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C# Show output of Process in real time [duplicate]

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Redirect console output to textbox in separate program
(4 answers)
C# - Capturing Windows Application Output
(3 answers)
Closed 9 years ago.
In C# I am starting a 3rd party application that takes 2 - 3 hours to complete. I need the output of the Process to write to the console in real time. I have done research on BeginOutputReadLine() and RedirectStandardOutput from Microsoft's website but my code is still not working.
Currently my code is only showing the output when the process is finished. I don't know where its gone wrong.
static void Main(string[] args)
{
Process process;
process = new Process();
process.StartInfo.FileName = "C:\\ffmbc\\ffmbc.exe";
process.StartInfo.Arguments = "-i \\\\dssp-isi-t\\TMD\\B002C010_130520_R2R7.2398v5.mxf -an -vcodec libx264 -level 4.1 -preset veryslow -tune film -x264opts bluray-compat=1:weightp=0:bframes=3:nal-hrd=vbr:vbv-maxrate=40000:vbv-bufsize=30000:keyint=24:b-pyramid=strict:slices=4:aud=1:colorprim=bt709:transfer=bt709:colormatrix=bt709:sar=1/1:ref=4 -b 30M -bt 30M -threads 0 -pass 1 -y \\\\dss-isi-t\\MTPO_Transfer\\dbay\\B002C010_130520_R2R7.2398v5.mxf.h264";
process.StartInfo.UseShellExecute = false;
process.StartInfo.CreateNoWindow = true;
process.StartInfo.RedirectStandardOutput = true;
process.OutputDataReceived += new DataReceivedEventHandler(OutputHandler);
process.StartInfo.RedirectStandardInput = true;
process.Start();
process.BeginOutputReadLine();
process.WaitForExit();
process.Close();
}
private static void OutputHandler(object sendingProcess, DataReceivedEventArgs outLine)
{
string line;
line = (outLine.Data.ToString());
Console.WriteLine(line);
}

Similar to a previous question I'd answered, maybe even a duplicate.
See: Pipe a stream to Debug.Write()
Here's my answer (modified slightly) from that:
process.StartInfo.UseShellExecute = false;
process.StartInfo.RedirectStandardOutput = true;
process.OutputDataReceived += p_OutputDataReceived;
process.Start();
process.BeginOutputReadLine();
Then, your event handler for receiving data.
void p_OutputDataReceived(object sender, DataReceivedEventArgs e)
{
Console.Write(e.Data);
}
Basically, you just need to nix the WaitForExit(), since that makes your program hang until the process completes.

The line
process.WaitForExit();
will cause the current program to wait until the given process finishes. This is most certainly not what you want; you probably want to start the process, let it run asynchronously, and then let it tell you when it finishes. For that, you will want to use the process.Exited event.

Process RedirectStandardOutput empty and DataReceivedEventArgs.Data is null

When running an application in console mode there are lines written to the console.
Now I want to do this programmatically. Here is some example code that I used: MSDN on OutputDataReceived Event
private static StringBuilder _sortOutput = null;
var proc = new Process();
var info = new ProcessStartInfo();
info.FileName = #"C:\SomeApp.exe";
info.UseShellExecute = false;
info.WindowStyle = ProcessWindowStyle.Normal;
info.CreateNoWindow = false;
proc.StartInfo = info;
info.RedirectStandardOutput = true;
info.RedirectStandardError = true;
proc.OutputDataReceived += HandleOutputData;
proc.ErrorDataReceived += HandleOutputData;
proc.Start();
proc.BeginOutputReadLine();
proc.BeginErrorReadLine();
proc.WaitForExit();
var exitCode = proc.ExitCode;
var output = _sortOutput.ToString();
private void HandleOutputData(object sender, DataReceivedEventArgs e)
{
_sortOutput.Append(e.Data);
}
But the DataReceivedEventArgs.Data is always null and I do not get back the result which I can see in the console window that opens.
How can I receive the output? Is there a way to achieve that?
UPDATE
I also tried to read the proc.StandardOutput directly, but it does not yield any data.

