🚀 go-pugleaf

In <4j6lv1$k3r@news.mpd.tandem.com> Joseph Crowe <jcrowe> writes:

>danpop@mail.cern.ch (Dan Pop) wrote:
>>Can you use a Unix system without a shell?  Try to remove all the shells
>>from your Unix system and see what you get :-)
>
>   Absolutely.  You could have a user login on a *NIX system and in the
>/etc/passwd entry for that user, have whatever binary you wish to provide the
>user interface.  That could include a totally graphical interface if one so
>desired.

Your Unix system won't even boot without a shell!  Just remove all the
shells, as I suggested and see if you can use that box, no matter what
you put in /etc/passwd as the user login shell.

The shells (or at least /bin/sh) are part of the design of a Unix system.
Library calls like system() and popen() or system components like cron
rely on the existence of /bin/sh and simply don't work without it.

>>BTW, you found no contradiction:  Will Packard is perfectly right, Unix
>>is not one or more shells, for the simple reason that the shells are a
>>component of the Unix system.  The other components are the kernel and
>>the system utilities.  All these components define a Unix system.
>
>   Shells in *NIX are applications, pure and simple.  

True, but irrelevant.  Everything in Unix is an application.  Some of them,
(e.g. /bin/sh, getty, login, init, ifconfig) are critical components of 
the operating system.

>They are forked from the
>login process based on the entry in /etc/passwd for whatever user is logging
>in. 

You don't have too many clues about Unix, do you?  There are tens if not
hundreds of shell processes started during the booting procedure, before
the first login prompt is even displayed.  After the kernel has been 
loaded and the init process has been started, everything else is done
by shell scripts.

>In many installations, certain logins will cause the fork()ing and
>exec()ing of some sort of window oriented application.  The *NIX OS is
>basically the kernel and system call interfaces, plus perhaps, libraries.  Not
>that this has a whole lot of relevence.

Plain bullshit.  Remove all the system utilities from /bin /usr/bin /sbin
/usr/sbin, etc and see what you can do on that Unix system.  After all,
you still have the kernel and the libraries.

>>The shell is to Unix what the finder is to MacOS.
>
>   Actually, that analogy only works halfway.  finder is more like fork/exec
>for MacOS, or perhaps init. 

The Unix shells and the MacOS finder are the primary user interfaces of
the respective systems.

Dan
--
Dan Pop
CERN, CN Division
Email: danpop@mail.cern.ch 
Mail:  CERN - PPE, Bat. 31 R-004, CH-1211 Geneve 23, Switzerland