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From: jerry@jvdsys.nextjk.stuyts.nl (Jerry van Dijk)
Subject: Re: Program (not task) Activation
Date: 1998/04/22
Message-ID: <Eru8pD.4E@jvdsys.nextjk.stuyts.nl>#1/1
X-Deja-AN: 347065160
References: <#CDmPrma9GA.300@ntawwabp.compuserve.com>
 <EACHUS.98Apr21125549@spectre.mitre.org>
 <6hjtju$kiq$1@owens.ridgecrest.ca.us>
Organization: * JerryWare *, Leiden, Holland
Newsgroups: comp.lang.ada
Date: 1998-04-22T00:00:00+00:00
List-Id: <comp.lang.ada>


Do-While Jones (do_while@ridgecrest.ca.us) wrote:

: Does anyone know why Windows 95 did not return an error code?

If you are using GNAT 3.10p on a Win95 machine, GNAT calls the system()
function from the MS RTS:

	int system( const char *command );

	If command is NULL and the command interpreter is found, the function
	returns a nonzero value. If the command interpreter is not found, it
	returns 0 and sets errno to ENOENT. If command is not NULL, system
	returns the value that is returned by the command interpreter. It
	returns the value 0 only if the command interpreter returns the value 0.
	A return value of - 1 indicates an error, and errno is set to one of the
	following values:

	E2BIG    Argument list (which is system-dependent) is too big.
	ENOENT   Command interpreter cannot be found.
	ENOEXEC  Command-interpreter file has invalid format and is not executable.
	ENOMEM   Not enough memory is available to execute command; or available
	         memory has been corrupted; or invalid block exists, indicating
	         that process making call was not allocated properly.

	You must explicitly flush (using fflush or _flushall) or close any
	stream before calling system.

Also, since you are using Ada95, why the difficult code. A portable way
to call system() in Ada95 could be:

-- demo.adb
with Commands; use Commands;

procedure Demo is
   Result : Integer;
begin
   Result := System_Command ("cat demo.adb");
end Demo;

-- Commands.ads
package Commands is

   function System_Command (Argument : String) return Integer;

end Commands;

-- Command.adb
with Interfaces.C; use Interfaces.C;

package body Commands is

   function System (S : char_array) return int;
   pragma Import (C, System, "system");

   function System_Command (Argument : String) return Integer is
   begin
      return Integer (System (To_C (Argument)));
   end System_Command;

end Commands;
-- 
-- Jerry van Dijk  | email: jdijk@acm.org
-- Leiden, Holland | member Team-Ada