Asmichi.ChildProcess 0.13.0

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Asmichi.ChildProcess

A .NET library that provides functionality for creating child processes. Easier, less error-prone, more flexible than System.Diagnostics.Process at creating and interacting with child processes.

This library can be obtained via NuGet.

See the Wiki for the goals and the roadmap.

Comparison with System.Diagnostics.Process

• Concentrates on creating a child process and obtaining its output.
  • Cannot query status of a process.
  • Cannot create a resident process.
• More destinations of redirection:
  • NUL
  • File (optionally appended)
  • Pipe
  • Handle
• Less error-prone default values for redirection:
  • stdin to NUL
  • stdout to the current stdout
  • stderr to the current stderr
• Pipes are asynchronous; asynchronous reads and writes will be handled by IO completion ports.
• Ensures termination of child processes

License

The MIT License

Supported Runtimes

• .NET Core 3.1 or later

RIDs:

• win10-x86 (not tested)
• win10-x64 (1809 or later; tested on 1809)
• win10-arm (not tested)
• win10-arm64 (not tested)
• linux-x64 (tested on Ubuntu 18.04)
• linux-arm (not tested)
• linux-arm64 (not tested)
• linux-musl-arm64 (not tested)
• linux-musl-x64 (tested on Alpine 3.13)
• osx-x64 (macOS 10.15 Catalina or later; tested on 10.15)
• osx-arm64 (macOS 11.0 Big Sur or later; not tested)

NOTE: On glibc-based Linux, the system must have glibc 2.x.y or later and libstdc++ 3.x.y or later.

NOTE: osx-arm64 will be introduced on .NET 6. dotnet/runtime#43313

Known Issues

• On Windows 10 1809 (including Windows Server 2019), SignalTermination just forcibly kills the process tree (the same operation as Kill).
  • This is due to a Windows pseudoconsole bug where ClosePseudoConsole does not terminate applications attached to the pseudoconsole.
• On macOS prior to 11.0, ExitCode for processes killed by a signal will always be -1.
  • This is due to a waitid bug where it returns 0 in siginfo_t.si_status for such processes.

Notes

• When completely rewriting environment variables with ChildProcessCreationContext or ChildProcessFlags.DisableEnvironmentVariableInheritance, it is recommended that you include basic environment variables such as SystemRoot, etc.

Limitations

• More than 2^63 processes cannot be created.

Assumptions on Runtimes

This library assumes that the underlying runtime has the following characteristics:

• Windows
  • The inner value of a SafeFileHandle is a file handle.
  • The inner value of a SafeWaitHandle is a handle that WaitForSingleObject can wait for.
  • The inner value of a SafeProcessHandle is a process handle.
• *nix
  • The inner value of a SafeFileHandle is a file descriptor.
  • The inner value of a SafeProcessHandle is a process id.
  • Socket.Handle returns a socket file descriptor.

Examples

See ChildProcess.Example for more examples.

Basic

var si = new ChildProcessStartInfo("cmd", "/C", "echo", "foo")
{
    StdOutputRedirection = OutputRedirection.OutputPipe,
    // Works like 2>&1
    StdErrorRedirection = OutputRedirection.OutputPipe,
};

using (var p = ChildProcess.Start(si))
{
    using (var sr = new StreamReader(p.StandardOutput))
    {
        // "foo"
        Console.Write(await sr.ReadToEndAsync());
    }
    await p.WaitForExitAsync();
    // ExitCode: 0
    Console.WriteLine("ExitCode: {0}", p.ExitCode);
}

Redirection to File

var si = new ChildProcessStartInfo("cmd", "/C", "set")
{
    ExtraEnvironmentVariables = new Dictionary<string, string> { { "A", "A" } },
    StdOutputRedirection = OutputRedirection.File,
    StdErrorRedirection = OutputRedirection.File,
    StdOutputFile = "env.txt",
    StdErrorFile = "env.txt",
    Flags = ChildProcessFlags.UseCustomCodePage,
    CodePage = Encoding.Default.CodePage, // UTF-8
};

using (var p = ChildProcess.Start(si))
{
    await p.WaitForExitAsync();
}

// A=A
// ALLUSERSPROFILE=C:\ProgramData
// ...
Console.WriteLine(File.ReadAllText("env.txt"));