[SOLVED] How to detect array start index by current shells (zsh/bash)?

Issue

We all know arrays in Bash are indexed from zero, and in zsh are indexed from one.

How can the script know it should use 0 or 1 if I can't ensure the running environment is bash, zsh or something else?

Expected code sample:

#!/bin/sh

detect_array_start_index(){
  # ... how?
  echo 1
}
ARR=(ele1 ele2)
startIndex=$(detect_array_start_index) # 0 or 1
for (( i=${startIndex}; i < ${#ARR[@]} + $startIndex; i++ )); do
    echo "$i is ${ARR[$i]}"
done

I have a idea is find the index of the first value in a fixed array, I got this: Get the index of a value in a Bash array, but the accepted answer use bash variable indirection syntax ${!VAR[@]}, which is invalid in zsh.

Solution

Check the index 1 element of a two element array:

detect_array_start_index() {
  local x=(1 0)                                                   
  echo ${x[1]}
}

Answered By - okapi

Answer Checked By - Candace Johnson (WPSolving Volunteer)