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How to use an interactive command line program from another .NET program

I need to write a wrapper for an interactive command line program.
That means I need to be able to send commands to the other program via its standard input und receive the response via its standard output.
The problem is, that the standard output stream seems to be blocked while the input stream is still open. As soon as I close the input stream I get the response. But then I cannot send more commands.
This is what I am using at the moment (mostly from here):
void Main() {
Process process;
process = new Process();
process.StartInfo.FileName = "atprogram.exe";
process.StartInfo.Arguments = "interactive";
// Set UseShellExecute to false for redirection.
process.StartInfo.UseShellExecute = false;
process.StartInfo.CreateNoWindow = true;
// Redirect the standard output of the command.
// This stream is read asynchronously using an event handler.
process.StartInfo.RedirectStandardOutput = true;
// Set our event handler to asynchronously read the output.
process.OutputDataReceived += (s, e) => Console.WriteLine(e.Data);
// Redirect standard input as well. This stream is used synchronously.
process.StartInfo.RedirectStandardInput = true;
process.Start();
// Start the asynchronous read of the output stream.
process.BeginOutputReadLine();
String inputText;
do
{
inputText = Console.ReadLine();
if (inputText == "q")
{
process.StandardInput.Close(); // After this line the output stream unblocks
Console.ReadLine();
return;
}
else if (!String.IsNullOrEmpty(inputText))
{
process.StandardInput.WriteLine(inputText);
}
}
}
I also tried reading the standard output stream synchronously, but with the same result. Any method call on the output stream block indefinitely until the input stream is closed - even Peek() and EndOfStream.
Is there any way to communicate with the other process in a full duplex kind of way?

I tried to reproduce your problem with a small test suite of my own.
Instead of using event handlers I do it in the most trivial way I could conceive: Synchronously. This way no extra complexity is added to the problem.
Here my little "echoApp" I wrote in rust, just for the giggles and also to have a chance to run into the eternal line termination wars problem ( \n vs \r vs \r\n). Depending on the way your command line application is written, this could indeed be one of your problems.
use std::io;
fn main() {
let mut counter = 0;
loop {
let mut input = String::new();
let _ = io::stdin().read_line(&mut input);
match &input.trim() as &str {
"quit" => break,
_ => {
println!("{}: {}", counter, input);
counter += 1;
}
}
}
}
And - being a lazy bone who does not like creating a solution for such a small test, I used F# instead of C# for the controlling side - it is easy enough to read I think:
open System.Diagnostics;
let echoPath = #"E:\R\rustic\echo\echoApp\target\debug\echoApp.exe"
let createControlledProcess path =
let p = new Process()
p.StartInfo.UseShellExecute <- false
p.StartInfo.RedirectStandardInput <- true
p.StartInfo.RedirectStandardOutput <- true
p.StartInfo.Arguments <- ""
p.StartInfo.FileName <- path
p.StartInfo.CreateNoWindow <- true
p
let startupControlledProcess (p : Process) =
if p.Start()
then
p.StandardInput.NewLine <- "\r\n"
else ()
let shutdownControlledProcess (p : Process) =
p.StandardInput.WriteLine("quit");
p.WaitForExit()
p.Close()
let interact (p : Process) (arg : string) : string =
p.StandardInput.WriteLine(arg);
let o = p.StandardOutput.ReadLine()
// we get funny empty lines every other time...
// probably some line termination problem ( unix \n vs \r\n etc -
// who can tell what rust std::io does...?)
if o = "" then p.StandardOutput.ReadLine()
else o
let p = createControlledProcess echoPath
startupControlledProcess p
let results =
[
interact p "Hello"
interact p "World"
interact p "Whatever"
interact p "floats"
interact p "your"
interact p "boat"
]
shutdownControlledProcess p
Executing this in f# interactive (CTRL-A ALT-Enter in Visual Studio) yields:
val echoPath : string = "E:\R\rustic\echo\echoApp\target\debug\echoApp.exe"
val createControlledProcess : path:string -> Process
val startupControlledProcess : p:Process -> unit
val shutdownControlledProcess : p:Process -> unit
val interact : p:Process -> arg:string -> string
val p : Process = System.Diagnostics.Process
val results : string list =
["0: Hello"; "1: World"; "2: Whatever"; "3: floats"; "4: your"; "5: boat"]
val it : unit = ()
I could not reproduce any blocking or deadlocks etc.
So, in your case I would try to investigate if maybe your NewLine property needs some tweaking (see function startupControlledProcess. If the controlled application does not recognize an input as a line, it might not respond, still waiting for the rest of the input line and you might get the effect you have.

