How to use case statements in bash by its index value? - bash

Question

I have the following code where the user picks a file type, then I run certain code for each case:
#!/bin/bash
PS3='Please enter your file type choice: '
options=(".c (C)" \
".cpp (C++)" \
".css (CSS)" \
".html (HTML)" \
".java (Java)" \
".ms (Groff)")
select option in "${options[#]}" # Asks for the option choice
do
case "${option}" in
".c (C)") # C programming file
echo "C OPTION SELECTED"
;;
".cpp (C++)") # C++ programming file
echo "C++ OPTION SELECTED"
;;
".css (CSS)") # CSS programming file
echo "CSS OPTION SELECTED"
;;
".html (HTML)") # HTML File
echo "HTML OPTION SELECTED"
;;
".java (Java)") # Java programming file
echo "JAVA OPTION SELECTED"
;;
".ms (Groff)") # Groff markup file
echo "GROFF OPTION SELECTED"
;;
*) echo "invalid option $option"
;;
esac
done
I was wondering how I can make it like this, where in the case statement you can address each case by the index of the array instead of the value of the array:
#!/bin/bash
PS3='Please enter your file type choice: '
options=(".c (C)" \
".cpp (C++)" \
".css (CSS)" \
".html (HTML)" \
".java (Java)" \
".ms (Groff)")
select option in "${options[#]}" # Asks for the option choice
do
case "${option}" in
1) # C programming file
echo "C OPTION SELECTED"
;;
2) # C++ programming file
echo "C++ OPTION SELECTED"
;;
3) # CSS programming file
echo "CSS OPTION SELECTED"
;;
4) # HTML File
echo "HTML OPTION SELECTED"
;;
5) # Java programming file
echo "JAVA OPTION SELECTED"
;;
6) # Groff markup file
echo "GROFF OPTION SELECTED"
;;
*) echo "invalid option $option"
;;
esac
done
I did a lot of research and I'm not the best at bash (but I'm learning). Sorry if the solution is obvious but I would appreciate your help, that you.

Answer 1

On bash 4.0 or newer, you can build a reverse index as an associative array:
declare -A options_reverse=()
for idx in "${!options[#]}"; do
val=${options[$idx]}
options_reverse[$val]=$idx
done
...after doing which, ${options_reverse[$option]} will map to the desired index.
Combined with the rest of your program, this would look like:
#!/bin/bash
case $BASH_VERSION in ''|[0-3].*) echo "ERROR: Bash 4.0+ required" >&2; exit 1;; esac
PS3='Please enter your file type choice: '
options=(
".c (C)"
".cpp (C++)"
".css (CSS)"
".html (HTML)"
".java (Java)"
".ms (Groff)"
)
declare -A options_reverse=()
for idx in "${!options[#]}"; do
val=${options[$idx]}
options_reverse[$val]=$idx
done
select option in "${options[#]}"; do
case "${options_reverse[$option]}" in
0) echo "C OPTION SELECTED";;
1) echo "C++ OPTION SELECTED";;
2) echo "CSS OPTION SELECTED";;
3) echo "HTML OPTION SELECTED";;
4) echo "JAVA OPTION SELECTED";;
5) echo "GROFF OPTION SELECTED";;
*) echo "invalid option $option";;
esac
done

Answer 2

From help option:
The line read is saved in the variable REPLY.