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# 1  
Old 10-02-2001
Question Shell Implementation

I want to implement my own simple multi tasking shell in Unix which will take care of redirection (<, >, >>) and piping.
I am just unable to get a concrete idea of how exactly I have to start. I have several books...some are..

1. Maurice Bach- Design Of Unix Operating System
2. Richard Stevens- Advanced Programming in Unix

However I find the language too high and complicated in these books.

Can someone please suggest how exactly I should go abt it...(step by step)

What are the things that I need to Learn to Implement this?
(anything and everything)


Smilie Smilie
# 2  
Old 10-02-2001
Based on the GREAT books you mention, I gather you
are thinking about using C... yes?

IMHO an excellent choice. However, if you are new to C,
those books may be more confusing than helpful.

I would suggest a "friendlier" book. There are so many
books out there I would be hard pressed to recommend
any particular one. You may want to search through the FAQs
on this forum for some book titles.

If C is not your cup of tea... you can also use perl.

Anyway, sounds like a great learning project and with those
books, you are on the right track. Smilie
# 3  
Old 10-02-2001
Thanks rwb1959.......but thats not what exactly that I wanted....
A more detailed guidance would be really helpful for me...
# 4  
Old 10-02-2001

In general, you want to write a program that take "line" input
(i.e. gets() ) and parses it looking for "special" characters
(don't forget to process escape "\" characters as well). From
that point, you can use fork() exec() to actually run the commands
and use popen() to facilitate redirection to/from parent and
children processes.

I hope this gives you an idea of where to start. Note that in
at least one C programming book (I don't remember which),
they actually give you a rudimentary shell as a programming
example.
 

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