System.Reflection.Assembly.GetExecutingAssembly().Location;
+		var pwd = System.IO.Path.GetDirectoryName(location) ?? Directory.GetCurrentDirectory();
+		var dirPath = System.IO.Path.Combine(pwd, "Temp", Guid.NewGuid().ToString());
+
+		Directory.CreateDirectory(dirPath);
+
+		return new TestTempDirectory(dirPath);
+	}
+
+	public string Path { get; }
+
+	public void Dispose()
+	{
+		try
+		{
+			Directory.Delete(Path, recursive: true);
+		}
+		catch (DirectoryNotFoundException) { }
+	}
+}

src/process/ArgumentsBuilder.cs

@@ -0,0 +1,153 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using System.Globalization;
+using System.Text;
+
+namespace Geekeey.Process;
+
+/// <summary>
+/// Builder that helps format command-line arguments into a string.
+/// </summary>
+public sealed partial class ArgumentsBuilder
+{
+	private static readonly IFormatProvider DefaultFormatProvider = CultureInfo.InvariantCulture;
+
+	private readonly StringBuilder _buffer = new();
+
+	/// <summary>
+	/// Adds the specified value to the list of arguments.
+	/// </summary>
+	public ArgumentsBuilder Add(string value, bool escape = true)
+	{
+		if (_buffer.Length > 0)
+		{
+			_buffer.Append(' ');
+		}
+
+		_buffer.Append(escape ? Escape(value) : value);
+
+		return this;
+	}
+
+	/// <summary>
+	/// Adds the specified values to the list of arguments.
+	/// </summary>
+	public ArgumentsBuilder Add(IEnumerable<string> values, bool escape = true)
+	{
+		foreach (var value in values)
+		{
+			Add(value, escape);
+		}
+
+		return this;
+	}
+
+	/// <summary>
+	/// Adds the specified value to the list of arguments.
+	/// </summary>
+	public ArgumentsBuilder Add(IFormattable value, IFormatProvider formatProvider, bool escape = true)
+	{
+		return Add(value.ToString(null, formatProvider), escape);
+	}
+
+	/// <summary>
+	/// Adds the specified value to the list of arguments.
+	/// The value is converted to string using invariant culture.
+	/// </summary>
+	public ArgumentsBuilder Add(IFormattable value, bool escape = true)
+	{
+		return Add(value, DefaultFormatProvider, escape);
+	}
+
+	/// <summary>
+	/// Adds the specified values to the list of arguments.
+	/// </summary>
+	public ArgumentsBuilder Add(IEnumerable<IFormattable> values, IFormatProvider formatProvider, bool escape = true)
+	{
+		foreach (var value in values)
+		{
+			Add(value, formatProvider, escape);
+		}
+
+		return this;
+	}
+
+	/// <summary>
+	/// Adds the specified values to the list of arguments.
+	/// The values are converted to string using invariant culture.
+	/// </summary>
+	public ArgumentsBuilder Add(IEnumerable<IFormattable> values, bool escape = true)
+	{
+		return Add(values, DefaultFormatProvider, escape);
+	}
+
+	/// <summary>
+	/// Builds the resulting arguments string.
+	/// </summary>
+	public string Build()
+	{
+		return _buffer.ToString();
+	}
+}
+
+public partial class ArgumentsBuilder
+{
+	private static string Escape(string argument)
+	{
+		// Short circuit if the argument is clean and doesn't need escaping
+		if (argument.Length > 0 && argument.All(c => !char.IsWhiteSpace(c) && c is not '"'))
+		{
+			return argument;
+		}
+
+		var buffer = new StringBuilder();
+
+		buffer.Append('"');
+
+		for (var i = 0; i < argument.Length;)
+		{
+			var c = argument[i++];
+
+			switch (c)
+			{
+				case '\\':
+					{
+						var backslashCount = 1;
+						while (i < argument.Length && argument[i] == '\\')
+						{
+							backslashCount++;
+							i++;
+						}
+
+						if (i == argument.Length)
+						{
+							buffer.Append('\\', backslashCount * 2);
+						}
+						else if (argument[i] == '"')
+						{
+							buffer.Append('\\', (backslashCount * 2) + 1).Append('"');
+
+							i++;
+						}
+						else
+						{
+							buffer.Append('\\', backslashCount);
+						}
+
+						break;
+					}
+				case '"':
+					buffer.Append('\\').Append('"');
+					break;
+				default:
+					buffer.Append(c);
+					break;
+			}
+		}
+
+		buffer.Append('"');
+
+		return buffer.ToString();
+	}
+}

src/process/Buffered/BufferedCommandExtensions.cs

@@ -0,0 +1,91 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using System.Text;
+
+namespace Geekeey.Process.Buffered;
+
+/// <summary>
+/// Buffered execution model.
+/// </summary>
+public static class BufferedCommandExtensions
+{
+	/// <inheritdoc cref="BufferedCommandExtensions"/>
+	extension(Command command)
+	{
+		/// <summary>
+		/// Executes the command asynchronously with buffering.
+		/// Data written to the standard output and standard error streams is decoded as text
+		/// and returned as part of the result object.
+		/// </summary>
+		/// <remarks>
+		/// This method can be awaited.
+		/// </remarks>
+		public CommandTask<BufferedCommandResult> ExecuteBufferedAsync(Encoding standardOutputEncoding, Encoding standardErrorEncoding,
+			CancellationToken cancellationToken = default)
+		{
+			var stdOutBuffer = new StringBuilder();
+			var stdErrBuffer = new StringBuilder();
+
+			var stdOutPipe = PipeTarget.Merge(command.StandardOutputPipe,
+				PipeTarget.ToStringBuilder(stdOutBuffer, standardOutputEncoding));
+
+			var stdErrPipe = PipeTarget.Merge(command.StandardErrorPipe,
+				PipeTarget.ToStringBuilder(stdErrBuffer, standardErrorEncoding));
+
+			var commandWithPipes = command
+				.WithStandardOutputPipe(stdOutPipe)
+				.WithStandardErrorPipe(stdErrPipe);
+
+			return commandWithPipes
+				.ExecuteAsync(cancellationToken)
+				.Bind(async task =>
+				{
+					try
+					{
+						var result = await task;
+
+						return new BufferedCommandResult(result.ExitCode, result.StartTime, result.ExitTime,
+							stdOutBuffer.ToString(), stdErrBuffer.ToString());
+					}
+					catch (CommandExecutionException exception)
+					{
+						var message = $"""
+									   Command execution failed, see the inner exception for details.
+									   Standard error:
+									   {stdErrBuffer.ToString().Trim()}
+									   """;
+						throw new CommandExecutionException(exception.Command, exception.ExitCode, message, exception);
+					}
+				});
+		}
+
+		/// <summary>
+		/// Executes the command asynchronously with buffering.
+		/// Data written to the standard output and standard error streams is decoded as text
+		/// and returned as part of the result object.
+		/// </summary>
+		/// <remarks>
+		/// This method can be awaited.
+		/// </remarks>
+		public CommandTask<BufferedCommandResult> ExecuteBufferedAsync(Encoding encoding,
+			CancellationToken cancellationToken = default)
+		{
+			return command.ExecuteBufferedAsync(encoding, encoding, cancellationToken);
+		}
+
+		/// <summary>
+		/// Executes the command asynchronously with buffering.
+		/// Data written to the standard output and standard error streams is decoded as text
+		/// and returned as part of the result object.
+		/// Uses <see cref="Console.OutputEncoding" /> for decoding.
+		/// </summary>
+		/// <remarks>
+		/// This method can be awaited.
+		/// </remarks>
+		public CommandTask<BufferedCommandResult> ExecuteBufferedAsync(CancellationToken cancellationToken = default)
+		{
+			return command.ExecuteBufferedAsync(Console.OutputEncoding, cancellationToken);
+		}
+	}
+}

src/process/Buffered/BufferedCommandResult.cs

@@ -0,0 +1,51 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+namespace Geekeey.Process.Buffered;
+
+/// <summary>
+/// Result of a command execution, with buffered text data from standard output and standard error streams.
+/// </summary>
+public partial class BufferedCommandResult : CommandResult
+{
+	/// <summary>
+	/// Result of a command execution, with buffered text data from standard output and standard error streams.
+	/// </summary>
+	public BufferedCommandResult(int exitCode, DateTimeOffset startTime, DateTimeOffset exitTime, string standardOutput, string standardError)
+		: base(exitCode, startTime, exitTime)
+	{
+		StandardOutput = standardOutput;
+		StandardError = standardError;
+	}
+
+	/// <summary>
+	/// Standard output data produced by the underlying process.
+	/// </summary>
+	public string StandardOutput { get; }
+
+	/// <summary>
+	/// Standard error data produced by the underlying process.
+	/// </summary>
+	public string StandardError { get; }
+
+	/// <summary>
+	/// Deconstructs the result into its most important components.
+	/// </summary>
+	public void Deconstruct(out int exitCode, out string standardOutput, out string standardError)
+	{
+		exitCode = ExitCode;
+		standardOutput = StandardOutput;
+		standardError = StandardError;
+	}
+}
+
+public partial class BufferedCommandResult
+{
+	/// <summary>
+	/// Converts the result to a string value that corresponds to the <see cref="StandardOutput" /> property.
+	/// </summary>
+	public static implicit operator string(BufferedCommandResult result)
+	{
+		return result.StandardOutput;
+	}
+}

