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C#•4d ago

standard output from Process not giving any output for certain commands

I am using C# process to run some processes. The shell is cmd.exe, and running several types of scripts work. But, when I try to run python idle with the command cmd.exe /C python, it is giving no output and the process is also not exiting. It should have displayed the idle texts like it do on a normal terminal. The task function in which I am writing the output:

async Task OutputToConsole(StreamReader reader, Process process)
{
    var buffer = new char[128];
    while (true)
    {
        var read = await reader.ReadAsync(buffer, 0, buffer.Length);
        if (read > 0)
        {
            var output = new string(buffer, 0, read);
            Console.Write(output);
        }

        if (process.HasExited && read == 0) break;
    }
}

async Task OutputToConsole(StreamReader reader, Process process)
{
    var buffer = new char[128];
    while (true)
    {
        var read = await reader.ReadAsync(buffer, 0, buffer.Length);
        if (read > 0)
        {
            var output = new string(buffer, 0, read);
            Console.Write(output);
        }

        if (process.HasExited && read == 0) break;
    }
}

Is my approach wrong? Thank you!

54 Replies

SparkyCracked•4d ago

Hey @Abdesol When you run 'python' from cmd.exe, it typically starts Python in the interactive mode if you're in the terminal but may behave differently when started from another process like through C#. So just make sure you calling the right executable. Another option if the above doesn't work is just to redirect the input and output and potentially the error streams. Your method for reading the output looks correct from my stance, just make sure there is output to be read though

Abdesol•4d ago

I think that is the problem as well.. running python.exe is not giving any output, maybe cuz it is interactive but powershell works, but when I run wsl, I don't get the first color full part of it.. I mean the path of files is some how colorful and it is not being captured by the program I am redirecting the error as well.. it uses this function and runs on a separate task

Abdesol•4d ago

but it doesn't look interactive to me

No description

SparkyCracked•4d ago

Ok wait, I am not sure what your goal is here @Abdesol

Abdesol•4d ago

I am basically building a simple terminal. I have got many things sorted out, but the problems now are: 1. python and some commands are not giving output at all 2. some commands like "git clone", which show progress on the same line of console, instead of a new line, I am not able to capture those lines

SparkyCracked•4d ago

If you wanna run python scripts, you can run the a file with the script in it...if you wanna see colors then emulating a terminal will help

Abdesol•4d ago

with files/scripts, it works well, I know handling an interactive processes in a simple terminal project is not going to go easily but that python doesn't look interactive.. the main problem right now is the second one here

SparkyCracked•4d ago

Yeah it would, because you running python the way a user will logically speaking

Abdesol•4d ago

yeah, there is no actual need to run the idle

SparkyCracked•4d ago

It will run python code...and has it's set of memory. If you open cmd and type python, then create variables and print them it will show output

Abdesol•4d ago

yeah, on cmd and powershell it works, it is just not working in my code

Abdesol•4d ago

this is my terminal and it is stuck like this when I run the python command

No description

SparkyCracked•4d ago

But going back to your core issues. For interactive commands like Python, the issue is often related to the command's environment detection. Python, when launched in interactive mode, expects an interactive terminal. When it detects that it is not attached to an interactive terminal (like when standard output is redirected in a C# Process), it might behave differently Try running python scripts in non-interactive modes, you can execute the scripts with predefined inputs, or using -c command to execute a piece of python code. Additionally you can look into 'pseudo-terminal'. It's a little complex in windows but can be partially simulated using third party libraries like wimpty or something names 'Console Terminal' (I forgot it's name but something like that).

Abdesol•4d ago

ah, interesting, I understand the problem now.. but for the second issue, what do you have to say about it? like when running a git clone command, it doesn't go beyond this, but it is actually doing the job and did actually clone it

Abdesol•4d ago

it finishes just like his

No description

SparkyCracked•4d ago

With regards to git clone, commands like that output progress dynamically by rewriting lines. It uses \r as carriage returns intend of \n and some standard output redirects may not handle that well. So you can either read raw output (which I like to do most of the time) and when you detect \r then treat it as an instruction to overwrite the current line in your output display. busy typing lol, I take some time give me a minute lol.