As someone else has spotted, there is a bug where _sortOutput will be null. But regardless of that, you are completely correct: e.Data can and will be null!
In fact, your handler should always get called with e.Data equal to null when the AsyncStreamReader that is doing the calling reaches EOF of the standard output that is being redirected - which will happen when the process you are running exits. Unless, of course, you deregister your OutputDataReceived event handler first, or cancel asynchronous output redirection.

It's null, because you read the data in var outPut
Try following:
a) Change the way you handle it
proc.OutputDataReceived += new DataReceivedEventHandler(HandleOutputData);
b)Comment out the line
//var outPut = proc.StandardOutput.ReadToEnd();

Null signifies the end of the asynchronous stream.
You must both WaitForExit and wait for the terminating null to come through e.Data

C#: get external shell command result line by line

I am writing a C# winform application that starts a second process to execute shell commands like "dir" and "ping". I redirect the second process's output so my app can receive the command result. It roughly works fine.
The only problem is my winform app receives the command line output as a whole instead of line by line. For example, it has to wait for the external "ping" command to finish (which takes many seconds or longer) and then receives the whole output (many lines) at once.
What I want is the app receives the cmdline output in real-time, i.e. by lines not by block. Is this doable?
I am using this code to read the output:
while ((result = proc.StandardOutput.ReadLine()) != null)
But it does not work the way I expected.
Thanks in advance.
EDIT: here is the code I am using:
System.Diagnostics.ProcessStartInfo procStartInfo = new
System.Diagnostics.ProcessStartInfo("cmd", "/c " + command);
procStartInfo.WindowStyle = ProcessWindowStyle.Hidden;
// The following commands are needed to redirect the standard output.
procStartInfo.RedirectStandardOutput = true;
procStartInfo.UseShellExecute = false;
procStartInfo.CreateNoWindow = true;
// Now we create a process, assign its ProcessStartInfo and start it
System.Diagnostics.Process proc = new System.Diagnostics.Process();
proc.StartInfo = procStartInfo;
proc.Start();
// Get the output into a string
string result;
try {
while ((result = proc.StandardOutput.ReadLine()) != null)
{
AppendRtfText(result+"\n", Brushes.Black);
}
} // here I expect it to update the text box line by line in real time
// but it does not.

Have a look at the example in this msdn article on how to do the reading completly async.
Beyond that I expect your code does to read line by line now but the UI doesn't get any time to repaint (missing Application.DoEvents(); after updating the RTFTextBox

Instead of loop using while ((result = proc.StandardOutput.ReadLine()) != null) you should of using:
...
proc.OutputDataReceived += proc_DataReceived;
proc.Start();
proc.BeginOutputReadLine();
proc.WaitForExit();
This will start asynchronous reading the lines when they arrives, you then handle the lines read by e.Data in proc_DataReceived handler, since you are use BeginOutputReadline the e.Data will be a string lines.

This could be usefull:
http://social.msdn.microsoft.com/Forums/en-US/csharplanguage/thread/8d6cebfc-9b8b-4667-85b5-2b92105cd0b7/
http://www.dotnetperls.com/redirectstandardoutput

I had the same issue and got around it with the following. I found that if I had an error in the external app I was getting no output at all using the ReadToEnd() method, so switched to use the line by line streamreader. Will be switching over to use the answer provided by Saa'd though as that looks like the proper way to handle it.
Also found this solution: c# coding convention public/private contexts which provides for error handling at the same time and giving a fuller explanation to the use of externalApp.OutputDataReceived += (sender, args) => Console.WriteLine(args.Data);
Process externalApp = new Process();
externalApp.StartInfo.FileName = config.ExternalApps + #"\location\DeleteApp.exe";
externalApp.StartInfo.Arguments = Directory.GetCurrentDirectory() + #"\..\..\..\project\argumentsForDeleteApp.xml";
externalApp.StartInfo.WindowStyle = ProcessWindowStyle.Hidden;
externalApp.StartInfo.UseShellExecute = false;
externalApp.StartInfo.RedirectStandardOutput = true;
Console.Out.WriteLine(DateTime.UtcNow.ToLocalTime().ToString() +
":###### External app: " + externalApp.StartInfo.FileName + " - START");
externalApp.Start();
using (StreamReader reader = externalApp.StandardOutput)
{
while (!reader.EndOfStream)
{
string result = reader.ReadLine();
Console.Out.WriteLine(result);
}
}
externalApp.WaitForExit();