src/process/Command.Builder.cs

@@ -0,0 +1,129 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using System.Diagnostics.Contracts;
+
+namespace Geekeey.Process;
+
+public sealed partial class Command
+{
+	/// <summary>
+	/// Creates a copy of this command, setting the target file path to the specified value.
+	/// </summary>
+	[Pure]
+	public Command WithTargetFile(string targetFilePath)
+	{
+		return new Command(targetFilePath, Arguments, WorkingDirPath, Environment, Validation,
+			StandardInputPipe, StandardOutputPipe, StandardErrorPipe);
+	}
+
+	/// <summary>
+	/// Creates a copy of this command, setting the arguments to the specified value.
+	/// </summary>
+	/// <remarks>
+	/// Avoid using this overload, as it requires the arguments to be escaped manually.
+	/// Formatting errors may lead to unexpected bugs and security vulnerabilities.
+	/// </remarks>
+	[Pure]
+	public Command WithArguments(string arguments)
+	{
+		return new Command(TargetFilePath, arguments, WorkingDirPath, Environment, Validation,
+			StandardInputPipe, StandardOutputPipe, StandardErrorPipe);
+	}
+
+	/// <summary>
+	/// Creates a copy of this command, setting the arguments to the value
+	/// obtained by formatting the specified enumeration.
+	/// </summary>
+	[Pure]
+	public Command WithArguments(IEnumerable<string> arguments, bool escape = true)
+	{
+		return WithArguments(args => args.Add(arguments, escape));
+	}
+
+	/// <summary>
+	/// Creates a copy of this command, setting the arguments to the value
+	/// configured by the specified delegate.
+	/// </summary>
+	[Pure]
+	public Command WithArguments(Action<ArgumentsBuilder> configure)
+	{
+		var builder = new ArgumentsBuilder();
+		configure(builder);
+
+		return WithArguments(builder.Build());
+	}
+
+	/// <summary>
+	/// Creates a copy of this command, setting the working directory path to the specified value.
+	/// </summary>
+	[Pure]
+	public Command WithWorkingDirectory(string workingDirPath)
+	{
+		return new Command(TargetFilePath, Arguments, workingDirPath, Environment, Validation,
+			StandardInputPipe, StandardOutputPipe, StandardErrorPipe);
+	}
+
+	/// <summary>
+	/// Creates a copy of this command, setting the environment variables to the specified value.
+	/// </summary>
+	[Pure]
+	public Command WithEnvironment(IReadOnlyDictionary<string, string?> environmentVariables)
+	{
+		return new Command(TargetFilePath, Arguments, WorkingDirPath, environmentVariables, Validation,
+			StandardInputPipe, StandardOutputPipe, StandardErrorPipe);
+	}
+
+	/// <summary>
+	/// Creates a copy of this command, setting the environment variables to the value
+	/// configured by the specified delegate.
+	/// </summary>
+	[Pure]
+	public Command WithEnvironment(Action<EnvironmentVariablesBuilder> configure)
+	{
+		var builder = new EnvironmentVariablesBuilder();
+		configure(builder);
+
+		return WithEnvironment(builder.Build());
+	}
+
+	/// <summary>
+	/// Creates a copy of this command, setting the ExitMode options to the specified value.
+	/// </summary>
+	[Pure]
+	public Command WithExitValidation(ValidationMode validationMode)
+	{
+		return new Command(TargetFilePath, Arguments, WorkingDirPath, Environment, validationMode,
+			StandardInputPipe, StandardOutputPipe, StandardErrorPipe);
+	}
+
+	/// <summary>
+	/// Creates a copy of this command, setting the standard input pipe to the specified source.
+	/// </summary>
+	[Pure]
+	public Command WithStandardInputPipe(PipeSource source)
+	{
+		return new Command(TargetFilePath, Arguments, WorkingDirPath, Environment, Validation,
+			source, StandardOutputPipe, StandardErrorPipe);
+	}
+
+	/// <summary>
+	/// Creates a copy of this command, setting the standard output pipe to the specified target.
+	/// </summary>
+	[Pure]
+	public Command WithStandardOutputPipe(PipeTarget target)
+	{
+		return new Command(TargetFilePath, Arguments, WorkingDirPath, Environment, Validation,
+			StandardInputPipe, target, StandardErrorPipe);
+	}
+
+	/// <summary>
+	/// Creates a copy of this command, setting the standard error pipe to the specified target.
+	/// </summary>
+	[Pure]
+	public Command WithStandardErrorPipe(PipeTarget target)
+	{
+		return new Command(TargetFilePath, Arguments, WorkingDirPath, Environment, Validation,
+			StandardInputPipe, StandardOutputPipe, target);
+	}
+}

