Re: Is there some way of calling a system command?

["jimmaureenrogers@worldnet.att.net" <jimmaureenrogers@worldnet.att.net>]

Aldebaran wrote:
> I am a newbie Ada-programmer and need help with this topic.
> In C one can launch a system command, for instance through
>  the following function.
>
>  system("ls ");
>
> or in JAVA
>
>  exec("ls");
>
> Is there some similar  way of calling a system command in ADA?

The easiest way is to simply call the C system command.
The example below was run on my Windows XP system.

with Interfaces.C.Strings;
use Interfaces.C.Strings;

procedure System_Example is
   function System_Call(Command : Chars_Ptr) return Interfaces.C.Int;
   pragma Import(Convention => C, Entity => System_Call,
      External_Name => "system");
   Rc : Interfaces.C.Int;

begin
   Rc := System_Call(New_String("dir"));

end System_Example;

The important part of the example is the creation of a function
specification I have named System_Call. That function specification
take a parameter of Chars_Ptr, which corresponds to a C char *.
The function specification is used as the Ada interface to the C
system call. The compiler is notified of that association through
the pragma Import. That pragma causes the compiler to link the C
system command and call it whenever System_Call is called in the
Ada code.

Jim Rogers