shell

[ACMFIU]

Sorry for the vague title but:

I'm working on a UNIX shell for the Apple IIgs computer and am currently doing
the command-line editing features. I read here before that POSIX was
doing something with a shell (can't remember what). Anyway, is it worthwhile
me making this a POSIX conformant shell or emulating something like
csh, sh, tcsh, etc. Right now it's set to emulate sh. Also, is there some
shell that has emacs-like editing facilities. If so, where can I get a
description of these?

albert