src/process/Command.Execute.cs

@@ -0,0 +1,231 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+namespace Geekeey.Process;
+
+public sealed partial class Command
+{
+	private static readonly Lazy<string?> ProcessPathLazy = new(() =>
+	{
+		using var process = System.Diagnostics.Process.GetCurrentProcess();
+		return process.MainModule?.FileName;
+	});
+
+	private static readonly TimeSpan CancelWaitTimeout = TimeSpan.FromSeconds(5);
+
+	private static string? ProcessPath => ProcessPathLazy.Value;
+
+	/// <summary>
+	/// Executes the command asynchronously.
+	/// </summary>
+	/// <remarks>
+	/// This method can be awaited.
+	/// </remarks>
+	/// <exception cref="InvalidOperationException">The command failed to start.</exception>
+	/// <exception cref="CommandExecutionException">The executed command exits and the <see cref="Validation"/> was not met.</exception>
+	/// <exception cref="OperationCanceledException">The <paramref name="cancellationToken"/> was canceled and the process was killed.</exception>
+	public CommandTask<CommandResult> ExecuteAsync(CancellationToken cancellationToken = default)
+	{
+		var process = new Process
+		{
+			FileName = GetOptimallyQualifiedTargetFilePath(), //
+			Arguments = Arguments,
+			WorkingDirectory = WorkingDirPath,
+		};
+
+		foreach (var (key, value) in Environment)
+		{
+			if (value is not null)
+			{
+				process.Environment[key] = value;
+			}
+			else
+			{
+				// Null value means we should remove the variable
+				process.Environment.Remove(key);
+			}
+		}
+
+		if (!process.Start(out var exception))
+		{
+			var message = $"Failed to start a process with file path '{process.FileName}'. " +
+						  $"Target file is not an executable or lacks execute permissions.";
+			throw new InvalidOperationException(message, exception);
+		}
+
+		// Extract the process ID before calling ExecuteAsync(), because the process may already be disposed by then.
+		var processId = process.Id;
+
+		var task = ExecuteAsync(process, cancellationToken);
+		return new CommandTask<CommandResult>(task, process, processId);
+
+		string GetOptimallyQualifiedTargetFilePath()
+		{
+			// Currently, we only need this workaround for script files on Windows, so short-circuit
+			// if we are on a different platform.
+			if (!OperatingSystem.IsWindows())
+			{
+				return TargetFilePath;
+			}
+
+			// Don't do anything for fully qualified paths or paths that already have an extension specified.
+			// System.Diagnostics.Process knows how to handle those without our help.
+			if (Path.IsPathFullyQualified(TargetFilePath) || !string.IsNullOrWhiteSpace(Path.GetExtension(TargetFilePath)))
+			{
+				return TargetFilePath;
+			}
+
+			return (
+					   from probeDirPath in GetProbeDirectoryPaths()
+					   where Directory.Exists(probeDirPath)
+					   select Path.Combine(probeDirPath, TargetFilePath)
+					   into baseFilePath
+					   from extension in GetPathExtensions()
+					   select Path.ChangeExtension(baseFilePath, extension)
+				   ).FirstOrDefault(File.Exists) ??
+				   TargetFilePath;
+
+			static IEnumerable<string> GetProbeDirectoryPaths()
+			{
+				// Executable directory
+				if (!string.IsNullOrWhiteSpace(ProcessPath))
+				{
+					var processDirPath = Path.GetDirectoryName(ProcessPath);
+
+					if (!string.IsNullOrWhiteSpace(processDirPath))
+					{
+						yield return processDirPath;
+					}
+				}
+
+				// Working directory
+				yield return Directory.GetCurrentDirectory();
+
+				// Directories on the PATH
+				if (System.Environment.GetEnvironmentVariable("PATH")?.Split(Path.PathSeparator) is { } paths)
+				{
+					foreach (var path in paths)
+					{
+						yield return path;
+					}
+				}
+			}
+
+			static IEnumerable<string> GetPathExtensions()
+			{
+				if (System.Environment.GetEnvironmentVariable("PATHEXT")?.Split(Path.PathSeparator) is { } extensions)
+				{
+					foreach (var extension in extensions)
+					{
+						yield return extension;
+					}
+				}
+				else
+				{
+					yield return ".COM";
+					yield return ".EXE";
+					yield return ".BAT";
+					yield return ".CMD";
+				}
+			}
+		}
+	}
+
+	private async Task<CommandResult> ExecuteAsync(Process process, CancellationToken cancellationToken = default)
+	{
+		using var _ = process;
+
+		// timeout is triggered when the cancel timeout expires after we tried to stop the process
+		// -> release wait for exit and pumping tasks after that timeout
+		using var timeout = new CancellationTokenSource();
+
+		var stdout = PipeStdOutAsync(process, timeout.Token);
+		var stderr = PipeStdErrAsync(process, timeout.Token);
+
+		var stdin = PipeStdInAsync(process, timeout.Token);
+
+		var pump = Task.WhenAll(stdout, stderr, stdin);
+
+		await using var registration = cancellationToken.Register(Stop, (process, timeout));
+
+		// wait for the process to exit or cancellation to be requested when cancellation is requested,
+		// we try to stop the process and then wait for it to exit with a timeout.
+		// When the timeout expires, we cancel the pumping tasks as well as the wait for the process exit.
+
+		try
+		{
+			await process.WaitForExitAsync(CancellationToken.None).WaitAsync(timeout.Token);
+		}
+		catch (OperationCanceledException)
+		{
+		}
+
+		// we still wait for the pumping to complete but ignore cancellation here
+		try
+		{
+			await pump;
+		}
+		catch (OperationCanceledException)
+		{
+		}
+
+		// if cancellation was requested, throw after the process was tried to stop
+		cancellationToken.ThrowIfCancellationRequested();
+
+		if (process.ExitCode is 0 || !Validation.HasFlag(ValidationMode.ZeroExitCode))
+		{
+			return new CommandResult(process.ExitCode, process.StartTime, process.ExitTime);
+		}
+
+		var message = $"Command execution failed because the underlying process ({process.FileName}#{process.Id}) " +
+					  $"returned a non-zero exit code ({process.ExitCode}).";
+		throw new CommandExecutionException(this, process.ExitCode, message);
+
+		static void Stop(object? state)
+		{
+			if (state is (Process process, CancellationTokenSource timeout))
+			{
+				timeout.CancelAfter(CancelWaitTimeout);
+				process.Kill();
+			}
+		}
+	}
+
+	private async Task PipeStdOutAsync(Process process, CancellationToken cancellationToken = default)
+	{
+		await using (process.StandardOutput)
+		{
+			await StandardOutputPipe.CopyFromAsync(process.StandardOutput, cancellationToken);
+		}
+	}
+
+	private async Task PipeStdErrAsync(Process process, CancellationToken cancellationToken = default)
+	{
+		await using (process.StandardError)
+		{
+			await StandardErrorPipe.CopyFromAsync(process.StandardError, cancellationToken);
+		}
+	}
+
+	private async Task PipeStdInAsync(Process process, CancellationToken cancellationToken = default)
+	{
+		await using (process.StandardInput)
+		{
+			try
+			{
+				// Some streams do not support cancellation, so we add a fallback that drops the task and returns early.
+				// This is important with stdin because the process might finish before the pipe has been fully
+				// exhausted, and we don't want to wait for it.
+				await StandardInputPipe.CopyToAsync(process.StandardInput, cancellationToken).WaitAsync(cancellationToken);
+			}
+			// Expect IOException: "The pipe has been ended" (Windows) or "Broken pipe" (Unix). This may happen if the
+			// process is terminated before the pipe has been exhausted. It's not an exceptional situation because the
+			// process may not need the entire stdin to complete successfully. We also can't rely on process.HasExited
+			// here because of potential race conditions.
+			catch (IOException ex) when (ex.GetType() == typeof(IOException))
+			{
+				// Don't catch derived exceptions, such as FileNotFoundException, to avoid false positives.
+			}
+		}
+	}
+}

src/process/Command.Piping.cs

@@ -0,0 +1,199 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using System.Diagnostics.Contracts;
+using System.Text;
+
+namespace Geekeey.Process;
+
+public sealed partial class Command
+{
+	/// <summary>
+	/// Creates a new command that pipes its standard output to the specified target.
+	/// </summary>
+	[Pure]
+	public static Command operator |(Command source, PipeTarget target)
+	{
+		return source.WithStandardOutputPipe(target);
+	}
+
+	/// <summary>
+	/// Creates a new command that pipes its standard output to the specified stream.
+	/// </summary>
+	[Pure]
+	public static Command operator |(Command source, Stream target)
+	{
+		return source | PipeTarget.ToStream(target);
+	}
+
+	/// <summary>
+	/// Creates a new command that pipes its standard output to the specified string builder.
+	/// Uses <see cref="Console.OutputEncoding" /> for decoding.
+	/// </summary>
+	[Pure]
+	public static Command operator |(Command source, StringBuilder target)
+	{
+		return source | PipeTarget.ToStringBuilder(target, Console.OutputEncoding);
+	}
+
+	/// <summary>
+	/// Creates a new command that pipes its standard output line-by-line to the specified
+	/// asynchronous delegate.
+	/// Uses <see cref="Console.OutputEncoding" /> for decoding.
+	/// </summary>
+	[Pure]
+	public static Command operator |(Command source, Func<string, CancellationToken, Task> target)
+	{
+		return source | PipeTarget.ToDelegate(target, Console.OutputEncoding);
+	}
+
+	/// <summary>
+	/// Creates a new command that pipes its standard output line-by-line to the specified
+	/// asynchronous delegate.
+	/// Uses <see cref="Console.OutputEncoding" /> for decoding.
+	/// </summary>
+	[Pure]
+	public static Command operator |(Command source, Func<string, Task> target)
+	{
+		return source | PipeTarget.ToDelegate(target, Console.OutputEncoding);
+	}
+
+	/// <summary>
+	/// Creates a new command that pipes its standard output line-by-line to the specified
+	/// synchronous delegate.
+	/// Uses <see cref="Console.OutputEncoding" /> for decoding.
+	/// </summary>
+	[Pure]
+	public static Command operator |(Command source, Action<string> target)
+	{
+		return source | PipeTarget.ToDelegate(target, Console.OutputEncoding);
+	}
+
+	/// <summary>
+	/// Creates a new command that pipes its standard output and standard error to the
+	/// specified targets.
+	/// </summary>
+	[Pure]
+	public static Command operator |(Command source, (PipeTarget stdOut, PipeTarget stdErr) targets)
+	{
+		return source.WithStandardOutputPipe(targets.stdOut).WithStandardErrorPipe(targets.stdErr);
+	}
+
+	/// <summary>
+	/// Creates a new command that pipes its standard output and standard error to the
+	/// specified streams.
+	/// </summary>
+	[Pure]
+	public static Command operator |(Command source, (Stream stdOut, Stream stdErr) targets)
+	{
+		return source | (PipeTarget.ToStream(targets.stdOut), PipeTarget.ToStream(targets.stdErr));
+	}
+
+	/// <summary>
+	/// Creates a new command that pipes its standard output and standard error to the
+	/// specified string builders.
+	/// Uses <see cref="Console.OutputEncoding" /> for decoding.
+	/// </summary>
+	[Pure]
+	public static Command operator |(Command source, (StringBuilder stdOut, StringBuilder stdErr) targets)
+	{
+		var stdout = PipeTarget.ToStringBuilder(targets.stdOut, Console.OutputEncoding);
+		var stderr = PipeTarget.ToStringBuilder(targets.stdErr, Console.OutputEncoding);
+		return source | (stdout, stderr);
+	}
+
+	/// <summary>
+	/// Creates a new command that pipes its standard output and standard error line-by-line
+	/// to the specified asynchronous delegates.
+	/// Uses <see cref="Console.OutputEncoding" /> for decoding.
+	/// </summary>
+	[Pure]
+	public static Command operator |(Command source, (Func<string, CancellationToken, Task> stdOut, Func<string, CancellationToken, Task> stdErr) targets)
+	{
+		var stdout = PipeTarget.ToDelegate(targets.stdOut, Console.OutputEncoding);
+		var stderr = PipeTarget.ToDelegate(targets.stdErr, Console.OutputEncoding);
+		return source | (stdout, stderr);
+	}
+
+	/// <summary>
+	/// Creates a new command that pipes its standard output and standard error line-by-line
+	/// to the specified asynchronous delegates.
+	/// Uses <see cref="Console.OutputEncoding" /> for decoding.
+	/// </summary>
+	[Pure]
+	public static Command operator |(Command source, (Func<string, Task> stdOut, Func<string, Task> stdErr) targets)
+	{
+		var stdout = PipeTarget.ToDelegate(targets.stdOut, Console.OutputEncoding);
+		var stderr = PipeTarget.ToDelegate(targets.stdErr, Console.OutputEncoding);
+		return source | (stdout, stderr);
+	}
+
+	/// <summary>
+	/// Creates a new command that pipes its standard output and standard error line-by-line
+	/// to the specified synchronous delegates.
+	/// Uses <see cref="Console.OutputEncoding" /> for decoding.
+	/// </summary>
+	[Pure]
+	public static Command operator |(Command source, (Action<string> stdOut, Action<string> stdErr) targets)
+	{
+		var stdout = PipeTarget.ToDelegate(targets.stdOut, Console.OutputEncoding);
+		var stderr = PipeTarget.ToDelegate(targets.stdErr, Console.OutputEncoding);
+		return source | (stdout, stderr);
+	}
+
+	/// <summary>
+	/// Creates a new command that pipes its standard input from the specified source.
+	/// </summary>
+	[Pure]
+	public static Command operator |(PipeSource source, Command target)
+	{
+		return target.WithStandardInputPipe(source);
+	}
+
+	/// <summary>
+	/// Creates a new command that pipes its standard input from the specified stream.
+	/// </summary>
+	[Pure]
+	public static Command operator |(Stream source, Command target)
+	{
+		return PipeSource.FromStream(source) | target;
+	}
+
+	/// <summary>
+	/// Creates a new command that pipes its standard input from the specified memory buffer.
+	/// </summary>
+	[Pure]
+	public static Command operator |(ReadOnlyMemory<byte> source, Command target)
+	{
+		return PipeSource.FromBytes(source) | target;
+	}
+
+	/// <summary>
+	/// Creates a new command that pipes its standard input from the specified byte array.
+	/// </summary>
+	[Pure]
+	public static Command operator |(byte[] source, Command target)
+	{
+		return PipeSource.FromBytes(source) | target;
+	}
+
+	/// <summary>
+	/// Creates a new command that pipes its standard input from the specified string.
+	/// Uses <see cref="Console.InputEncoding" /> for encoding.
+	/// </summary>
+	[Pure]
+	public static Command operator |(string source, Command target)
+	{
+		return PipeSource.FromString(source, Console.InputEncoding) | target;
+	}
+
+	/// <summary>
+	/// Creates a new command that pipes its standard input from the standard output of the
+	/// specified command.
+	/// </summary>
+	[Pure]
+	public static Command operator |(Command source, Command target)
+	{
+		return PipeSource.FromCommand(source) | target;
+	}
+}

