After calling the Process program, the console input cannot be displayed on the terminal

[ymh199478]

Description

hello, I'm not sure if it is a bug, but it seems to be behaving very strangely. This problem only occurs under linux, and the window can run as expected.

I call a git command through Process, and then ReadKey (or read input with input stream) from the console. Under Linux, user input is hidden(Similar to password input). I expect user input can be seen on the terminal.

I reproduced a minimal example the code is as follows, you can also get the complete project through github repo.

static void Main(string[] args)
{
        var inputStream = Console.OpenStandardInput();
        Console.SetIn(new StreamReader(inputStream));

        ListReference();

        Console.WriteLine("Please enter something first:");
        var line = Console.ReadLine();
        Console.WriteLine($"read first: {line}");

        Console.WriteLine("Please enter something second:");
        line = ReadInput(inputStream);
        Console.WriteLine($"read second: {line}");
}

private static void ListReference()
{
       var process = new System.Diagnostics.Process
       {
           StartInfo =
           {
                  FileName = "git",
                  CreateNoWindow = true,
                  UseShellExecute = false,
           },
       };

       var command = "show-ref --head -d";
       process.StartInfo.Arguments = command;
       process.StartInfo.WorkingDirectory = Path.Combine(Environment.CurrentDirectory, "repo");
       process.Start();
       process.WaitForExit();
       process.Close();
 }

private static string ReadInput(Stream inputStream, Encoding encoding = null)
{
       string ret = null;
       encoding ??= Encoding.UTF8;

       // We only correct the position when we allow seek.
       long position = 0;
       if (inputStream.CanSeek)
       {
           position = inputStream.Position;
       }

       using (var reader = new StreamReader(inputStream, encoding,
                true, 128, true))
       {
           ret = reader.ReadLine();

           // We skip this step directly when it is not allowed,
           // because there will be no bugs even if you do not
           // use position correction under the console program.
           // It contains a potential problem: !5
           if (inputStream.CanSeek && !(ret is null))
           {
                 inputStream.Seek(
                        position + encoding.GetByteCount(ret.ToString()) + encoding.GetByteCount(Environment.NewLine),
                        SeekOrigin.Begin);
           }
       }

       return ret;
}

The value of variable line will be the value entered in the terminal，The program can get the input value correctly but when the key is pressed, it will become like a password input. In other words the entered characters are not displayed in the terminal, until after pressing Enter, the program can receive the input value.

If the function ListReference is annotated, it can also run as expected under linux.

The same code under windows and linux resulted in different behaviors. This confused me. Did I do something wrong?

Configuration

• Running computer

$ dotnet --info
It was not possible to find any installed .NET Core SDKs
Did you mean to run .NET Core SDK commands? Install a .NET Core SDK from:
      https://aka.ms/dotnet-download

Host (useful for support):
  Version: 3.1.7
  Commit:  fcfdef8d6b

.NET Core SDKs installed:
  No SDKs were found.

.NET Core runtimes installed:
  Microsoft.NETCore.App 3.1.7 [/usr/share/dotnet/shared/Microsoft.NETCore.App]

To install additional .NET Core runtimes or SDKs:
  https://aka.ms/dotnet-download

$ uname -a
Linux e3e3b80e6c3c 3.10.0-514.el7.x86_64 #1 SMP Tue Nov 22 16:42:41 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

Other information

I guess whether it is due to some behavior in Process that affects the Console.

[ghost]

Tagging subscribers to this area: @eiriktsarpalis, @jeffhandley
See info in area-owners.md if you want to be subscribed.

[eiriktsarpalis]

I can reproduce this in .NET Core 3.1, but not on .NET 5. Minimal repro:

using System;
using System.IO;
using System.Diagnostics;

namespace ConsoleApp4
{
    class Program
    {
        static void Main(string[] args)
        {
            var inputStream = Console.OpenStandardInput();
            Console.SetIn(new StreamReader(inputStream));

            var process = Process.Start("ls");
            process.WaitForExit();

            Console.WriteLine("Please enter something first:");
            var line = Console.ReadLine();
            Console.WriteLine($"read first: {line}");
        }
    }
}

@tmds I presume this was fixed by #39192?

[ymh199478]

Is there an alternative to the 3.x version to solve this problem?

[eiriktsarpalis]

In my tests I was able to make the issue go away by not setting a custom In reader. Is that something you could do in your app?

[tmds]

@tmds I presume this was fixed by #39192?

Yes.

Is there an alternative to the 3.x version to solve this problem?

You can do something that makes .NET Core turn off echoing (I think getting Console.KeyAvailable should be enough), and from then on echo yourself anything read from Console.OpenStandardInput Stream by calling Console.Write*.