Re: Exec shell command with GNAT

[Thomas Wolf <t_wolf@angelfire.com>]

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.)

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