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Subject: Re: HELP: PC System Call
References: <ZtcM8.49323$KD3.980836@typhoon.ne.ipsvc.net>
From: Jerry van Dijk <jvandyk@attglobal.net>
Date: 08 Jun 2002 09:59:36 +0200
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Date: 2002-06-08T09:59:36+02:00
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> In the past, the students used UNIX workstations, and I assigned them
> the GETENV problem from them book. You know, call the UNIX
> getenv function with an environment variable, and get the mapped
> results back. We used all the C interface libraries, and it work just
> like in the book!

Hmmmm, I can't find such an exercise in the book, only 19.7, asking a body
for a system call. Since you mentioned DLL's, I gather that you are running
Windows on the PC's. Although I do not understand what it is that does
not work, the following works fine with GNAT 3.14p for NT:

with Ada.Text_IO;          use Ada.Text_IO;
with Interfaces.C.Strings; use Interfaces.C.Strings;

procedure Check is

   function getenv (Name : chars_ptr) return chars_ptr;
   pragma Import (C, getenv, "getenv");

   function Get_Env (Name : String) return String is
      Result : chars_ptr;
      C_Name : chars_ptr := New_String (Name);
   begin
      Result := getenv (C_Name);
      Free (C_Name);
      return Value (Result);
   end Get_Env;

begin
   Put_Line ("COMSPEC = " & Get_Env ("COMSPEC"));
end Check;

-- 
--  Jerry van Dijk   | email: jvandyk@attglobal.net
--  Leiden, Holland  | web:   users.ncrvnet.nl/gmvdijk