Can we write our own shell??

Hello group,
Can anyone help me out by sharing some knowledge about how
to create our own shell?? Is it possible to write or create our own
shell?? Or can we modify shell to behave as per our need?

"bobby" <(E-Mail Removed)> writes:

> Can anyone help me out by sharing some knowledge about how
> to create our own shell??

You might want to be more specific as to what you want to know, and
what you already know.

A good place to start would probably be to figure out why you want to
write your own shell, and what it does differently from other shells.

I once wrote a shell (in C) for an assignment at university, so it is
actually possible ;-) It gave a good insight into how file descriptors
and such things work.

> Is it possible to write or create our own
> shell?? Or can we modify shell to behave as per our need?

Yes!

But why do you want to write your own shell?

--
Jacob

Thanx Jacob for the reply......
Actually i need a facility so that i can ENCRYPT the data
whatever is being transferred to any external device, which maintains
the security. Or rather appending some facilties in existing shells.
As per now i know how to use shell commands and what is shell and how
shell functions and why is it necessary. But never i came across to
modify the shell as such. Waiting for reply...


Thanx Jacob .....



Jacob Bunk Nielsen wrote:
> "bobby" <(E-Mail Removed)> writes:
>
> > Can anyone help me out by sharing some knowledge about how
> > to create our own shell??
>
> You might want to be more specific as to what you want to know, and
> what you already know.
>
> A good place to start would probably be to figure out why you want to
> write your own shell, and what it does differently from other shells.
>
> I once wrote a shell (in C) for an assignment at university, so it is
> actually possible ;-) It gave a good insight into how file descriptors
> and such things work.
>
> > Is it possible to write or create our own
> > shell?? Or can we modify shell to behave as per our need?
>
> Yes!
>
> But why do you want to write your own shell?
>
> --
> Jacob

"bobby" <(E-Mail Removed)> writes:

> Actually i need a facility so that i can ENCRYPT the data
> whatever is being transferred to any external device, which maintains
> the security.

In that case, I don't think you want to modify a shell. A shell is
basically just a program that is used to start other programs. These
could be anything, email programs, webbrowsers ...

These programs may send unencrypted information without the shell ever
knowing anything about it.

--
Jacob

"bobby" <(E-Mail Removed)> writes:

> Hello group,
> Can anyone help me out by sharing some knowledge about how
> to create our own shell?? Is it possible to write or create our own
> shell?? Or can we modify shell to behave as per our need?

Yes. It's a standard assignment in undergrad operating systems courses.
--
Joseph J. Pfeiffer, Jr., Ph.D. Phone -- (505) 646-1605
Department of Computer Science FAX -- (505) 646-1002
New Mexico State University http://www.cs.nmsu.edu/~pfeiffer

"bobby" <(E-Mail Removed)> writes:

> Thanx Jacob for the reply......
> Actually i need a facility so that i can ENCRYPT the data
> whatever is being transferred to any external device, which maintains
> the security. Or rather appending some facilties in existing shells.
> As per now i know how to use shell commands and what is shell and how
> shell functions and why is it necessary. But never i came across to
> modify the shell as such. Waiting for reply...

Why is using ssh not the answer?
--
Joseph J. Pfeiffer, Jr., Ph.D. Phone -- (505) 646-1605
Department of Computer Science FAX -- (505) 646-1002
New Mexico State University http://www.cs.nmsu.edu/~pfeiffer

On Thu, 09 Nov 2006 01:42:50 -0800, bobby wrote:

> Hello group,
> Can anyone help me out by sharing some knowledge about how
> to create our own shell?? Is it possible to write or create our own
> shell?? Or can we modify shell to behave as per our need?


a shell is a program that runs when the user logs in and is
authenticated. the /etc/passwd file has the shell that a
user will run. you can write your own foo shell that
does what you want and put that in the /etc/passwd file
for the user. when the user logs in, foo will be his
shell. it's up to you to do the input / output / commands
that a shell provides.

--
D.A.M. - Mothers Against Dyslexia

see http://www.jacksnodgrass.com for my contact info.

jack - Grapevine/Richardson