process.BeginOutputReadLine();
Doesn't work like expected, because it waits until output stream will be closed, which will happen when process will end, and process will end when its input stream will be closed.
As workaround just use combinations of process.StandardOutput.ReadLine() and asynchronous made by yourself

Check for open Windows application and wait until it is closed?

I have a pretty simple program where it runs certain steps. Each step should run pragmatically. I am having trouble with a bit of my code. Where I am relying on an application to close (waiting for user to close OUTLOOK ) to execute my next block of code. It launches the first file fine but it reads OUTLOOK as open then it wont work. I wish to make it that when the user closes outlook it will continue and open the next HTML file I have tried to Google for something like wait for exit on this line of code Process[] localByName = Process.GetProcessesByName("OUTLOOK");
but I couldnt find anything
static void Main(string[] args)
{
var myProcess = new Process { StartInfo = new ProcessStartInfo(#"c:\TestFile1.html") };
myProcess.Start();
//Launches the html file
Thread.Sleep(1000);
Process[] localByName = Process.GetProcessesByName("OUTLOOK");
//used for detecting whether outlook is open
if (localByName.Length == 0)
{
//Only runs when outlook is closed by user
var myProcess2 =
new Process { StartInfo = new ProcessStartInfo(#"c:\TESTFILE2.html") };
myProcess2.Start();
}
else
{
Console.WriteLine("Im not going to work " + localByName.Length);
Console.ReadLine();
}
}

You are searching for the Process.WaitForExit()Method ( https://msdn.microsoft.com/library/fb4aw7b8(v=vs.110).aspx)
You can use it like:
foreach(var process in localByName) {
if(!process.HasExited()) {
process.WaitForExit();
}
}

Sending message from one C# console application to another

First of all, I've read all related topics and they gave general idea but implementation doesn't work for me:
Send strings from one console application to another
How to send input to the console as if the user is typing?
Sending input/getting output from a console application (C#/WinForms)
I have a console application that is doing some actions in background until cancellation is requested. Typical usage scenario is :
1) Execute application
2) Enter input data
3) Issue start command
4) After some time passes, enter stop command
5) Exit application
Child application Program.cs :
static void Main()
{
Console.WriteLine("Enter input parameter : ");
var inputParameter = Console.ReadLine();
Console.WriteLine("Entered : " + inputParameter);
var tokenSource = new CancellationTokenSource();
var token = tokenSource.Token;
Task.Factory.StartNew(() =>
{
while (true)
{
if (token.IsCancellationRequested)
{
Console.WriteLine("Stopping actions");
return;
}
// Simulating some actions
Console.Write("*");
}
}, token);
if (Console.ReadKey().KeyChar == 'c')
{
tokenSource.Cancel();
Console.WriteLine("Stop command");
}
Console.WriteLine("Finished");
Console.ReadLine();
}
What I'm looking for is some sort of host utility to control this application - spawn multiple instances and perform required user actions on each instance.
Host application Program.cs :
static void Main()
{
const string exe = "Child.exe";
var exePath = System.IO.Path.GetFullPath(exe);
var startInfo = new ProcessStartInfo(exePath)
{
RedirectStandardOutput = true,
RedirectStandardInput = true,
WindowStyle = ProcessWindowStyle.Hidden,
WindowStyle = ProcessWindowStyle.Maximized,
CreateNoWindow = true,
UseShellExecute = false
};
var childProcess = new Process { StartInfo = startInfo };
childProcess.OutputDataReceived += readProcess_OutputDataReceived;
childProcess.Start();
childProcess.BeginOutputReadLine();
Console.WriteLine("Waiting 5s for child process to start...");
Thread.Sleep(5000);
Console.WriteLine("Enter input");
var msg = Console.ReadLine();
// Sending input parameter
childProcess.StandardInput.WriteLine(msg);
// Sending start command aka any key
childProcess.StandardInput.Write("s");
// Wait 5s while child application is working
Thread.Sleep(5000);
// Issue stop command
childProcess.StandardInput.Write("c");
// Wait for child application to stop
Thread.Sleep(20000);
childProcess.WaitForExit();
Console.WriteLine("Batch finished");
Console.ReadLine();
}
When I run this tool, after first input it crashes with "has stopped working" error and prompt to send memory dump to Microsoft. Output window in VS shows no exceptions.
Guess this problem occurs somewhere between applications and may be because of output stream buffer overflow (child app is writing a lot of stars each second which mimics real output which may be huge) and I yet have no idea how to fix it. I don't really need to pass child's output to host (only send start-stop commands to child), but commenting RedirectStandardOutput and OutputDataReceived doesn't fix this problem. Any ideas how to make this work?