Abdesol•4d ago

hehe, thank you 😅 let me try to remove any /r from the output provided and see if it prints everything first not working this way

SparkyCracked•4d ago

For the git I can give you some code as I have done this before:

c#
StringBuilder currentLine = new StringBuilder();
while (!reader.EndOfStream || !process.HasExited)
{
    int c = reader.Read();
    if (c == -1) { if (process.HasExited) break; else continue; }

    char ch = (char)c;
    if (ch == '\r') {
        Console.Write(currentLine.ToString());
        Console.Write('\r');
        currentLine.Clear();
    } else if (ch == '\n') {
        Console.WriteLine(currentLine.ToString());
        currentLine.Clear();
    } else {
        currentLine.Append(ch);
    }
}
if (currentLine.Length > 0)
    Console.WriteLine(currentLine.ToString());

c#
StringBuilder currentLine = new StringBuilder();
while (!reader.EndOfStream || !process.HasExited)
{
    int c = reader.Read();
    if (c == -1) { if (process.HasExited) break; else continue; }

    char ch = (char)c;
    if (ch == '\r') {
        Console.Write(currentLine.ToString());
        Console.Write('\r');
        currentLine.Clear();
    } else if (ch == '\n') {
        Console.WriteLine(currentLine.ToString());
        currentLine.Clear();
    } else {
        currentLine.Append(ch);
    }
}
if (currentLine.Length > 0)
    Console.WriteLine(currentLine.ToString());

So you basically checking characters and when it finds the \r it will then reset the line buffer.

Abdesol•4d ago

oh interesting.. let me check it rq

Abdesol•4d ago

@SparkyCracked even with your code, by replacing it above in my function, I faced the same issue again

No description

Abdesol•4d ago

I tried adding Console.WriteLine("Here") in the if condition and it was not printing that.. I think there was no /r text ig

SparkyCracked•4d ago

Yeah...tough. Are you able to get the raw outputs? Put a break and see what the variables are

Abdesol•4d ago

okay weird problem after it finished the first line i.e. Clonning into 'My-Website'...

SparkyCracked•4d ago

It just ended?

Abdesol•4d ago

EndOfStream got to tru

No description

Abdesol•4d ago

yep

async Task ExecuteCommand(string command, string workingDirectory)
{
    try
    {
        var processStartInfo = new ProcessStartInfo
        {
            FileName = shell,
            Arguments = commandPrefix + command + commandSuffix,
            WorkingDirectory = workingDirectory,
            RedirectStandardOutput = true,
            RedirectStandardInput = true,
            RedirectStandardError = true,
            UseShellExecute = false,
            CreateNoWindow = true
        };

        using var process = new Process();
        process.StartInfo = processStartInfo;
        process.Start();

        var outputTask = OutputToConsole(process.StandardOutput, process);
        var errorTask = OutputToConsole(process.StandardError, process);
        var inputTask = InputToProcess(process);

        await process.WaitForExitAsync();

        await Task.WhenAll(outputTask, errorTask, inputTask);
    }
    catch (Exception e)
    {
        Console.WriteLine($"ErrorN: {e}");
    }
}

async Task ExecuteCommand(string command, string workingDirectory)
{
    try
    {
        var processStartInfo = new ProcessStartInfo
        {
            FileName = shell,
            Arguments = commandPrefix + command + commandSuffix,
            WorkingDirectory = workingDirectory,
            RedirectStandardOutput = true,
            RedirectStandardInput = true,
            RedirectStandardError = true,
            UseShellExecute = false,
            CreateNoWindow = true
        };

        using var process = new Process();
        process.StartInfo = processStartInfo;
        process.Start();

        var outputTask = OutputToConsole(process.StandardOutput, process);
        var errorTask = OutputToConsole(process.StandardError, process);
        var inputTask = InputToProcess(process);

        await process.WaitForExitAsync();

        await Task.WhenAll(outputTask, errorTask, inputTask);
    }
    catch (Exception e)
    {
        Console.WriteLine($"ErrorN: {e}");
    }
}

this is the function where I am dealing with the process and the tasks.. is there anything I am missing here?

