I would appreciate Marcin's suggestion for ifconfig aswell.
A while ago, I looked at the source code of FreeBSD's ifconfig to
implement it for myself. It didn't looked too difficult.
It is something like:

 /* no arguments is equivalent to '-a' */
        if (!namesonly && argc < 1)
                all =3D 1;

Z.


2006/3/25, Jeremy C. Reed <reed@reedmedia.net>:
> On Fri, 24 Mar 2006, Garrett D'Amore wrote:
>
> > As far as ifconfig, ifconfig behaves that way (needing -a to show all
> > interfaces) on other operating systems as well.  For example, without
> > arguments, ifconfig on Solaris shows a help message, just as on NetBSD.
>
> Linux net-tools, FreeBSD, DragonFly, and OpenBSD versions of ifconfig
> print all interfaces with no arguments (-a is default).
>
>  Jeremy C. Reed
>
>