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From: Andi Kleen <ak@muc.de>
Subject: Re: [Q] Operating System Command Interface
Date: 1998/05/05
Message-ID: <m33eeoirv4.fsf@fred.muc.de>#1/1
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References: <6ims5j$1vo@gcsin3.geccs.gecm.com> <354F2EF4.41C6@hso.link.com>
Organization: [posted via] Leibniz-Rechenzentrum, Muenchen (Germany)
Newsgroups: comp.lang.ada
Date: 1998-05-05T00:00:00+00:00
List-Id: <comp.lang.ada>


"Stanley R. Allen" <s_allen@hso.link.com> writes:

> John McCabe wrote:
> > 
> > Am I right in thinking that, as standard, Ada has no direct perating
> > system command interface akin to the C "System" call?
> > 
> 
> My understanding is that the "system" call you are making
> in C is actually a call to the Unix operating system; it's
> not part of the C language.  The same kind of call can be made
> from Ada using pragma Interface (Ada 83) or pragma Import
> (Ada 95).

system() is part of the c library and not a system call on Unix.
It is implemented with fork() and exec(). It is part of the libc on
Unix systems and indeed part of the ISO Standard C library definition - 
so if you assume that the Ada C interface interfaces you to a full(1) 
ISO C it should be there.

Of course that doesn't mean that it is portable. What is done with
the string is implementation specified - just returning an error is legal.

-Andi

(1) Full - not subsetted. ISO C allows C without library for
embedded implementations.