SparkyCracked•4d ago

It looks fine from my side, I don't see any issues

Abdesol•4d ago

for windows no suffix, and the prefix is /C and shell is cmd.exe

SparkyCracked•4d ago

There might be a potential race condition where the process exits before all output has been read. To mitigate this, consider awaiting the I/O tasks before awaiting process.WaitForExitAsync(). This ensures that all output is captured even if the process exits quickly:

c#
var outputTask = OutputToConsole(process.StandardOutput, process);
var errorTask = OutputToConsole(process.StandardError, process);
var inputTask = InputToProcess(process);

await Task.WhenAll(outputTask, errorTask, inputTask);
await process.WaitForExitAsync();

c#
var outputTask = OutputToConsole(process.StandardOutput, process);
var errorTask = OutputToConsole(process.StandardError, process);
var inputTask = InputToProcess(process);

await Task.WhenAll(outputTask, errorTask, inputTask);
await process.WaitForExitAsync();

Abdesol•4d ago

oh, interesting.. let me check rq

SparkyCracked•4d ago

Here is some documentation on race conditions

Race conditions and deadlocks - Visual Basic

This article describes that Visual Basic offers the ability to use threads in Visual Basic applications for the first time. Threads introduce debugging issues such as race conditions and deadlocks.

SparkyCracked•4d ago

I've recently been diving deep into tasks and threading so yeah

Abdesol•4d ago

okay will check it out

Abdesol•4d ago

I tried putting a console write line outside the while loop and the problem is still around

No description

Abdesol•4d ago

the first one is from the error output, and the second one is from the actual output actually, I just checked and the error task is the one responsible for the git clone output

SparkyCracked•4d ago

For me I want to see if you ever have more than that one in your code at any point. So when you step in your code, once you print out 'Cloning into...' hover over the variable and see what it's contents are

Abdesol•4d ago

may I share the code? it is just a one file code

SparkyCracked•4d ago

Ohh fair, if you comfortable with that...

Abdesol•4d ago

yeah, I will probably make this simple terminal public if it gets to work well what was the way to share it? binpath? could you share the link

SparkyCracked•4d ago

$code

MODiX•4d ago

To post C# code type the following: ```cs // code here ``` Get an example by typing $codegif in chat For longer snippets, use: https://paste.mod.gg/

SparkyCracked•4d ago

You can use the above link

Abdesol•4d ago

https://paste.mod.gg/bzkdrnmwuvvs/1

BlazeBin - bzkdrnmwuvvs

A tool for sharing your source code with the world!

Abdesol•4d ago

@SparkyCracked sorry not this one ig

Abdesol•4d ago

https://paste.mod.gg/mxifcyrdlkeu/0

BlazeBin - mxifcyrdlkeu

A tool for sharing your source code with the world!

Abdesol•4d ago

that is the old one

SparkyCracked•4d ago

Ok cool

Abdesol•4d ago

btw, you have to click enter to get back to the path part that is an issue for later

SparkyCracked•4d ago

@Abdesol Some progress... I've located a potential issue where the output capturing from the process in C# is not handling the asynchronous nature of the git clone operation correctly. It's super weird so I am gonna try see if I can read the outputs properly and prevent early termination of the process (I mean git still clones cause my massive project managed to clone so it works which is good)

Abdesol•4d ago

great! and yeah, it does actually clone, just doesn't show the progress bar and the lines that come after that

SparkyCracked•4d ago

Ok @Abdesol I can't lie, it may take me some time to figure this out. I managed to get it to the point where it exits the cloning process when done and waits for input again by itself but the actual printing of output is a little tougher. I don't understand the reason it is bombing out as of yet

Abdesol•3d ago

ah, I really appreciate your cooperation and absolutely no rush @SparkyCracked Sup, any progress?

SparkyCracked•3d ago

Yoo wassup i capped myself to 45 min yesterday on working on it, still at the same place. Will look into it today again.

Abdesol•2d ago

okay, tnx

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