Bash variables expansion (possible use of eval) in for-do loop - bash

Question

I am studying the book "Beginning Linux Programming 4th ed" and chapter 2 is about shell programming. I was impressed by the example on page 53, and tried to develop a script to display more on that. Here is my code:
enter code here
#!/bin/bash
var1=10
var2=20
var3=30
var4=40
for i in 1 2 3 4 # This works as intended!
do
x=var$i
y=$(($x))
echo $x = $y # But we can avoid declaring extra parameters x and y, see next line
printf " %s \n" "var$i = $(($x))"
done
for j in 1 2 3 4 #This has problems!
do
psword=PS$j
#eval psval='$'PS$i # Produces the same output as the next line
eval psval='$'$psword
echo '$'$psword = $psval
#echo "\$$psword = $psval" #The same as previous line
#echo $(eval '$'PS${i}) #Futile attempts
#echo PS$i = $(($PS${i}))
#echo PS$i = $(($PS{i}))
done
#I can not make it work as I want : the output I expect is
#PS1 = \[\e]0;\u#\h: \w\a\]${debian_chroot:+($debian_chroot)}\u#\h:\w\$
#PS2 = >
#PS3 =
#PS4 = +
How can I get the intended output? When I run it as it is I only get
PS1 =
PS2 =
PS3 =
PS4 = +
What happened with PS1 and PS2 ?
Why do not I get the same value that I get with
echo $PS1
echo $PS2
echo $PS3
echo $PS4
because that was what I am trying to get.

Answer 1

Shell running a script is always non interactive shell. You may force to run the script in interactive mode using '-i' option:
Try to change:
#!/bin/bash
to:
#!/bin/bash -i
see INVOCATION section in 'man bash' (bash.bashrc is where your PS1 is defined):
When an interactive shell that is not a login shell is started, bash reads and executes commands from
/etc/bash.bashrc and ~/.bashrc, if these files exist. This may be inhibited by using the --norc option. The
--rcfile file option will force bash to read and execute commands from file instead of /etc/bash.bashrc and
~/.bashrc.
When bash is started non-interactively, to run a shell script, for example, it looks for the variable BASH_ENV in
the environment, expands its value if it appears there, and uses the expanded value as the name of a file to read
and execute. Bash behaves as if the following command were executed:
if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi
but the value of the PATH variable is not used to search for the file name.
you can also read: http://tldp.org/LDP/abs/html/intandnonint.html
simple test:
$ cat > test.sh
echo "PS1: $PS1"
$ ./test.sh
PS1:
$ cat > test.sh
#!/bin/bash -i
echo "PS1: $PS1"
$ ./test.sh
PS1: ${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u#\h\[\033[01;34m\] \w \$\[\033[00m\]

Answer 2

Use indirect expansion:
for j in 0 1 2 3 4; do
psword="PS$j"
echo "$psword = ${!psword}"
done