process.standardoutput.ReadToEnd() always empty?

I'm starting a console application, but when I redirect the standard output I always get nothing!
When I don't redirect it, and set CreateNoWindow to false, I see everything correctly in the console, but when I redirect it, StandardOutput.ReadToEnd() always returns an empty string.
Process cproc = new Process();
cproc.StartInfo.CreateNoWindow = true;
cproc.StartInfo.FileName = Dest;
cproc.StartInfo.RedirectStandardOutput = true;
cproc.StartInfo.WindowStyle = ProcessWindowStyle.Hidden;
cproc.StartInfo.UseShellExecute = false;
cproc.EnableRaisingEvents = true;
cproc.Start();
cproc.Exited += new EventHandler(cproc_Exited);
while(!stop)
{
result += cproc.StandardOutput.ReadToEnd();
}
The EventHandler cproc_exited just sets stop to true. Can someone explain why result is always string.Empty?

Best way for this is to redirect the output and wait for the events:
// not sure if all this flags are needed
process.StartInfo.CreateNoWindow = true;
process.StartInfo.ErrorDialog = false;
process.StartInfo.UseShellExecute = false;
process.StartInfo.RedirectStandardError = true;
process.StartInfo.RedirectStandardInput = true;
process.StartInfo.RedirectStandardOutput = true;
process.EnableRaisingEvents = true;
process.OutputDataReceived += process_OutputDataReceived;
process.ErrorDataReceived += process_ErrorDataReceived;
process.Exited += process_Exited;
process.Start();
void process_Exited(object sender, System.EventArgs e)
{
// do something when process terminates;
}
void process_OutputDataReceived(object sender, DataReceivedEventArgs e)
{
// a line is writen to the out stream. you can use it like:
string s = e.Data;
}
void process_ErrorDataReceived(object sender, DataReceivedEventArgs e)
{
// a line is writen to the out stream. you can use it like:
string s = e.Data;
}

Why are you looping? Once it's read to the end, it's not going to be able to read any more data, is it?
Are you sure the text is actually being written to StandardOutput rather than StandardError?
(And yes, obviously you want to set RedirectStandardOutput to true rather than false. I assumed that was just a case of you copying the wrong version of your code.)
EDIT: As I've advised in the comments, you should read from standard output and standard error in separate threads. Do not wait until the process has exited - this can end up with a deadlock, where you're waiting for the process to exit, but the process is blocking trying to write to stderr/stdout because you haven't read from the buffer.
Alternatively you can subscribe to the OutputDataReceived and ErrorDataReceived events, to avoid using extra threads.

You have redirection of standard out disabled. Try changing
cproc.StartInfo.RedirectStandardOutput = false;
into
cproc.StartInfo.RedirectStandardOutput = true;
Does the following sample from MSDN work for you?
// Start the child process.
Process p = new Process();
// Redirect the output stream of the child process.
p.StartInfo.UseShellExecute = false;
p.StartInfo.RedirectStandardOutput = true;
p.StartInfo.FileName = "Write500Lines.exe";
p.Start();
// Do not wait for the child process to exit before
// reading to the end of its redirected stream.
// p.WaitForExit();
// Read the output stream first and then wait.
string output = p.StandardOutput.ReadToEnd();
p.WaitForExit();

Get rid of the loop and move the call to ReadToEnd to cproc_Exited.