I would recommend using NamedPipeServerStream and NamedPipeClientStream, which allows you to open a stream which will communicate between processes on a given machine.
First, this will create a pipe server stream and wait for someone to connect to it:
var stream = new NamedPipeServerStream(this.PipeName, PipeDirection.InOut);
stream.WaitForConnection();
return stream;
Then, this will connect to that stream (from your other process), allowing you to read / write in either direction:
var stream = new NamedPipeClientStream(".", this.PipeName, PipeDirection.InOut);
stream.Connect(100);
return stream;

Another alternative is to use MSMQ, you can find a good tutorial here

I would advise to look to the Working with memory mapped files in .NET 4
http://blogs.msdn.com/b/salvapatuel/archive/2009/06/08/working-with-memory-mapped-files-in-net-4.aspx
It's fast and efficient.

Redirect console input and output to a textbox

Hi there and thanking in advance
I am trying (very hard) to redirect Console input and output into a textbox. So far output is working fine but the trouble is with input.
For example I cannot execute a simple program that will do the following:
Console.WriteLine("Please enter your name: ");
string name = Console.ReadLine();
Console.WriteLine("Hi there " + name);
The reason I can't achieve this is because that the program has to stop while waiting for user to type his/her name and press enter. If I wait for user input on a new thread then the main GUI thread freezes and the textbox can never receive the KeyPress. This thing has me totally stumped. Any advice (or better still code) would be greatly appreciated.
Cheers

