Shell Programming and Scripting

Hello,
My team and I planing to create a new shell. We are including features like handing the "command not found" exception, etc....

1)Can you please give some suggestions on what do do while writing a new shell.....

2)can you please give me your problems with the existing shells..My platform is RED HAT 9 and FEDORA 8.

please list them out in points so that we can understand better......

First, a good shell should be cross-platform, so making this a Linux-specific question is a bad idea. Would you like me to move the post to another forum?

Second, it should be backwards-compatible with classic sh. It should also be POSIX compatible, but have extensions that remove POSIX stupidities.

Third, it should be better about quoting and handling spaces. Maybe it could be more perl- or php-like in this regard. Syntax for handling regexps would also be nice. A shell that can also be used as an ad-hoc web form language would be nice. (It doesn't need to replace PHP, only borrow basic ideas from it).

Third, what do you mean "handling" the "command not found" exception? Do you want to simply remove the PATH limitation so that if a program isn't in your PATH, the shell will find it anyway? Might be a good way to sneak in trojans! Maybe the shell could suggest alternative programs from a list of paths in the update/location database? Or it could use mod apache's speling.o module to find command-line typos?

Finally, have you looked into creating a zsh module? It already does many of these. I've read that zsh is remarkably modular and can be used to extend new features. I don't use it simply because I know bash pretty well and don't see a reason to change. If I were to start anew, I'd use zsh.

hello,
thanks a lot for your reply.It was very informative.I shall surely take your words and do the best that I can.
Can you please forward this post in other forums.You said you will do it.Can you send me the link.I shall go and keep seeing there.

I wanted to know the POSIX stupidities that you were saying.What are the problems we generally face with "POSIX"

I don't think that another shell is a good idea. I believe that the strength of the UNIX os is among other things its simplicity. After almost 30 years there is a dozen of shells and this is no good for anybody. Of course some new shells, e.g. bash are better than the older ones but you must have something very important to offer with another new shell. Thanks for hearing my opinion.

Dozens of shells have come and gone on UNIX and GNU/Linux over the years. Nothing wrong with producing a new shell. If it is exceptional, users will flock to it. If it is mundane, users will ignore it.

Some ideas. Make it object orientated. Look at what Dave Korn is doing with ksh93 and compound variables and types. Not quite there yet but heading in the right direction. Add methods to variables similar to what is called discipline functions in ksh93 but cleanly implemented. Look at Ruby for ideas in this area. Make it modular ALA zsh. Include auditing. Maybe profiling like on Solaris. Include native threads for job control and concurrency. Include extended regular expressions. Include date and time manipulation ALA ksh93 printf %T but using a different syntax.

Hello sir,
I am very happy to see the optimistic note of the posts above.I have finished handling the "command not found" exception. I am currently working on "help me linux".
Here my target is the linux newbie who know nothing abt commands.He can enter his doubts like = "how to list a file?" And my perl code will tell him about "ls". I also want to handle queries like "how to lst a file?".Here the spelling is wrong, even then I am working with commands like aspell,hunspell to do the job for me.

I also have ideas like encrypting files,derectories with gpg so that even if one could get root password, he cannot open it, searching in LAN using openSSH. Can you please tell me where I stand now.I dont know whether I am going in the right direction or not !!!