src/process/Command.cs

@@ -0,0 +1,84 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using System.Diagnostics.CodeAnalysis;
+
+namespace Geekeey.Process;
+
+/// <summary>
+/// Instructions for running a process.
+/// </summary>
+public sealed partial class Command
+{
+	/// <summary>
+	/// Initializes an instance of <see cref="Command" />.
+	/// </summary>
+	public Command(string targetFilePath, string arguments, string workingDirPath,
+		IReadOnlyDictionary<string, string?> environment, ValidationMode validation,
+		PipeSource standardInputPipe, PipeTarget standardOutputPipe, PipeTarget standardErrorPipe)
+	{
+		TargetFilePath = targetFilePath;
+		Arguments = arguments;
+		WorkingDirPath = workingDirPath;
+		Environment = environment;
+		Validation = validation;
+		StandardInputPipe = standardInputPipe;
+		StandardOutputPipe = standardOutputPipe;
+		StandardErrorPipe = standardErrorPipe;
+	}
+
+	/// <summary>
+	/// Initializes an instance of <see cref="Command" />.
+	/// </summary>
+	public Command(string targetFilePath) : this(targetFilePath, string.Empty, Directory.GetCurrentDirectory(),
+		new Dictionary<string, string?>(), ValidationMode.ZeroExitCode, PipeSource.Null, PipeTarget.Null, PipeTarget.Null)
+	{
+	}
+
+	/// <summary>
+	/// File path of the executable, batch file, or script, that this command runs.
+	/// </summary>
+	public string TargetFilePath { get; }
+
+	/// <summary>
+	/// File path of the executable, batch file, or script, that this command runs.
+	/// </summary>
+	public string Arguments { get; }
+
+	/// <summary>
+	/// File path of the executable, batch file, or script, that this command runs.
+	/// </summary>
+	public string WorkingDirPath { get; }
+
+	/// <summary>
+	/// Environment variables set for the underlying process.
+	/// </summary>
+	public IReadOnlyDictionary<string, string?> Environment { get; }
+
+	/// <summary>
+	/// Strategy for validating the result of the execution.
+	/// </summary>
+	public ValidationMode Validation { get; }
+
+	/// <summary>
+	/// Pipe source for the standard input stream of the underlying process.
+	/// </summary>
+	public PipeSource StandardInputPipe { get; }
+
+	/// <summary>
+	/// Pipe target for the standard output stream of the underlying process.
+	/// </summary>
+	public PipeTarget StandardOutputPipe { get; }
+
+	/// <summary>
+	/// Pipe target for the standard error stream of the underlying process.
+	/// </summary>
+	public PipeTarget StandardErrorPipe { get; }
+
+	/// <inheritdoc />
+	[ExcludeFromCodeCoverage]
+	public override string ToString()
+	{
+		return $"{TargetFilePath} {Arguments}";
+	}
+}

src/process/CommandExecutionException.cs

@@ -0,0 +1,30 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+namespace Geekeey.Process;
+
+/// <summary>
+/// Exception thrown when the command fails to execute correctly.
+/// </summary>
+public class CommandExecutionException : Exception
+{
+	/// <summary>
+	/// Exception thrown when the command fails to execute correctly.
+	/// </summary>
+	public CommandExecutionException(Command command, int exitCode, string message, Exception? innerException = null)
+		: base(message, innerException)
+	{
+		Command = command;
+		ExitCode = exitCode;
+	}
+
+	/// <summary>
+	/// Command that triggered the exception.
+	/// </summary>
+	public Command Command { get; }
+
+	/// <summary>
+	/// Exit code returned by the process.
+	/// </summary>
+	public int ExitCode { get; }
+}

src/process/CommandResult.cs

@@ -0,0 +1,64 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+namespace Geekeey.Process;
+
+/// <summary>
+/// Represents the result of a command execution.
+/// </summary>
+public partial class CommandResult
+{
+	/// <summary>
+	/// Represents the result of a command execution.
+	/// </summary>
+	public CommandResult(int exitCode, DateTimeOffset startTime, DateTimeOffset exitTime)
+	{
+		ExitCode = exitCode;
+		StartTime = startTime;
+		ExitTime = exitTime;
+	}
+
+	/// <summary>
+	/// Exit code set by the underlying process.
+	/// </summary>
+	public int ExitCode { get; }
+
+	/// <summary>
+	/// Whether the command execution was successful (i.e. exit code is zero).
+	/// </summary>
+	public bool IsSuccess => ExitCode is 0;
+
+	/// <summary>
+	/// Time at which the command started executing.
+	/// </summary>
+	public DateTimeOffset StartTime { get; }
+
+	/// <summary>
+	/// Time at which the command finished executing.
+	/// </summary>
+	public DateTimeOffset ExitTime { get; }
+
+	/// <summary>
+	/// Total duration of the command execution.
+	/// </summary>
+	public TimeSpan RunTime => ExitTime - StartTime;
+}
+
+public partial class CommandResult
+{
+	/// <summary>
+	/// Converts the result to an integer value that corresponds to the <see cref="ExitCode" /> property.
+	/// </summary>
+	public static implicit operator int(CommandResult result)
+	{
+		return result.ExitCode;
+	}
+
+	/// <summary>
+	/// Converts the result to a boolean value that corresponds to the <see cref="IsSuccess" /> property.
+	/// </summary>
+	public static implicit operator bool(CommandResult result)
+	{
+		return result.IsSuccess;
+	}
+}