The code below is a Console app that calls another console app to do some work and not a WinForm app, but you could easily replace the event handlers (TransformProcessOutputDataReceived, and TransformProcessErrorDataReceived) to output to a text box instead of a TextWriter. Unfortunately it doesn't directly address your issue of the called console application waiting for user input. The code below does pump some input to the called console app via standard input, so perhaps you could supply it from your windows app in the same manner.
Hope this was helpful, I had a heck of a time getting it to work originally myself, sorry I forgot the original references I had used, it was a while ago.
private static void ProcessRetrievedFiles(List<string> retrievedFiles)
{
Console.WriteLine();
Console.WriteLine("Processing retrieved files:");
Console.WriteLine("---------------------------");
Console.WriteLine();
foreach (string filePath in retrievedFiles)
{
if (String.IsNullOrEmpty(filePath)) continue;
Console.WriteLine(filePath);
Process transformProcess = new Process();
string baseOutputFilePath = Path.Combine(ExportDirectory, Path.GetFileNameWithoutExtension(filePath));
transformProcess.StartInfo.FileName = TransformerExecutablePath;
transformProcess.StartInfo.Arguments = string.Format(
"-i:\"{0}\" -x:\"{1}\" -o:\"{2}.final.xml\"",
filePath,
string.Empty,
baseOutputFilePath);
transformProcess.StartInfo.UseShellExecute = false;
transformProcess.StartInfo.WindowStyle = ProcessWindowStyle.Hidden;
transformProcess.StartInfo.RedirectStandardError = true;
transformProcess.StartInfo.RedirectStandardOutput = true;
transformProcess.StartInfo.RedirectStandardInput = true;
transformProcess.EnableRaisingEvents = true;
//attach the error/output recievers for logging purposes
transformProcess.ErrorDataReceived += TransformProcessErrorDataReceived;
transformProcess.OutputDataReceived += TransformProcessOutputDataReceived;
ProcessBridgeFileOutputWriter = new StreamWriter(
baseOutputFilePath + ".log",
false);
ProcessBridgeFileOutputWriter.AutoFlush = true;
transformProcess.Start();
transformProcess.BeginOutputReadLine();
transformProcess.BeginErrorReadLine();
//the exe asks the user to press a key when they are done...
transformProcess.StandardInput.Write(Environment.NewLine);
transformProcess.StandardInput.Flush();
//because we are not doing this asynchronously due to output writer
//complexities we don't want to deal with at this point, we need to
//wait for the process to complete
transformProcess.WaitForExit();
ProcessBridgeFileOutputWriter.Close();
ProcessBridgeFileOutputWriter.Dispose();
//detach the error/output recievers
transformProcess.ErrorDataReceived -= TransformProcessErrorDataReceived;
transformProcess.OutputDataReceived -= TransformProcessOutputDataReceived;
}
}
static void TransformProcessOutputDataReceived(object sender, DataReceivedEventArgs e)
{
if (!string.IsNullOrEmpty(e.Data))
{
ProcessBridgeFileOutputWriter.WriteLine(e.Data);
}
}
static void TransformProcessErrorDataReceived(object sender, DataReceivedEventArgs e)
{
if (!string.IsNullOrEmpty(e.Data))
{
ProcessBridgeFileOutputWriter.WriteLine(string.Format("ERROR: {0}", e.Data));
}
}

Hanging process when run with .NET Process.Start -- what's wrong?

I wrote a quick and dirty wrapper around svn.exe to retrieve some content and do something with it, but for certain inputs it occasionally and reproducibly hangs and won't finish. For example, one call is to svn list:
svn list "http://myserver:84/svn/Documents/Instruments/" --xml --no-auth-cache --username myuser --password mypassword
This command line runs fine when I just do it from a command shell, but it hangs in my app. My c# code to run this is:
string cmd = "svn.exe";
string arguments = "list \"http://myserver:84/svn/Documents/Instruments/\" --xml --no-auth-cache --username myuser --password mypassword";
int ms = 5000;
ProcessStartInfo psi = new ProcessStartInfo(cmd);
psi.Arguments = arguments;
psi.RedirectStandardOutput = true;
psi.WindowStyle = ProcessWindowStyle.Normal;
psi.UseShellExecute = false;
Process proc = Process.Start(psi);
StreamReader output = new StreamReader(proc.StandardOutput.BaseStream, Encoding.UTF8);
proc.WaitForExit(ms);
if (proc.HasExited)
{
return output.ReadToEnd();
}
This takes the full 5000 ms and never finishes. Extending the time doesn't help. In a separate command prompt, it runs instantly, so I'm pretty sure it's unrelated to an insufficient waiting time. For other inputs, however, this seems to work fine.
I also tried running a separate cmd.exe here (where exe is svn.exe and args is the original arg string), but the hang still occurred:
string cmd = "cmd";
string arguments = "/S /C \"" + exe + " " + args + "\"";
What could I be screwing up here, and how can I debug this external process stuff?
EDIT:
I'm just now getting around to addressing this. Mucho thanks to Jon Skeet for his suggestion, which indeed works great. I have another question about my method of handling this, though, since I'm a multi-threaded novice. I'd like suggestions on improving any glaring deficiencies or anything otherwise dumb. I ended up creating a small class that contains the stdout stream, a StringBuilder to hold the output, and a flag to tell when it's finished. Then I used ThreadPool.QueueUserWorkItem and passed in an instance of my class:
ProcessBufferHandler bufferHandler = new ProcessBufferHandler(proc.StandardOutput.BaseStream,
Encoding.UTF8);
ThreadPool.QueueUserWorkItem(ProcessStream, bufferHandler);
proc.WaitForExit(ms);
if (proc.HasExited)
{
bufferHandler.Stop();
return bufferHandler.ReadToEnd();
}
... and ...
private class ProcessBufferHandler
{
public Stream stream;
public StringBuilder sb;
public Encoding encoding;
public State state;
public enum State
{
Running,
Stopped
}
public ProcessBufferHandler(Stream stream, Encoding encoding)
{
this.stream = stream;
this.sb = new StringBuilder();
this.encoding = encoding;
state = State.Running;
}
public void ProcessBuffer()
{
sb.Append(new StreamReader(stream, encoding).ReadToEnd());
}
public string ReadToEnd()
{
return sb.ToString();
}
public void Stop()
{
state = State.Stopped;
}
}
This seems to work, but I'm doubtful that this is the best way. Is this reasonable? And what can I do to improve it?

