[fpc-pascal]popen problems...

[Michael Van Canneyt]

On Wed, 14 Aug 2002, Martyn Ranyard wrote:

>
> Hi all,
>
>    I am writing a menu program in FPC, gpl'd so I'm asking here for
> comments, as I don't quite understand why my calls are no longer working.
>
> Procedure ExecAndDisplay(Command: String);
> Var
>    TheFile : File;
>    Ch      : Char;
>    TheBuff : String;
>    EndOfFile : Boolean;
> Begin
>    EndOfFile := False;
>    popen(TheFile, Command, 'r');
>    Repeat
>      If not Eof(TheFile) then

You cannot do eof(thefile) on a binary file, because that one will
attempt to determine the position in the file. This is done using a
seek, and a seek on a pip is not legal.

The correct way to code this would be

Procedure ExecAndDisplay(Command: String);

Var
   TheFile : File;
   Ch      : Char;
   TheBuff : String;
   EndOfFile : Boolean;
   BytesRead : INteger;

Begin

   Repeat
     BlockRead(Thefile, Ch, 1,BytesRead)
     If BytesRead<>1 then
       begin
       // ...
       end
   Until (bytesread=0);


Michael.