I'm currently trying to get the output of an executable console-app into an other one. To be exact, a little overview of what I'm trying to do:
I have one executable which I cannot edit and neither see it's code. It writes some (quite a bunch to be honest) lines into the console when executed.
Now I want to write another executable that starts the one above and reads the things it writes.
Seems simple to me, so I started coding but ended up with an error message saying that StandardOut has not been redirected or the process hasn't started yet.
I tried it using this kinda structure (C#):
Process MyApp = Process.Start(#"C:\some\dirs\foo.exe", "someargs");
MyApp.Start();
StreamReader _Out = MyApp.StandardOutput;
string _Line = "";
while ((_Line = _Out.ReadLine()) != null)
Console.WriteLine("Read: " + _Line);
MyApp.Close();
I can open the executable and it also does open the one inside, but as soon as it comes to reading the returned values, the app crashes.
What am I doing wrong?!
Take a look at the documentation for the Process.StandardOutput property. You will need to set a boolean indicating that you want the stream redirected as well as disabling shell execute.
Note from the documentation:
To use StandardOutput, you must set ProcessStartInfo..::.UseShellExecute to false, and you must set ProcessStartInfo..::.RedirectStandardOutput to true. Otherwise, reading from the StandardOutput stream throws an exception
You would need to change your code a little bit to adjust for the changes:
Process myApp = new Process(#"C:\some\dirs\foo.exe", "someargs");
myApp.StartInfo.UseShellExecute = false;
myApp.StartInfo.RedirectStandardOutput = false;
myApp.Start();
string output = myApp.StandardOutput.ReadToEnd();
p.WaitForExit();
you could try setting processStartInfo.RedirectStandardOutput = true;
As noted above, you can use RedirectStandardOutput as here.
Another, dirtier way is something like
using (Process child = Process.Start
("cmd", #"/c C:\some\dirs\foo.exe someargs > somefilename"))
{
exeProcess.WaitForExit();
}
And then read its output from somefilename
Related
I was trying to start a exe with arguments by Process.Start.
My first try is using Process.Start("Path/of/the/exe", "arguments of exe").
Here's my code snippets:
Process.Start(#"D:\Program Files\ITASCA\UDEC700\Exe64\udecConsole2017.exe", #"call 'D:\Work\202205\20220525\tunnel-for-cmd.txt'");
However the initialization of this exe is a bit slow, and the result is, I can only start the exe but the failed passing arguments. The following is the screenshot:
which is exactly the same result that starts without arguments.
By referencing this post C# - Making a Process.Start wait until the process has start-up, I changed my code as follows:
var process = Process.Start(#"D:\Program Files\ITASCA\UDEC700\Exe64\udecConsole2017.exe", #"call 'D:\Work\202205\20220525\tunnel-for-cmd.txt'");
while (string.IsNullOrEmpty(process.MainWindowTitle))
{
System.Threading.Thread.Sleep(100);
process.Refresh();
}
however these changes does not work.
I think my goal is to wait until exe completely started and then run it with arguments, but I dont know how to implement this.
=====================================================
New additions:
if I type in arguments call 'D:\Work\202205\20220525\tunnel-for-cmd.txt' in this started process, I will get my result:
SO I think the input arguments should be OK?
=======================================
new addition 2:
code for checking outputstream end
It appears this is a console application and you are typing in the console after it starts. This typing is not arguments: Arguments are provided only when starting a new process and never change.
What you are doing is providing something to the standard input of the program. Console programs have three streams the OS provides (one input and two output). You need to redirect these to detect when the program has started and to provide the proper input.
Something like this:
// Start with stdio redirected
var psi = new ProcessStartInfo()
{
UseShellExecute = false,
FileName = #"your exe",
RedirectStandardInput = true,
RedirectStandardOutput = true,
};
var p = System.Diagnostics.Process.Start(psi);
// Read until the udec> prompt
while(true)
{
var line = p.StandardOutput.ReadLine();
if(line.StartsWith("udec>"))
break;
}
// Write the command
p.StandardInput.WriteLine(#"call 'D:\Work\202205\20220525\tunnel-for-cmd.txt'");
// Read the result
p.StandardOutput.ReadToEnd();
This question already has an answer here:
Reading from a process, StreamReader.Peek() not working as expected
(1 answer)
Closed 6 years ago.
I am having trouble setting up a c# application that creates and interacts with a python process1. A simplistic example is given below.
