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

[tolkamp <f.tolkamp@gmail.com>]

Op zondag 11 juni 2006 15:19:12 UTC+2 schreef jimmaure...@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

Thank you for your reaction.
For me this is not very understandable.
Where must I put the directory path to the executable?
Is this "dir" in  Rc := System_Call(New_String("dir"));?