Hello,

I know XP is an old OS but some customers of mine still have it !

I'm writing a little software which is calling a console program and I have the need to capture its output. My core TPRocess code is the same as fpc wiki for TProcess and it works very well in Windows 7. My problem is Windows XP I mean, the same code seems does not produce any results.

Any tip ?

Thank you
Antonio

Any tip ?

1. Define "does not produce any results."
2. Show your code

2015-03-25 5:01 GMT+01:00 leledumbo :

1. Define "does not produce any results."

Simply I cannot get output from console app which I'm trying to run and capture. Again, this is happening just for windows xp. Same procedure (follow code) in Windows 7 is right.

2. Show your code

Yes, you are absolutely right. Here it is. I did not use RunCommand because it does not seem to work for me. Problem was such as above, I mean no output from console app to run.

---------------------- code ---------------
procedure TBurpClient.Run;
begin
  fOurProcess.Options := [poUsePipes] + [poNoConsole];
  fOurProcess.Execute;
  while True do
  begin
    // make sure we have room
    fMemStream.SetSize(fBytesRead + READ_BYTES);
    // try reading it
    fNumBytes := fOurProcess.Output.Read((fMemStream.Memory +
fBytesRead)^, READ_BYTES);
    if fNumBytes > 0 then // All read() calls will block, except the final one.
    begin
      Inc(fBytesRead, fNumBytes);
     // Write('.') //Output progress to screen.
    end
    else
      BREAK // Program has finished execution.
  end;
  fMemStream.SetSize(fBytesRead);
  fOutputLines := TStringList.Create;
  fOutputLines.LoadFromStream(fMemStream);
  fOutputLines.SaveToFile('output.txt');
  CommandOutput := fOutputLines.Text;
  faStringList.Assign(fOutputLines);
  fObjectList.Add(fOutputLines);
  Inc(fIndexOfOL);
//  fOutputLines.Free;
end;
-------------------------------------------------

Thank you.

I am not sure this is always correct. Various versions of windows work differently in this regard;
zero (0) may be a valid return value. I suggest you check fOurProcess.IsRunning to break the loop.

Michael.

2015-03-25 8:41 GMT+01:00 Michael Van Canneyt :

Thank you, I will try it. But debugging I can see the problem is not in the loop. In Windows XP fNumBytes is always zero:

fNumBytes := fOurProcess.Output.Read((fMemStream.Memory +
fBytesRead)^, READ_BYTES);

so it seems the Read of fOurProcess.Output is not giving the expected results.

In Windows 7 it's ok.

Antonio

Read translates directly to a kernel call.

In Windows 7 it's ok.

Once more:
Zero is a valid return value for read from a pipe.

So it can perfectly be that read attempts 50 times returns 0, and only at read attempt 51 you get a positive result.

That is why you must check isRunning, and not rely on the return value of readbytes.

Michael.

It could also be due to the problem we detected in fpmkunit: If the stderr is a separate pipe and that pipe is full, the inferior will stop until that pipe is read.
See this patch:

http://svn.freepascal.org/cgi-bin/viewvc.cgi/trunk/packages/fcl-process/src/ process.pp?r1=29107&r2=29303

Could the difference between Windows 7 and Windows XP be related to different amount to stderr pipe?
Or maybe the internal pipe size is different?

In the hope this could be useful,

Pierre Muller

Thank you, this is my new code and while it's working good on Windows 7 it doesn't on Windows XP :(.

procedure TBurpClient.Run;
begin
  fOurProcess.Options := [poUsePipes] + [poNoConsole];
  fOurProcess.Execute;
  while fOurProcess.Running do
  begin
    // make sure we have room
    fMemStream.SetSize(fBytesRead + READ_BYTES);
    // try reading it
    fNumBytes := fOurProcess.Output.Read((fMemStream.Memory +
fBytesRead)^, READ_BYTES);
    Inc(fBytesRead, fNumBytes);
  end;
  fMemStream.SetSize(fBytesRead);
  fOutputLines := TStringList.Create;
  fOutputLines.LoadFromStream(fMemStream);
  fOutputLines.SaveToFile('output.txt');
  CommandOutput := fOutputLines.Text;
  faStringList.Assign(fOutputLines);
  fObjectList.Add(fOutputLines);
  Inc(fIndexOfOL);
  Inc(fIndexOfOL);
//  fOutputLines.Free;
end;

Following the suggestion by Pierre:
Try adding [poStderrToOutPut] as well.

