Redirect program-output to TMemo in real-time

[Lazarus]

Hi,

I've a problem: I start a Minecraft-Server via LCL's TProcess and I want to read the output.
That's no problem, but I would like to redirect the output to a Memo in real-time ("on-the-fly")!

The output is big!

I've already seen this thread, but it gives me only question marks (?) as output in my memo.

That's what I've already have:

Code: [Select]

procedure TForm1.Button1Click(Sender: TObject);
var
  Process: TProcess;
begin
  Process := TProcess.Create(nil);
  Process.CommandLine := 'java -Xmx1024M -Xms1024M ' + OpenDialog1.FileName + ' nogui';
  Process.Options := [poUsePipes];
 
  Process.Execute;
 
  while Process.Running do
  Memo1.Lines.LoadFromStream(Process.Output);
end;
Thanks for replies,
Lazarus

PS: I started a new topic because I don't want to push old topics .

[KpjComp]

You need some sort of Event loop for grabbing the data from the OuputStream,  LoadFromStream will just block until it read 0 bytes.

I've created a quick example in windows, that does a "Dir c: /s" , this basically lists all files on your C drive, and then outputs the results to a TMemo.  I've just used a TTimer to poll the OutputStream.

[Lazarus]

Thanks for this reply!
I'm very new in Lazarus (around 1 - 2 month).

I tried to recreate your program, but I didn't get it .
Do you mean with "eventloop" a repeat-loop?

Can you maybe give me your source ?

Greetings,
Lazarus

Edit: Sorry, I haven't seen that you have added a attachment ! I'm very new at this board, sorry...
Many thanks anyway! I'll test this now!

[Lazarus]

That's exactly what I needed!!!
Many, many thanks!

I'll try to work with it and implement in my program, when I need some help, I'm going to ask you .

Many thanks again!

Greetings,
Lazarus

[Lazarus]

The TForm1.Timer1Timer-Procedure in your program doesn't work for me because Process.Output isn't assigned yet. Is there a possiblity to start the procedure after the Process is started?

I've already tried to use a while and repeat-loop, but I cannot get it work .

Does anybody have an idea how to get this work?


But by the way: I really love your code! I've never found something easy-understanding like that before! I couldn't imagine it is so easy to solve my problem .

Greetings,
Lazarus

[KpjComp]

Are you on windows?, my example was only windows only.

If you are on windows, could you double check the following command indeed works. -> 

Code: [Select]

c:\windows\system32\cmd.exe /c dir c:\ /s
You might have you system32 directory on a different drive etc.  It works for me on Windows 7 64bit, but I don't have UAC on either, not sure but maybe it could also be permissions, so maybe run as administrator.

Process.Output isn't assigned yet

That's why I have the following on the first line of the Timer event.

Code: [Select]

if not assigned(process.output) then exit; 


[Lazarus]

I'm on Windows 7 32bit and I don't have any problems with your program ! It works very fine on my computer.

My acutal problem is in my program written myself.
It gives me exactly at this line an Execpt-Class "External SIGSEGV" error at the beginning of the program (I start it and the error appears )

That's why I have the following on the first line of the Timer event.

Code: [Select]

if not assigned(process.output) then exit; 


That's very misterious because your program works very well and there's no error.


Thank you for helping me!

Greetings,
Lazarus

[KpjComp]

"External SIGSEGV" error at the beginning of the program

Could it be that Process is not yet defined?.
If you can Zip up your source and attach here, I could have a look.

[Lazarus]

Thank you for your help!

I've attachted the SourceCode.
I would appreciate it, if you could find the mistake


Greeting,
Lazarus

[KpjComp]

Your only creating the instance of Server on the StartServerClick event.

Create the Server / TProcess on the Forms OnCreate Event, also set self as the Owner, and it will free itself when the forms closes.

So, first remove the Server := TProcess.Create(nil) in your StartServerClick Event, and then add this to the OnFormCreateEvent.

Code: [Select]

procedure TMainWindow.FormCreate(Sender: TObject);
begin
  Server := TProcess.Create(self);
end;


[Shebuka]

Or disable Timer until you click on StartServerClick button.

Or assign process=nil in FormCreate and add another check to Timer event like:

Code: [Select]

if (process = nil) then
  exit
else
if not assigned(process.output) then
  exit
else
begin
  // do what you need
end;
EDIT: Thanks KpjComp for correction

[KpjComp]

Code: [Select]

if (process = null) then

I assume you mean nil ?

[Lazarus]

Thanks for your help, you both!

I just had some time again and so I've worked on a little bit on my project.

Unfortunately, I found a bug in the program.
As already said, I plan to redirect the Output of a Minecraft Server into a TMemo.

KpjComp's solution works very well for all programs I've just tested (thanks for that again !) but there's a error with the Minecraft Server. When I start the process, the server,  it redirects the first two lines of the output and then the program hangs up/freezes.

That's a pitty, because your solution works for all other programs !


Thanks in advance (again ) and many greetings,
Lazarus

[Lazarus]

I made a new discovery:
The programm freezes while Minecraft Server is running in the background. While it freezes, of course, no output will be redirected.

But when I force to Minecraft Server to stop via TaskManager, my program doen't freeze anymore, but no output will be redirected

Maybe this helps...

Greetings,
Lazarus

PS: I even tried to change the Timer-Intervall but it makes no difference...

[Lazarus]

Does really nobody have a solution for that problem?

If it helps, I could also add the Source!

Greetings in advance,
Lazarus