Redirect console output to textbox in separate program

I'm developing an Windows Forms application that requires me to call a separate program to perform a task. The program is a console application and I need to redirect standard output from the console to a TextBox in my program.
I have no problem executing the program from my application, but I don't know how to redirect the output to my application. I need to capture output while the program is running using events.
The console program isn't meant to stop running until my application stops and the text changes constantly at random intervals. What I'm attempting to do is simply hook output from the console to trigger an event handler which can then be used to update the TextBox.
I am using C# to code the program and using the .NET framework for development. The original application is not a .NET program.
EDIT:
Here's example code of what I'm trying to do. In my final app, I'll replace Console.WriteLine with code to update the TextBox. I tried to set a breakpoint in my event handler, and it isn't even reached.
void Method()
{
var p = new Process();
var path = #"C:\ConsoleApp.exe";
p.StartInfo.FileName = path;
p.StartInfo.UseShellExecute = false;
p.OutputDataReceived += p_OutputDataReceived;
p.Start();
}
static void p_OutputDataReceived(object sender, DataReceivedEventArgs e)
{
Console.WriteLine(">>> {0}", e.Data);
}

This works for me:
void RunWithRedirect(string cmdPath)
{
var proc = new Process();
proc.StartInfo.FileName = cmdPath;
// set up output redirection
proc.StartInfo.RedirectStandardOutput = true;
proc.StartInfo.RedirectStandardError = true;
proc.EnableRaisingEvents = true;
proc.StartInfo.CreateNoWindow = true;
// see below for output handler
proc.ErrorDataReceived += proc_DataReceived;
proc.OutputDataReceived += proc_DataReceived;
proc.Start();
proc.BeginErrorReadLine();
proc.BeginOutputReadLine();
proc.WaitForExit();
}
void proc_DataReceived(object sender, DataReceivedEventArgs e)
{
// output will be in string e.Data
}

You can use the following code
MemoryStream mem = new MemoryStream(1000);
StreamWriter writer = new StreamWriter(mem);
Console.SetOut(writer);
Assembly assembly = Assembly.LoadFrom(#"C:\ConsoleApp.exe");
assembly.EntryPoint.Invoke(null, null);
writer.Close();
string s = Encoding.Default.GetString(mem.ToArray());
mem.Close();

I've added a number of helper methods to the O2 Platform (Open Source project) which allow you easily script an interaction with another process via the console output and input (see http://code.google.com/p/o2platform/source/browse/trunk/O2_Scripts/APIs/Windows/CmdExe/CmdExeAPI.cs)
Also useful for you might be the API that allows the viewing of the console output of the current process (in an existing control or popup window). See this blog post for more details: http://o2platform.wordpress.com/2011/11/26/api_consoleout-cs-inprocess-capture-of-the-console-output/ (this blog also contains details of how to consume the console output of new processes)

Thanks to Marc Maxham for his answer that save me time !
As Jon of All Trades notice it, UseShellExecute must be set to false in order to redirect IO streams, otherwise the Start() call throws an InvalidOperationException.
Here is my modification of the code where txtOut is a WPF readonly Textbox
void RunWithRedirect(string cmdargs)
{
var proc = new Process()
{
StartInfo = new ProcessStartInfo("cmd.exe", "/k " + cmdargs)
{
RedirectStandardOutput = true,
RedirectStandardError = true,
CreateNoWindow = true
},
EnableRaisingEvents = true
};
// see below for output handler
proc.ErrorDataReceived += proc_DataReceived;
proc.OutputDataReceived += proc_DataReceived;
proc.Start();
proc.BeginErrorReadLine();
proc.BeginOutputReadLine();
proc.WaitForExit();
}
void proc_DataReceived(object sender, DataReceivedEventArgs e)
{
if (e.Data != null)
Dispatcher.BeginInvoke(new Action( () => txtOut.Text += (Environment.NewLine + e.Data) ));
}