EDIT: Further research on SO unveiled that my question is a possible duplicate. A potentially related known bug in the .NET Framework is duscussed here and here. It seems that back in 2014 the only easy workaround is indeed to ask the child process to write something in both stdOut and stdErr. But I'd like to know if this assumption is correct and wonder if there hasn't been a fix since 2014?
I have to fulfill the following boundary conditions:
I am not able to close the python process after handing over a script or a command, but I have to keep the process alive. Edit: For that reason I can not make use of the Process.WaitForExit() Method
As the std's remain open all the time, I believe I can't check for EndOfStream, as that would require to read to the end of the stream, which does not exist.
Furthermore, my application has to wait for the response of the python process, therefore the asynchronous option using BeginOutputReadLine() with OnOutputDataReceived seems not appropriate to me.
As the commands that will be sent to python are arbitrary user input, pythons result might be either in stdOut or stdErr ("4+7" results in "11" stored in stdOut; "4+a" results in "name 'a' is not defined" in stdErr)
What I do is to:
set up a python process in interactive mode (Argument "-i")
enable redirect of StdIn, Out, and Err
start the process
get StreamReaders and Writers for the Std's
After that, I want to initially check the StdOut and StdErr. I know that python writes the following piece of information to the StdErr
Python 2.7.11 (v2.7.11:6d1b6a68f775, Dec 5 2015, 20:32:19) [MSC
v.1500 32 bit (Intel)] on win32
and I am able to get this line by using errorReader.Peek() and reading character-based from the errorReader 2.
However, the situation with another process might be totally different. Even with Python, I run into the following problem: when I want to initially read from the outputReader, there is nothing contained in it and outputReader.Peek() seems to run into a deadlock. As mentioned above, the same holds for outputReader.EndOfStream or outputReader.ReadToEnd(). So how do I know if the stdOut can be used at all without causing a deadlock?
Code:
// create the python process StartupInfo object
ProcessStartInfo _tempProcessStartInfo = new ProcessStartInfo(#"C:\TMP\Python27\python.exe");
// ProcessStartInfo _tempProcessStartInfo = new ProcessStartInfo(PathToPython + "python.exe");
// python uses "-i" to run in interactive mode
_tempProcessStartInfo.Arguments = "-i";
// Only start the python process, but don't show a (console) window
_tempProcessStartInfo.WindowStyle = ProcessWindowStyle.Minimized;
_tempProcessStartInfo.CreateNoWindow = true;
// Enable the redirection of python process std's
_tempProcessStartInfo.UseShellExecute = false;
_tempProcessStartInfo.RedirectStandardOutput = true;
_tempProcessStartInfo.RedirectStandardInput = true;
_tempProcessStartInfo.RedirectStandardError = true;
// Create the python process object and apply the startupInfos from above
Process _tempProcess = new Process();
_tempProcess.StartInfo = _tempProcessStartInfo;
// Start the process
bool _hasStarted = _tempProcess.Start();
//// ASynch reading seems not appropriate to me:
// _tempProcess.BeginOutputReadLine();
// _tempProcess.BeginErrorReadLine();
// Create StreamReaders and Writers for the Std's
StreamReader outputReader = _tempProcess.StandardOutput;
StreamReader errorReader = _tempProcess.StandardError;
StreamWriter commandWriter = _tempProcess.StandardInput;
// Create StringBuilder that collects results and ErrorMessages
StringBuilder tmp = new StringBuilder("");
// Create temp variable that is used to peek into streams. C# uses -1 to indicate that there is no more byte to read
int currentPeek = -1;
// Get Initial Error Message. In this specific case, this is the python version
tmp.AppendLine("INITIAL ERROR MESSAGE:");
currentPeek = errorReader.Peek();
while (currentPeek >= 0)
{
char text = (char)errorReader.Read();
tmp.Append(text);
currentPeek = errorReader.Peek();
}
// Get initial output Message. In this specific case, this is EMPTY, which seems to cause this problem, as ...
tmp.AppendLine("INITIAL STDOUT MESSAGE:");
//// ... the following command CREATES a well defined output, and afterwards everything works fine (?) but ...
//commandWriter.WriteLine(#"print 'Hello World'");
//// ... without the the above command, neither
//bool isEndOfStream = outputReader.EndOfStream;
//// ... nor
// currentPeek = outputReader.Peek();
//// ... nor
// tmp.AppendLine(outputReader.ReadLine());
//// ... nor
//tmp.AppendLine(outputReader.ReadToEnd());
//// ... works
// Therefore, the following command creates a deadlock
currentPeek = outputReader.Peek();
while (currentPeek >= 0)
{
char text = (char)outputReader.Read();
tmp.Append(text);
currentPeek = errorReader.Peek();
}
_currentPythonProcess = _tempProcess;
return true;
1 An easy fix to this very specific problem is to send a valid command to the process first, for example simply "4", which returns a "4" as well... However, I want to understand how process streams, pipes and the corresponing readers and writers work and how I can use them in C#. Who knows what future brings, maybe I run into buffer problems when pythons response is 2^n+1 bytes long...
