Can anyone explain the use of init3

[Kenneth Porter]

--On Wednesday, April 19, 2006 4:57 PM -0400 Tom Diehl 
<tdiehl at rogueind.com> wrote:

> On Wed, 19 Apr 2006, Kenneth Porter wrote:
>
>> On Wednesday, April 19, 2006 2:53 PM +0100 Chris Linton-Ford
>> <chris.lintonford at firebox.com> wrote:
>>
>> When your objective is to change the runlevel, you should invoke
>> telinit.  Future versions of the program may treat invocation as init to
>> do something  quite different.
>
> So do you know more about this then the man pg?
>
>> From the init man page:
>
> "The init binary checks if it is init or telinit by looking at its process
> id; the real init's process id is always 1.  From this it follows that
> instead of calling telinit one can also just use init instead as a
> shortcut."
>
> Notice the part about the shortcut??
>
> I have only been administering *nix systems for a short time (15 years)
> but in that time I can tell you I have never typed telinit except in
> response to statments like the above.

I have to wonder why telinit exists then. Did someone start using it in 
scripts so that it got grandfathered and every subsequent Unix-like OS had 
to keep a link to that name around? Or is the man page writer just making 
an observation about the implementation? The fact that it checks the 
process ID sounds like a defensive hack rather than a feature. It could 
also have checked the ID and refused to run if it was invoked as "init".