src/process/CommandTask.cs

@@ -0,0 +1,94 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using System.Runtime.CompilerServices;
+
+namespace Geekeey.Process;
+
+/// <summary>
+/// Represents an asynchronous execution of a command.
+/// </summary>
+public sealed partial class CommandTask<TResult> : IDisposable
+{
+	private readonly Process _process;
+
+	internal CommandTask(Task<TResult> task, Process process, int processId)
+	{
+		Task = task;
+		_process = process;
+		ProcessId = processId;
+	}
+
+	/// <summary>
+	/// Underlying task.
+	/// </summary>
+	public Task<TResult> Task { get; }
+
+	/// <summary>
+	/// Underlying process ID.
+	/// </summary>
+	public int ProcessId { get; }
+
+	internal CommandTask<T> Bind<T>(Func<Task<TResult>, Task<T>> transform)
+	{
+		return new CommandTask<T>(transform(Task), _process, ProcessId);
+	}
+
+	/// <summary>
+	/// Lazily maps the result of the task using the specified transform.
+	/// </summary>
+	internal CommandTask<T> Select<T>(Func<TResult, T> transform)
+	{
+		return Bind(async task => transform(await task));
+	}
+
+	/// <summary>
+	/// Signals the process with an interrupt request from the keyboard.
+	/// </summary>
+	public void Interrupt()
+	{
+		_process.Interrupt();
+	}
+
+	/// <summary>
+	/// Immediately stops the associated process and its descendent processes.
+	/// </summary>
+	public void Kill()
+	{
+		_process.Kill();
+	}
+
+	/// <summary>
+	/// Gets the awaiter of the underlying task.
+	/// Used to enable await expressions on this object.
+	/// </summary>
+	public TaskAwaiter<TResult> GetAwaiter()
+	{
+		return Task.GetAwaiter();
+	}
+
+	/// <summary>
+	/// Configures an awaiter used to await this task.
+	/// </summary>
+	public ConfiguredTaskAwaitable<TResult> ConfigureAwait(bool continueOnCapturedContext)
+	{
+		return Task.ConfigureAwait(continueOnCapturedContext);
+	}
+
+	/// <inheritdoc />
+	public void Dispose()
+	{
+		Task.Dispose();
+	}
+}
+
+public sealed partial class CommandTask<TResult>
+{
+	/// <summary>
+	/// Converts the command task into a regular task.
+	/// </summary>
+	public static implicit operator Task<TResult>(CommandTask<TResult> commandTask)
+	{
+		return commandTask.Task;
+	}
+}

src/process/EnvironmentVariablesBuilder.cs

@@ -0,0 +1,50 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+namespace Geekeey.Process;
+
+/// <summary>
+/// Builder that helps configure environment variables.
+/// </summary>
+public sealed class EnvironmentVariablesBuilder
+{
+	private readonly Dictionary<string, string?> _vars = new(StringComparer.Ordinal);
+
+	/// <summary>
+	/// Sets an environment variable with the specified name to the specified value.
+	/// </summary>
+	public EnvironmentVariablesBuilder Set(string name, string? value)
+	{
+		_vars[name] = value;
+		return this;
+	}
+
+	/// <summary>
+	/// Sets multiple environment variables from the specified sequence of key-value pairs.
+	/// </summary>
+	public EnvironmentVariablesBuilder Set(IEnumerable<KeyValuePair<string, string?>> variables)
+	{
+		foreach (var (name, value) in variables)
+		{
+			Set(name, value);
+		}
+
+		return this;
+	}
+
+	/// <summary>
+	/// Sets multiple environment variables from the specified dictionary.
+	/// </summary>
+	public EnvironmentVariablesBuilder Set(IReadOnlyDictionary<string, string?> variables)
+	{
+		return Set((IEnumerable<KeyValuePair<string, string?>>)variables);
+	}
+
+	/// <summary>
+	/// Builds the resulting environment variables.
+	/// </summary>
+	public IReadOnlyDictionary<string, string?> Build()
+	{
+		return new Dictionary<string, string?>(_vars, _vars.Comparer);
+	}
+}

src/process/Geekeey.Process.csproj

@@ -0,0 +1,32 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Library</OutputType>
+    <TargetFramework>net10.0</TargetFramework>
+    <IsPackable>true</IsPackable>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <GenerateDocumentationFile>true</GenerateDocumentationFile>
+    <!-- required because of native library import for libc -->
+    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+  </PropertyGroup>
+
+  <ItemGroup Condition="'$(Configuration)' == 'Debug'">
+    <InternalsVisibleTo Include="$(AssemblyName).Tests" />
+  </ItemGroup>
+
+  <PropertyGroup>
+    <PackageReadmeFile>package-readme.md</PackageReadmeFile>
+    <PackageIcon>package-icon.png</PackageIcon>
+    <PackageProjectUrl>https://code.geekeey.de/geekeey/process/src/branch/main/src/process</PackageProjectUrl>
+    <PackageLicenseExpression>EUPL-1.2</PackageLicenseExpression>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <None Include=".\package-icon.png" Pack="true" PackagePath="\" Visible="false" />
+    <None Include=".\package-readme.md" Pack="true" PackagePath="\" Visible="false" />
+    <None Include="..\..\LICENSE.md" Pack="true" PackagePath="\" Visible="false" />
+  </ItemGroup>
+
+</Project>

src/process/MemoryBufferStream.cs

@@ -0,0 +1,134 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using System.Buffers;
+using System.Diagnostics.CodeAnalysis;
+
+namespace Geekeey.Process;
+
+internal sealed class MemoryBufferStream : Stream
+{
+	public const int DefaultBufferSize = 81920;
+
+	private readonly SemaphoreSlim _writeLock = new(1, 1);
+	private readonly SemaphoreSlim _readLock = new(0, 1);
+
+	private IMemoryOwner<byte> _sharedBuffer = MemoryPool<byte>.Shared.Rent(DefaultBufferSize);
+	private int _sharedBufferBytes;
+	private int _sharedBufferBytesRead;
+
+	[ExcludeFromCodeCoverage] public override bool CanRead => true;
+
+	[ExcludeFromCodeCoverage] public override bool CanSeek => false;
+
+	[ExcludeFromCodeCoverage] public override bool CanWrite => true;
+
+	[ExcludeFromCodeCoverage] public override long Position { get; set; }
+
+	[ExcludeFromCodeCoverage] public override long Length => throw new NotSupportedException();
+
+	[ExcludeFromCodeCoverage]
+	public override void Write(byte[] buffer, int offset, int count)
+	{
+		WriteAsync(buffer, offset, count).GetAwaiter().GetResult();
+	}
+
+	[ExcludeFromCodeCoverage]
+	public override async Task WriteAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+	{
+		await WriteAsync(buffer.AsMemory(offset, count), cancellationToken);
+	}
+
+	public override async ValueTask WriteAsync(ReadOnlyMemory<byte> buffer, CancellationToken cancellationToken = default)
+	{
+		await _writeLock.WaitAsync(cancellationToken);
+
+		// Reset the buffer if the current one is too small for the incoming data
+		if (_sharedBuffer.Memory.Length < buffer.Length)
+		{
+			_sharedBuffer.Dispose();
+			_sharedBuffer = MemoryPool<byte>.Shared.Rent(buffer.Length);
+		}
+
+		buffer.CopyTo(_sharedBuffer.Memory);
+
+		_sharedBufferBytes = buffer.Length;
+		_sharedBufferBytesRead = 0;
+
+		_readLock.Release();
+	}
+
+	[ExcludeFromCodeCoverage]
+	public override int Read(byte[] buffer, int offset, int count)
+	{
+		return ReadAsync(buffer, offset, count).GetAwaiter().GetResult();
+	}
+
+	[ExcludeFromCodeCoverage]
+	public override async Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
+	{
+		return await ReadAsync(buffer.AsMemory(offset, count), cancellationToken);
+	}
+
+	public override async ValueTask<int> ReadAsync(Memory<byte> buffer, CancellationToken cancellationToken = default)
+	{
+		await _readLock.WaitAsync(cancellationToken);
+
+		var length = Math.Min(buffer.Length, _sharedBufferBytes - _sharedBufferBytesRead);
+
+		_sharedBuffer.Memory.Slice(_sharedBufferBytesRead, length).CopyTo(buffer);
+
+		_sharedBufferBytesRead += length;
+
+		// release the write lock if the consumer has finished reading all
+		// the previously written data.
+		if (_sharedBufferBytesRead >= _sharedBufferBytes)
+		{
+			_writeLock.Release();
+		}
+		// otherwise, release the read lock again so that the consumer can finish
+		// reading the data.
+		else
+		{
+			_readLock.Release();
+		}
+
+		return length;
+	}
+
+	public async Task ReportCompletionAsync(CancellationToken cancellationToken = default)
+	{
+		// write an empty buffer that will make ReadAsync(...) return 0, which signals the end of stream
+		await WriteAsync(Memory<byte>.Empty, cancellationToken);
+	}
+
+	protected override void Dispose(bool disposing)
+	{
+		if (disposing)
+		{
+			_readLock.Dispose();
+			_writeLock.Dispose();
+			_sharedBuffer.Dispose();
+		}
+
+		base.Dispose(disposing);
+	}
+
+	[ExcludeFromCodeCoverage]
+	public override void Flush()
+	{
+		throw new NotSupportedException();
+	}
+
+	[ExcludeFromCodeCoverage]
+	public override long Seek(long offset, SeekOrigin origin)
+	{
+		throw new NotSupportedException();
+	}
+
+	[ExcludeFromCodeCoverage]
+	public override void SetLength(long value)
+	{
+		throw new NotSupportedException();
+	}
+}

