Re: Exec shell command with GNAT

["David C. Hoos, Sr." <david.c.hoos.sr@ada95.com>]

----- Original Message ----- 
From: "Thomas Wolf" <t_wolf@angelfire.com>
Newsgroups: comp.lang.ada
To: <comp.lang.ada@ada.eu.org>
Sent: January 14, 2003 2:58 AM
Subject: Re: Exec shell command with GNAT


> david.c.hoos.sr@ada95.com wrote:
> > with Ada.Characters.Latin_1;
> > with System;
> > function Execute_Shell_Command
> >   (The_Command : String) return Integer is
> > 
> >    function Execute
> >               (The_Command_Address : System.Address) return Integer;
> >    pragma Import (C, Execute, "system");
> >    The_Nul_Terminated_Command_String : constant String :=
> >      The_Command & Ada.Characters.Latin_1.Nul;
> > begin
> >    return Execute (The_Nul_Terminated_Command_String'Address);
> > end Execute_Shell_Command;
> 
> Yes, that's it. My own version looks similar:
> 
>    with Interfaces.C;
> 
>    function Execute (Command : in String) return Integer
>    is
> 
>      function Run (Command : in Interfaces.C.char_array) 
>         return Interfaces.C.int;
>      pragma Import (C, Run, "system");
> 
>    begin --  Execute
>       return Integer (Run (Interfaces.C.To_C (Item => Command)));
>    end Execute;
> 
> No fiddling around with addresses needed, and the declaration of "Run"
> doesn't depend on Interfaces.C.int and Integer being the same. Note
> that the Ada standard guarantees that an in-parameter of an array of
> some element_type is passed in a way compatible with an "element_type *"
> in C. (I.e., the address of the first element is passed.)

I agree.  I failed to mention that my function was originally written
before Ada95 existed.  It's a case of "if it's not broken, don't 'fix'
it."

> 
> -- 
> -----------------------------------------------------------------
> Thomas Wolf                          e-mail: t_wolf@angelfire.com
> 
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