One standard issue: the process could be waiting for you to read its output. Create a separate thread to read from its standard output while you're waiting for it to exit. It's a bit of a pain, but that may well be the problem.

Jon Skeet is right on the money!
If you don't mind polling after you launch your svn command try this:
Process command = new Process();
command.EnableRaisingEvents = false;
command.StartInfo.FileName = "svn.exe";
command.StartInfo.Arguments = "your svn arguments here";
command.StartInfo.UseShellExecute = false;
command.StartInfo.RedirectStandardOutput = true;
command.Start();
while (!command.StandardOutput.EndOfStream)
{
Console.WriteLine(command.StandardOutput.ReadLine());
}

I had to drop an exe on a client's machine and use Process.Start to launch it.
The calling application would hang - the issue ended up being their machine assuming the exe was dangerous and preventing other applications from starting it.
Right click the exe and go to properties. Hit "Unblock" toward the bottom next to the security warning.

Based on Jon Skeet's answer this is how I do it in modern day (2021) .NET 5
var process = Process.Start(processStartInfo);
var stdErr = process.StandardError;
var stdOut = process.StandardOutput;
var resultAwaiter = stdOut.ReadToEndAsync();
var errResultAwaiter = stdErr.ReadToEndAsync();
await process.WaitForExitAsync();
await Task.WhenAll(resultAwaiter, errResultAwaiter);
var result = resultAwaiter.Result;
var errResult = errResultAwaiter.Result;
Note that you can't await the standard output before the error, because the wait will hang in case the standard error buffer gets full first (same for trying it the other way around).
The only way is to start reading them asynchronously, wait for the process to exit, and then complete the await by using Task.WaitAll

I know this is an old post but maybe this will assist someone. I used this to execute some AWS (Amazon Web Services) CLI commands using .Net TPL tasks.
I did something like this in my command execution which is executed within a .Net TPL Task which is created within my WinForm background worker bgwRun_DoWork method which holding a loop with while(!bgwRun.CancellationPending). This contains the reading of the Standard Output from the Process via a new Thread using the .Net ThreadPool class.
private void bgwRun_DoWork(object sender, DoWorkEventArgs e)
{
while (!bgwRun.CancellationPending)
{
//build TPL Tasks
var tasks = new List<Task>();
//work to add tasks here
tasks.Add(new Task(()=>{
//build .Net ProcessInfo, Process and start Process here
ThreadPool.QueueUserWorkItem(state =>
{
while (!process.StandardOutput.EndOfStream)
{
var output = process.StandardOutput.ReadLine();
if (!string.IsNullOrEmpty(output))
{
bgwRun_ProgressChanged(this, new ProgressChangedEventArgs(0, new ExecutionInfo
{
Type = "ExecutionInfo",
Text = output,
Configuration = s3SyncConfiguration
}));
}
if (cancellationToken.GetValueOrDefault().IsCancellationRequested)
{
break;
}
}
});
});//work Task
//loop through and start tasks here and handle completed tasks
} //end while
}

I know my SVN repos can run slow sometimes, so maybe 5 seconds isn't long enough? Have you copied the string you are passing to the process from a break point so you are positive it's not prompting you for anything?