src/process/PipeSource.cs

@@ -0,0 +1,124 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using System.Text;
+
+namespace Geekeey.Process;
+
+/// <summary>
+/// Represents a pipe for the process's standard input stream.
+/// </summary>
+public abstract partial class PipeSource
+{
+	/// <summary>
+	/// Reads the binary content pushed into the pipe and writes it to the destination stream.
+	/// Destination stream represents the process's standard input stream.
+	/// </summary>
+	public abstract Task CopyToAsync(Stream destination, CancellationToken cancellationToken = default);
+}
+
+public partial class PipeSource
+{
+	private sealed class AnonymousPipeSource(Func<Stream, CancellationToken, Task> func) : PipeSource
+	{
+		public override async Task CopyToAsync(Stream destination, CancellationToken cancellationToken = default)
+		{
+			await func(destination, cancellationToken);
+		}
+	}
+}
+
+public abstract partial class PipeSource
+{
+	/// <summary>
+	/// Pipe source that does not provide any data.
+	/// Functionally equivalent to a null device.
+	/// </summary>
+	public static PipeSource Null { get; } = Create((_, cancellationToken)
+		=> !cancellationToken.IsCancellationRequested ? Task.CompletedTask : Task.FromCanceled(cancellationToken));
+
+	/// <summary>
+	/// Creates an anonymous pipe source with the <see cref="CopyToAsync(Stream, CancellationToken)" /> method
+	/// implemented by the specified asynchronous delegate.
+	/// </summary>
+	public static PipeSource Create(Func<Stream, CancellationToken, Task> func)
+	{
+		return new AnonymousPipeSource(func);
+	}
+
+	/// <summary>
+	/// Creates an anonymous pipe source with the <see cref="CopyToAsync(Stream, CancellationToken)" /> method
+	/// implemented by the specified synchronous delegate.
+	/// </summary>
+	public static PipeSource Create(Action<Stream> action)
+	{
+		return Create((destination, _) =>
+		{
+			action(destination);
+			return Task.CompletedTask;
+		});
+	}
+
+	/// <summary>
+	/// Creates a pipe source that reads from the specified stream.
+	/// </summary>
+	public static PipeSource FromStream(Stream stream)
+	{
+		return Create(stream.CopyToAsync);
+	}
+
+	/// <summary>
+	/// Creates a pipe source that reads from the specified file.
+	/// </summary>
+	public static PipeSource FromFile(string filePath)
+	{
+		return Create(async (destination, cancellationToken) =>
+		{
+			await using var source = File.OpenRead(filePath);
+			await source.CopyToAsync(destination, cancellationToken);
+		});
+	}
+
+	/// <summary>
+	/// Creates a pipe source that reads from the specified memory buffer.
+	/// </summary>
+	public static PipeSource FromBytes(ReadOnlyMemory<byte> data)
+	{
+		return Create(async (destination, cancellationToken) =>
+			await destination.WriteAsync(data, cancellationToken));
+	}
+
+	/// <summary>
+	/// Creates a pipe source that reads from the specified byte array.
+	/// </summary>
+	public static PipeSource FromBytes(byte[] data)
+	{
+		return FromBytes((ReadOnlyMemory<byte>)data);
+	}
+
+	/// <summary>
+	/// Creates a pipe source that reads from the specified string.
+	/// </summary>
+	public static PipeSource FromString(string str, Encoding encoding)
+	{
+		return FromBytes(encoding.GetBytes(str));
+	}
+
+	/// <summary>
+	/// Creates a pipe source that reads from the specified string.
+	/// Uses <see cref="Console.InputEncoding" /> for encoding.
+	/// </summary>
+	public static PipeSource FromString(string str)
+	{
+		return FromString(str, Console.InputEncoding);
+	}
+
+	/// <summary>
+	/// Creates a pipe source that reads from the standard output of the specified command.
+	/// </summary>
+	public static PipeSource FromCommand(Command command)
+	{
+		return Create(async (destination, cancellationToken) =>
+			await command.WithStandardOutputPipe(PipeTarget.ToStream(destination)).ExecuteAsync(cancellationToken));
+	}
+}