2 I know that I can also read line-based. However, the Peek() prevents me from reporting problems that are related to truncated lines.
If you can wait for the process to end and then read the buffers, you might be able to use Process.WaitForExit. There is also another method you can check, Process.WaitForInputIdle, but it depends on the process having a message loop, which I don't think a Python script gets when executing.
I have the code to run a console command/utility, monitor the live output using 'Debug.WriteLine' and write the final output to a log file when needed.
Edit: It does not work for Praatcon.exe an analysis command line utility. It can be downloaded from here . Just invoke praatcon.exe without argument, it should write on 'stdout' about the Usage. The code wont catch it.
The issue is, it works good for certain utilities and I can see the debug output as well as log in the file. But for certain utilities, I see empty commands, even though when I run those commands through a CMD window, I see the output. I am capturing both the streams Output and Error.
Can someone help me with this ?
Full code can be found here
Here is how I am trying to do it
Initialization of ProcessStartInfo
var info = new ProcessStartInfo(command, parameters)
{
WorkingDirectory = workingDirectory,
UseShellExecute = false,
RedirectStandardOutput = true,
RedirectStandardError = true,
CreateNoWindow = true
};
Running the process and initializing the string builders for output and error streams.
var process = Process.Start(info);
var output = new StringBuilder();
var error = new StringBuilder();
Starting the tasks for Reading Streams
var errorTask = process.StandardError.ReadLineAsync();
var lineTask = process.StandardOutput.ReadLineAsync();
Here is my while loop to monitor the progress and write output to the Debug Output window when there is any available.
while (process.HasExited == false)
{
if (lineTask.IsCompleted)
{
output.AppendLine(lineTask.Result);
Debug.WriteLine(lineTask.Result);
lineTask = process.StandardOutput.ReadLineAsync();
}
if (errorTask.IsCompleted)
{
error.AppendLine(errorTask.Result);
Debug.WriteLine(errorTask.Result);
errorTask = process.StandardError.ReadLineAsync();
}
errorTask.Wait(TimeSpan.FromMilliseconds(100.0));
lineTask.Wait(TimeSpan.FromMilliseconds(100.0));
}
After this, I am reading the streams further to see if there is anything left in there.
I get empty strings in output and error for one command. The only thing I get correct is the 'ExitCode'.
Please tell me if there is anything I am doing the wrong way.
As discussed on IRC, there was a possibility that the program you're calling may have been writing to a stream other than standard out or standard error. There are also streams with numbers 3-9 on Windows.
This was not the case with the process you were calling. It was actually using the Win32 call 'WriteConsole', which seems to access the console directly.
It would be possible to move the output back to stderr by preloading a DLL (DLL injection) but this is hackish, so as the source of the program is available, it's perhaps better to 'fix' it or submit a patch to the authors.
Your question is borderline too broad, in that it's missing details, and "anything I am doing the wrong way" is fairly open-ended.
That said, you are doing the reading of the streams the wrong way, in the sense that you should not be polling. I don't see any specific reason that would cause the behavior you've (vaguely) described. But just in case, I offer this correct implementation of the reading:
async Task ConsumeStream(StreamReader reader, StringBuilder builder)
{
string line;
while ((line = await reader.ReadLineAsync()) != null)
{
builder.AppendLine(line);
Debug.WriteLine(line);
}
}
Then call that method like this:
var errorTask = ConsumeStream(process.StandardError, error);
var lineTask = ConsumeStream(process.StandardOutput, output);
// Technically superfluous, since you'll also wait on the tasks,
// but won't hurt.
process.WaitForExit();
Task.WaitAll(errorTask, lineTask);
// error and output StringBuilders will be valid here
If that doesn't help, you'll need to post a better code example, which will allow others to reproduce the actual problem. See https://stackoverflow.com/help/mcve
Our C# (V3.5) application needs to call another C++ executable which is from another company. we need to pass a raw data file name to it, it will process that raw data (about 7MB) file and generate 16 result files (about 124K for each).