Michael.

2015-03-25 10:47 GMT+01:00 Pierre Free Pascal :

Thank you ! I just tried to add [poStderrToOutPut] as Michael adviced into Options but without result.

About your fpc patch, does it mean I will have to try download a svn checkout of fpc compiler and using that one instead of my actual packaged FPC 2.6.4 ?

Thank you
Antonio

Antonio Sanguigni wrote

My problem is Windows XP I mean, the same code seems does not produce any results.

I've used the following code in fpGUI's demo IDE and it works here under FreeBSD, Linux and Win2000-Win7 (I don't have Win8 so can't test that).

The following code executes the FPC compiler an captures the results and triggers an event, which eventually displays the output in a message window.

=============================
procedure TBuilderThread.Execute;
const
  BufSize = 1024; //4096;
var
  p: TProcess;
  c: TfpgString;
  unitdir: TfpgString;
  Buf: string;
  Count: integer;
  i: integer;
  LineStart: integer;
begin
  unitdir := GProject.ProjectDir + GProject.UnitOutputDir;
  unitdir := GMacroList.ExpandMacro(unitdir);
  if not fpgDirectoryExists(unitdir) then
  begin
    {$IFDEF DEBUG}
    writeln('DEBUG:  TBuilderThread.Execute - Creating dir: ' + unitdir);
    {$ENDIF}
    fpgForceDirectories(unitDir);
  end;
  p := TProcess.Create(nil);
  p.Options := [poUsePipes, poStdErrToOutPut];
  p.ShowWindow := swoShowNormal;
  p.CurrentDirectory := GProject.ProjectDir;
  // build compilation string
  c := gINI.ReadString(cEnvironment, 'Compiler', '');
  c := c + GProject.GenerateCmdLine(False, BuildMode);
  c := GMacroList.ExpandMacro(c);
//  AddMessage('Compile command: ' + c);
  p.CommandLine := c;
  try
    p.Execute;
    { Now process the output }
    OutputLine:='';
    SetLength(Buf,BufSize);
    repeat
      if (p.Outputnil) then
      begin
        Count:=p.Output.Read(Buf[1],Length(Buf));
      end
      else
        Count:=0;
      LineStart:=1;
      i:=1;
      while i<=Count do
      begin
        if Buf[i] in [#10,#13] then
        begin
          OutputLine:=OutputLine+Copy(Buf,LineStart,i-LineStart);
          Synchronize(@DoOutputLine);
          OutputLine:='';
          if (i<Count) and (Buf[i+1] in [#10,#13]) and
(Buf[i]Buf[i+1]) then
            inc(i);
          LineStart:=i+1;
        end;
        inc(i);
      end;
      OutputLine:=Copy(Buf,LineStart,Count-LineStart+1);
    until Count=0;
    if OutputLine  '' then
      Synchronize(@DoOutputLine);
    p.WaitOnExit;
  finally
    FreeAndNil(p);
  end;
end;
=============================

Regards,
- Graeme -

2015-03-25 12:56 GMT+01:00 Graeme Geldenhuys :

Thanks Graeme, works well ... in Windows 7 here. Same code in Windows XP nothing to do. :O

Antonio

Are you sure that it is not specific to the executable that you run?

Did you try if redirecting the output of this executable to a file using simply Windows Console
executable.exe all args > outfile.txt

you get the same results on Windows XP as on Windows 7?

Pierre Muller

2015-03-25 17:15 GMT+01:00 Pierre Free Pascal :

aaargh !! Thank you Pierre, I did not try that.

I just watched at the console output. Redirecting the pipe shows command output on windows 7 output.txt and a blank output.txt in windows xp ! I will write to developer list, then !

Sorry to bother all you.

Antonio

Antonio Sanguigni wrote

Thanks Graeme, works well ... in Windows 7 here. Same code in Windows XP nothing to do. :O

I'm affair there must be something weird in your WinXP setup then. I just tested again using WinXP and Maximus IDE (which uses the exact code I posted earlier). Attached is a screenshot showing the compiler output in the Messages window - read from TProcess.

As I mentioned, that code works on Win2000 all the way to Win7 (and probably Win8 too), plus FreeBSD and Linux.

Regards,
- Graeme -

2015-03-25 17:26 GMT+01:00 Graeme Geldenhuys :

Sure Graeme, at this point I think you are right. I will try to get another windows XP box to test deeply.

Thank you
Antonio