src/process/PipeTarget.cs

@@ -0,0 +1,314 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using System.Buffers;
+using System.Text;
+
+namespace Geekeey.Process;
+
+/// <summary>
+/// Represents a pipe for the process's standard output or standard error stream.
+/// </summary>
+public abstract partial class PipeTarget
+{
+	/// <summary>
+	/// Reads the binary content from the origin stream and pushes it into the pipe.
+	/// Origin stream represents the process's standard output or standard error stream.
+	/// </summary>
+	public abstract Task CopyFromAsync(Stream origin, CancellationToken cancellationToken = default);
+}
+
+public partial class PipeTarget
+{
+	private const int DefaultBufferSize = 1024;
+
+	private sealed class AnonymousPipeTarget(Func<Stream, CancellationToken, Task> func) : PipeTarget
+	{
+		public override async Task CopyFromAsync(Stream origin, CancellationToken cancellationToken = default)
+		{
+			await func(origin, cancellationToken);
+		}
+	}
+
+	private sealed class AggregatePipeTarget(IReadOnlyList<PipeTarget> targets) : PipeTarget
+	{
+		public IReadOnlyList<PipeTarget> Targets { get; } = targets;
+
+		public override async Task CopyFromAsync(Stream origin, CancellationToken cancellationToken = default)
+		{
+			using var cts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
+
+			// create a separate sub-stream for each target
+			var targetSubStreams = new Dictionary<PipeTarget, MemoryBufferStream>();
+			foreach (var target in Targets)
+			{
+				targetSubStreams[target] = new MemoryBufferStream();
+			}
+
+			try
+			{
+				// start piping in the background
+				async Task StartCopyAsync(KeyValuePair<PipeTarget, MemoryBufferStream> targetSubStream)
+				{
+					var (target, subStream) = targetSubStream;
+
+					try
+					{
+						// ReSharper disable once AccessToDisposedClosure
+						await target.CopyFromAsync(subStream, cts.Token);
+					}
+					catch
+					{
+						// abort the operation if any of the targets fail
+
+						// ReSharper disable once AccessToDisposedClosure
+						await cts.CancelAsync();
+
+						throw;
+					}
+				}
+
+				var readingTask = Task.WhenAll(targetSubStreams.Select(StartCopyAsync));
+
+				try
+				{
+					// read from the main stream and replicate the data to each sub-stream
+					using var buffer = MemoryPool<byte>.Shared.Rent(MemoryBufferStream.DefaultBufferSize);
+
+					while (true)
+					{
+						var bytesRead = await origin.ReadAsync(buffer.Memory, cts.Token);
+
+						if (bytesRead <= 0)
+						{
+							break;
+						}
+
+						foreach (var (_, subStream) in targetSubStreams)
+						{
+							await subStream.WriteAsync(buffer.Memory[..bytesRead], cts.Token);
+						}
+					}
+
+					// report that transmission is complete
+					foreach (var (_, subStream) in targetSubStreams)
+					{
+						await subStream.ReportCompletionAsync(cts.Token);
+					}
+				}
+				finally
+				{
+					// wait for all targets to finish and maybe propagate exceptions
+					await readingTask;
+				}
+			}
+			finally
+			{
+				foreach (var (_, stream) in targetSubStreams)
+				{
+					await stream.DisposeAsync();
+				}
+			}
+		}
+	}
+}
+
+public partial class PipeTarget
+{
+	/// <summary>
+	/// Pipe target that discards all data. Functionally equivalent to a null device.
+	/// </summary>
+	/// <remarks>
+	/// Using this target results in the corresponding stream (standard output or standard error) not being opened for
+	/// the underlying process at all. In the vast majority of cases, this behavior should be functionally equivalent to
+	/// piping to a null stream, but without the performance overhead of consuming and discarding unneeded data. This
+	/// may be undesirable in certain situations, in which case it's recommended to pipe to a null stream explicitly
+	/// using <see cref="ToStream(Stream)" /> with <see cref="Stream.Null" />.
+	/// </remarks>
+	public static PipeTarget Null { get; } = Create((_, cancellationToken) =>
+		!cancellationToken.IsCancellationRequested ? Task.CompletedTask : Task.FromCanceled(cancellationToken));
+
+	/// <summary>
+	/// Creates an anonymous pipe target with the <see cref="CopyFromAsync(Stream, CancellationToken)" /> method
+	/// implemented by the specified asynchronous delegate.
+	/// </summary>
+	public static PipeTarget Create(Func<Stream, CancellationToken, Task> func)
+	{
+		return new AnonymousPipeTarget(func);
+	}
+
+	/// <summary>
+	/// Creates an anonymous pipe target with the <see cref="CopyFromAsync(Stream, CancellationToken)" /> method
+	/// implemented by the specified synchronous delegate.
+	/// </summary>
+	public static PipeTarget Create(Action<Stream> action)
+	{
+		return Create((origin, _) =>
+		{
+			action(origin);
+			return Task.CompletedTask;
+		});
+	}
+
+	/// <summary>
+	/// Creates a pipe target that writes to the specified stream.
+	/// </summary>
+	public static PipeTarget ToStream(Stream stream)
+	{
+		return Create(async (origin, cancellationToken) =>
+			await origin.CopyToAsync(stream, cancellationToken));
+	}
+
+	/// <summary>
+	/// Creates a pipe target that writes to the specified file.
+	/// </summary>
+	public static PipeTarget ToFile(string filePath)
+	{
+		return Create(async (origin, cancellationToken) =>
+		{
+			await using var target = File.Create(filePath);
+			await origin.CopyToAsync(target, cancellationToken);
+		});
+	}
+
+	/// <summary>
+	/// Creates a pipe target that writes to the specified string builder.
+	/// </summary>
+	public static PipeTarget ToStringBuilder(StringBuilder stringBuilder, Encoding encoding)
+	{
+		return Create(async (origin, cancellationToken) =>
+		{
+			using var reader = new StreamReader(origin, encoding, false, DefaultBufferSize, true);
+			using var buffer = MemoryPool<char>.Shared.Rent(DefaultBufferSize);
+
+			while (!cancellationToken.IsCancellationRequested)
+			{
+				var charsRead = await reader.ReadAsync(buffer.Memory, cancellationToken);
+				if (charsRead <= 0)
+				{
+					break;
+				}
+
+				stringBuilder.Append(buffer.Memory[..charsRead]);
+			}
+		});
+	}
+
+	/// <summary>
+	/// Creates a pipe target that writes to the specified string builder.
+	/// Uses <see cref="Console.OutputEncoding" /> for decoding.
+	/// </summary>
+	public static PipeTarget ToStringBuilder(StringBuilder stringBuilder)
+	{
+		return ToStringBuilder(stringBuilder, Console.OutputEncoding);
+	}
+
+	/// <summary>
+	/// Creates a pipe target that invokes the specified asynchronous delegate on every line written to the stream.
+	/// </summary>
+	public static PipeTarget ToDelegate(Func<string, CancellationToken, Task> func, Encoding encoding)
+	{
+		return Create(async (origin, cancellationToken) =>
+		{
+			using var reader = new StreamReader(origin, encoding, false, DefaultBufferSize, true);
+			while (await reader.ReadLineAsync(cancellationToken) is { } line)
+			{
+				await func(line, cancellationToken);
+			}
+		});
+	}
+
+	/// <summary>
+	/// Creates a pipe target that invokes the specified asynchronous delegate on every line written to the stream.
+	/// Uses <see cref="Console.OutputEncoding" /> for decoding.
+	/// </summary>
+	public static PipeTarget ToDelegate(Func<string, CancellationToken, Task> func)
+	{
+		return ToDelegate(func, Console.OutputEncoding);
+	}
+
+	/// <summary>
+	/// Creates a pipe target that invokes the specified asynchronous delegate on every line written to the stream.
+	/// </summary>
+	public static PipeTarget ToDelegate(Func<string, Task> func, Encoding encoding)
+	{
+		return ToDelegate(async (line, _) => await func(line), encoding);
+	}
+
+	/// <summary>
+	/// Creates a pipe target that invokes the specified asynchronous delegate on every line written to the stream.
+	/// Uses <see cref="Console.OutputEncoding" /> for decoding.
+	/// </summary>
+	public static PipeTarget ToDelegate(Func<string, Task> func)
+	{
+		return ToDelegate(func, Console.OutputEncoding);
+	}
+
+	/// <summary>
+	/// Creates a pipe target that invokes the specified synchronous delegate on every line written to the stream.
+	/// </summary>
+	public static PipeTarget ToDelegate(Action<string> action, Encoding encoding)
+	{
+		return ToDelegate(
+			line =>
+			{
+				action(line);
+				return Task.CompletedTask;
+			}, encoding);
+	}
+
+	/// <summary>
+	/// Creates a pipe target that invokes the specified synchronous delegate on every line written to the stream.
+	/// Uses <see cref="Console.OutputEncoding" /> for decoding.
+	/// </summary>
+	public static PipeTarget ToDelegate(Action<string> action)
+	{
+		return ToDelegate(action, Console.OutputEncoding);
+	}
+
+	/// <summary>
+	/// Creates a pipe target that replicates data over multiple inner targets.
+	/// </summary>
+	public static PipeTarget Merge(params IEnumerable<PipeTarget> targets)
+	{
+		// optimize targets to avoid unnecessary piping
+		var optimizedTargets = OptimizeTargets(targets);
+
+		return optimizedTargets.Count switch
+		{
+			// avoid merging if there are no targets
+			0 => Null,
+			// avoid merging if there's only one target
+			1 => optimizedTargets.Single(),
+			_ => new AggregatePipeTarget(optimizedTargets)
+		};
+
+		static IReadOnlyList<PipeTarget> OptimizeTargets(IEnumerable<PipeTarget> targets)
+		{
+			var result = new List<PipeTarget>();
+
+			// unwrap merged targets
+			UnwrapTargets(targets, result);
+
+			// filter out no-op
+			result.RemoveAll(t => t == Null);
+
+			return result;
+		}
+
+		static void UnwrapTargets(IEnumerable<PipeTarget> targets, ICollection<PipeTarget> output)
+		{
+			foreach (var target in targets)
+			{
+				if (target is AggregatePipeTarget mergedTarget)
+				{
+					UnwrapTargets(mergedTarget.Targets, output);
+				}
+				else
+				{
+					output.Add(target);
+				}
+			}
+		}
+	}
+}

src/process/Process.Posix.cs

@@ -0,0 +1,46 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+
+namespace Geekeey.Process;
+
+internal sealed partial class Process
+{
+	[SupportedOSPlatform("freebsd")]
+	[SupportedOSPlatform("linux")]
+	[SupportedOSPlatform("macOS")]
+	private static bool SendPosixSignal(int pid, PosixSignals signal)
+	{
+		return Posix.Kill(pid, (int)signal) is 0;
+	}
+
+	[SupportedOSPlatform("freebsd")]
+	[SupportedOSPlatform("linux")]
+	[SupportedOSPlatform("macOS")]
+	internal static partial class Posix
+	{
+		[LibraryImport("libc", EntryPoint = "kill", SetLastError = true)]
+		internal static partial int Kill(int pid, int sig);
+	}
+
+	private enum PosixSignals : int
+	{
+		SIGHUP = 1,
+		SIGINT = 2,
+		SIGQUIT = 3,
+		SIGILL = 4,
+		SIGTRAP = 5,
+		SIGABRT = 6,
+		SIGBUS = 7,
+		SIGFPE = 8,
+		SIGKILL = 9,
+		SIGUSR1 = 10,
+		SIGSEGV = 11,
+		SIGUSR2 = 12,
+		SIGPIPE = 13,
+		SIGALRM = 14,
+		SIGTERM = 15,
+	}
+}