The code to call that executable is this:
ProcessStartInfo startInfo = new ProcessStartInfo();
startInfo.CreateNoWindow = true;
startInfo.UseShellExecute = false;
startInfo.RedirectStandardError = true;
startInfo.RedirectStandardOutput = true;
startInfo.WindowStyle = ProcessWindowStyle.Hidden;
startInfo.FileName = exePath;
startInfo.Arguments = rawDataFileName;
try
{
Process correctionProcess = Process.Start(startInfo);
correctionProcess.WaitForExit();
}
catch(nvalidOperationException ex)
{
....
}
catch(...)
...
It works fine. Now we have new raw data. After replace the old raw data with the new raw data file. That executable process never return to us. It will hang forever. If we kill our C# application, those result files will be generated in the target directoy. It looks like the executable does create those result files but has issue to write to the disk and return to us until the process is terminated.
It is NOT like this with the old raw data file.
When we run the executable with the new raw data directly (no from our C# app call), it works fine. This means this executable has no problem with the new raw data.
My question 1: what's the possible causes for this behaviour?
Now I change our code with startInfo.UseShellExecute = true; and add startInfo.WorkingDirectory= ..., and disabled
//startInfo.RedirectStandardError = true;
//startInfo.RedirectStandardOutput = true;
Then it works.
My question 2: why use Windows Shell solve this issue?
My question 3: why it works before without using Shell?
My question 4: when we should use Shell and When shouldn't?
thanks,
Several possibilities:
You are redirecting output and error but not reading it. The process will stall when its stdout or stderr buffer fills up to capacity.
The program might be displaying an error message and waiting for a keypress. You are not redirecting input nor check stderr, that keypress will never come.
Some programs, xcopy.exe is a very good example, require stdin to be redirected when you redirect stdout. Although the failure mode for xcopy.exe is an immediate exit without any diagnostic.
Seeing it fixed when you kill your C# program makes the first bullet the likeliest reason.
I know this, it is a very common problem. I has to do with the output, which must be handled asynchronously. You just can't WaitForExit when output exceeds certain amount of data.
You need to add
myStdErr= correctionProcess.StandardError.ReadToEnd();
Only once usually works, if you want to overkill this works ("P" being my Process)
while (!P.HasExited)
stdErr+= P.StandardError.ReadToEnd();
If you don't need the stdout/stderr, just turn the Redirect* properties to false.
I was following one of the thread to run perl scripts from my c# program.
My c# code is like this:
private void RunScript(ArrayList selectedScriptFileList)
{
foreach (var curScriptFileName in selectedScriptFileList)
{
ProcessStartInfo myProcessStartInfo = new ProcessStartInfo("perl.exe");
myProcessStartInfo.Arguments = (string)(curScriptFileName);
myProcessStartInfo.UseShellExecute = false;
myProcessStartInfo.RedirectStandardOutput = true;
myProcessStartInfo.WindowStyle = ProcessWindowStyle.Hidden;
myProcessStartInfo.CreateNoWindow = true;
myProcess.StartInfo = myProcessStartInfo;
myProcess.Start();
myProcess.WaitForExit();
string output = myProcess.StandardOutput.ReadToEnd();
this.ScriptTestResultTextBox.AppendText(output);
}
}
And my perl script requires XML parsing. I can read the print statement before the XML parsing, but not after the parsing starts. The script runs find on DoS shell.
Here is part of my script:
print("\n");
print("****************** test1.pl ***********************\n");
print("\n");
print("1");
print("2");
my $scriptName = 'test1.pl';
my $file = '../../ScriptParamLib.xml';
my $parser = XML::LibXML->new();
my $tree = $parser->parse_file($file);
my $root = $tree->getDocumentElement;
my #species = $root->getElementsByTagName('test_node');
print("Accessing XML Data Base...\n");
The c# testbox only shows the first three print statement but not the last one.
Does anybody knows why?
Thanks
You could add more debugging print statements (e.g. one between every other line of your code) to see how far the execution gets. However, I'm going to go on a hunch and suggest that adding these three lines to your script will either solve the problem outright or lead you closer to a solution:
use strict;
use warnings;
use XML::LibXML;
Please update your question indicating how far execution gets and what errors you see!
I figured I should roll my comments into an answer since they proved to be helpful:
Since using an absolute path for $file in the Perl script works, the issue most likely has something to do with the working directory of the process that gets spawned from the C# program. You can use the Cwd module in the Perl script to see what the working directory actually is. If it's not what you expect, try setting it via the WorkingDirectory property of ProcessStartInfo in your C# program. Relative paths should work just fine after that.