Shell Programming and Scripting

Hi I have the following in .kshrc file

set -o allexport
HOSTNAME=$(uname -n)
HISTSIZE=50
EDITOR=vi
ENV=$HOME/.kshrc
PATH=$HOME/bin:/usr/bin:/usr/local:/etc/bin/:/bin:/usr/local/bin:.
bind =complete
set +o allexport
clear

and I have the following in .profile

umask 077
MANPATH=$MANPATH:/usr/man:/usr/share/man:/usr/X11R6/man:/usr/local/man
#MANPATH=$MANPATH:/usr/local/lib/perl5/man
PS1="[muru:\w]"
alias mk="make -f demo_proc.mk build prob EXE=prob OBJS=prob.o"
alias ho="cd /store/store3/cse.pub/marty/cop6726"
#stty erase ^h
PATH=$PATH:/bin:/usr/local/bin:/usr/X11R6/bin:/usr/ucb:/usr/tools/magic-6.5/bin/
export PATH=/usr/local/j2sdk1.3/bin:.SERVLET.JAR:$PATH
alias d="dict"
LD_LIBRARY_PATH=/usr/X11R6/lib:/usr/openwin/lib:/usr/local/lib
#export PATH MANPATH PS1 LD_LIBRARY_PATH
TERM=ansi;export TERM
ENV=$HOME/.kshrc; export ENV

my default shell is /bin/bash that is displayed when I execute echo $SHELL

I go to ksh from my defaut shell and it displays the command promt as $ but when I execute echo $SHELL it still shows
/bin/bash.

cat /etc/shells shows the following
$ cat /etc/shells
/usr/bin/bash
/bin/tcsh
/bin/csh
/sbin/sh
/bin/sh
/bin/noshell
/usr/local/bin/bash
/bin/bash

Is it ok? I mean it should show /bin/ksh when u are in ksh right? or am I making a mistake?
Am I not in ksh? then why is the prompt in $ sign?

a few words of explanation would be greatly appreciated.

Thanks
Muru

use echo $0 to see which shell u currently in.

Thanks, it shows ksh.

When I try which ksh it shows /usr/bin/ksh.

Is not a must for the shell executable be in /etc/shells (i am probably wrong here) or since ksh is one of the available shells, doesn't this should be reflected in /ect/shells?

Thanks
Muru