src/process/Process.Windows.cs

@@ -0,0 +1,33 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
+
+namespace Geekeey.Process;
+
+internal sealed partial class Process
+{
+	[SupportedOSPlatform("windows")]
+	private static bool SendCtrlSignal(int processId, ConsoleCtrlEvent ctrl)
+	{
+		return Windows.GenerateConsoleCtrlEvent((uint)ctrl, (uint)processId);
+	}
+
+	[SupportedOSPlatform("windows")]
+	internal static partial class Windows
+	{
+		[LibraryImport("kernel32.dll", SetLastError = true)]
+		[return: MarshalAs(UnmanagedType.Bool)]
+		internal static partial bool GenerateConsoleCtrlEvent(uint dwCtrlEvent, uint dwProcessGroupId);
+	}
+
+	internal enum ConsoleCtrlEvent : uint
+	{
+		CTRL_C_EVENT = 0,        // SIGINT
+		CTRL_BREAK_EVENT = 1,    // SIGQUIT
+		CTRL_CLOSE_EVENT = 2,    // SIGHUP
+		CTRL_LOGOFF_EVENT = 5,   // SIGHUP
+		CTRL_SHUTDOWN_EVENT = 6, // SIGTERM
+	}
+}

src/process/Process.cs

@@ -0,0 +1,181 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+using System.ComponentModel;
+using System.Diagnostics;
+
+namespace Geekeey.Process;
+
+internal sealed partial class Process : IDisposable
+{
+	private readonly TaskCompletionSource _exit = new(TaskCreationOptions.RunContinuationsAsynchronously);
+	private readonly System.Diagnostics.Process _process = new();
+
+	public Process()
+	{
+		// Redirect all standard streams
+		_process.StartInfo.RedirectStandardInput = true;
+		_process.StartInfo.RedirectStandardOutput = true;
+		_process.StartInfo.RedirectStandardError = true;
+		// Do not use the system shell to start the process
+		_process.StartInfo.UseShellExecute = false;
+		// This option only works on Windows and is required there to prevent the
+		// child processes from attaching to the parent console window if one exists.
+		// We need this to be able to send signals to one specific child process,
+		// without affecting any others that may also be running in parallel.
+		_process.StartInfo.CreateNoWindow = true;
+
+		// Only create a new process group on windows to allow sending ctrl-c/ctrl-break signals
+		// without affecting ourselves. This has the implication that the spawned process might not handle
+		// the ctrl-c/ctrl-break signals any more because the process is launched with the CREATE_NEW_PROCESS_GROUP flag.
+		// This is because it disables the default ctrl-c handling for the process.
+		// The process must reenable this behavior itself with a call to `SetConsoleCtrlHandler(null, false)`.
+		// > "If the HandlerRoutine parameter is NULL, a TRUE value causes the calling process to ignore CTRL+C input,
+		// > and a FALSE value restores normal processing of CTRL+C input.
+		// > This attribute of ignoring or processing CTRL+C is inherited by child processes."
+		if (OperatingSystem.IsWindows())
+		{
+			_process.StartInfo.CreateNewProcessGroup = true;
+		}
+	}
+
+	public int Id => _process.Id;
+
+	public string FileName
+	{
+		get => _process.StartInfo.FileName;
+		init => _process.StartInfo.FileName = value;
+	}
+
+	public string Arguments
+	{
+		get => _process.StartInfo.Arguments;
+		init => _process.StartInfo.Arguments = value;
+	}
+
+	public string WorkingDirectory
+	{
+		get => _process.StartInfo.WorkingDirectory;
+		init => _process.StartInfo.WorkingDirectory = value;
+	}
+
+	public IDictionary<string, string?> Environment => _process.StartInfo.Environment;
+
+	// we are purposely using Stream instead of StreamWriter/StreamReader to push the concerns of
+	// writing and reading to PipeSource/PipeTarget at the higher level.
+	public Stream StandardInput => _process.StartInfo.RedirectStandardInput ? _process.StandardInput.BaseStream : Stream.Null;
+
+	public Stream StandardOutput => _process.StartInfo.RedirectStandardOutput ? _process.StandardOutput.BaseStream : Stream.Null;
+
+	public Stream StandardError => _process.StartInfo.RedirectStandardError ? _process.StandardError.BaseStream : Stream.Null;
+
+	// we have to keep track of StartTime ourselves because it becomes inaccessible after the process exits
+	public DateTimeOffset StartTime { get; private set; }
+
+	// we have to keep track of ExitTime ourselves because it becomes inaccessible after the process exits
+	public DateTimeOffset ExitTime { get; private set; }
+
+	public int ExitCode => _process.ExitCode;
+
+	public bool Start(out Exception? exception)
+	{
+		exception = null;
+
+		_process.EnableRaisingEvents = true;
+		_process.Exited += OnProcessExited;
+
+		try
+		{
+			if (!_process.Start())
+			{
+				return false;
+			}
+
+			StartTime = DateTimeOffset.Now;
+		}
+		catch (Win32Exception value)
+		{
+			exception = value;
+			return false;
+		}
+
+		return true;
+
+		void OnProcessExited(object? _, EventArgs args)
+		{
+			_process.Exited -= OnProcessExited;
+			ExitTime = DateTimeOffset.Now;
+			_exit.TrySetResult();
+		}
+	}
+
+	public void Interrupt()
+	{
+		if (TryInterrupt())
+		{
+			return;
+		}
+
+		// In case of failure, revert to the default behavior of killing the process.
+		// Ideally, we should throw an exception here, but this method is called from
+		// a cancellation callback, which would prevent other callbacks from being called.
+		Kill();
+
+		Debug.Fail("Failed to send an interrupt signal.");
+
+		return;
+
+		bool TryInterrupt()
+		{
+			try
+			{
+				if (OperatingSystem.IsWindows())
+				{
+					return SendCtrlSignal(_process.Id, ConsoleCtrlEvent.CTRL_C_EVENT) ||
+						   SendCtrlSignal(_process.Id, ConsoleCtrlEvent.CTRL_BREAK_EVENT);
+				}
+
+				if (OperatingSystem.IsLinux() || OperatingSystem.IsMacOS() || OperatingSystem.IsFreeBSD())
+				{
+					return SendPosixSignal(_process.Id, PosixSignals.SIGINT) ||
+						   SendPosixSignal(_process.Id, PosixSignals.SIGQUIT);
+				}
+
+				// Unsupported platform
+				return false;
+			}
+			catch
+			{
+				return false;
+			}
+		}
+	}
+
+	public void Kill()
+	{
+		try
+		{
+			_process.Kill(entireProcessTree: true);
+		}
+		catch when (_process.HasExited)
+		{
+			// The process has exited before we could kill it. This is fine.
+		}
+		catch
+		{
+			// The process either failed to exit or is in the process of exiting.
+			// We can't really do anything about it, so just ignore the exception.
+			Debug.Fail("Failed to kill the process.");
+		}
+	}
+
+	public async Task WaitForExitAsync(CancellationToken cancellationToken = default)
+	{
+		await _exit.Task.WaitAsync(cancellationToken);
+	}
+
+	public void Dispose()
+	{
+		_process.Dispose();
+	}
+}

src/process/ValidationMode.cs

@@ -0,0 +1,21 @@
+// Copyright (c) The Geekeey Authors
+// SPDX-License-Identifier: EUPL-1.2
+
+namespace Geekeey.Process;
+
+/// <summary>
+/// Strategy used for validating the result of a command execution.
+/// </summary>
+[Flags]
+public enum ValidationMode
+{
+	/// <summary>
+	/// No validation.
+	/// </summary>
+	None = 0b0,
+
+	/// <summary>
+	/// Ensure that the command returned a zero exit code.
+	/// </summary>
+	ZeroExitCode = 0b1,
+}

src/process/package-readme.md

@@ -0,0 +1,51 @@
+Process is a library for interacting with external command-line interfaces. It provides a convenient model for launching
+processes, redirecting input and output streams, awaiting completion, handling cancellation, and more.
+
+## Usage
+
+### Execute a command and capturing its output:
+
+```csharp
+public static async Task<int> Main()
+{
+  var stdout = new StringBuilder();
+  var cmd = new Command("git").WithArguments(["config", "--get", "user.name"]) | stdout;
+  await cmd.ExecuteAsync();
+  Console.WriteLine(stdout.ToString());
+  return 0;
+}
+```
+
+### Execute a command and redirect its output to another command:
+
+```csharp
+public static Task<int> Main()
+{
+  var cmd = new Command("cat").WithArguments(["file.txt"]) | new Command("wc");
+  await cmd.ExecuteAsync();
+  Console.WriteLine(stdout.ToString());
+}
+```
+
+### Execute a command with cancellation support:
+
+```csharp
+public static async Task<int> Main()
+{
+  using var cts = new CancellationTokenSource();
+  Console.CancelKeyPress += (s, e) =>
+  {
+    e.Cancel = true;
+    cts.Cancel();
+  };
+  var cmd = new Command("long-running-command");
+  // kills the process if Ctrl+C is pressed
+  var app = cmd.ExecuteAsync(cts.Token);
+  // manually interrupt after 5 seconds
+  await Task.Delay(5000);
+  app.Interrupt();
+  // wait for process to exit
+  var result = await app;
+  return 0;
+}
+```