[fpc-pascal]Using Tprocess to write to child process standard input.

[Michael Van Canneyt]

On Tue, 9 Mar 2004, Vincent Snijders wrote:

> Hi,
>
> I am having some problems writing to the InputStream of a Tprocess
> object. Below is the source code. I am testing this on windows. When
> stepping through the code I get INVALID_HANDLE as return value of the
> FileWrite in THandleStream.Write.
> I think there is a bug somewhere in the Tprocess code for win32, but
> before digging deeper I would like to know if anybody has succesfully
> used Tprocess like this on win32 platform.
>
> Regards,
> Vincent.
>
> The following procedure is from the parent application.
> procedure DoIt;
> var
>   LogProcess: TProcess;
>   procedure WriteLine(const s: string);
>   var
>     buffer: string;
>   begin
>     buffer := s + LineEnding;
>     LogProcess.Input.Write(buffer, Length(buffer));
>   end;

Eh ?? This should be

    LogProcess.Input.Write(buffer[1], Length(buffer));

Otherwise you will get some VERY strange things.

Secondly, in your logger app, you forget to do init, to open the file.

Michael.


> begin
>   LogProcess := TProcess.Create(nil);
>   LogProcess.Options := [poUsePipes];
>   LogProcess.CommandLine := 'logger.exe';
>   LogProcess.Execute;
>   WriteLine('test');
>   WriteLine('q');
>   LogProcess.WaitOnExit;
> end;
>
> The logger application is simply reads line from stdin and writes temp
> to a file, until the line 'q' is received. The source is this:
> program logger;
>
> {$mode objfpc}{$H+}
>
> uses
>   Classes;
>
> var
>   logfile: text;
>   line: string;
>
> procedure init;
> begin
>   assignfile(logfile, 'd:\troep\log.txt');
>   rewrite(logfile);
>   writeln(logfile, 'Started logging');
>   closefile(logfile);
> end;
>
> procedure AppendText(line: string);
> begin
>   append(logfile);
>   writeln(logfile, line);
>   closefile(logfile);
> end;
>
> begin
>   repeat
>     readln(line);
>     appendText(line);
>   until line='q';
> end.
>
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