Function to get index of needs element in array

index_of.sh

#!/bin/bash
function index_of() {
    index=0;
    for arg in ${@:2}; do
        index=$((index + 1))
        if [[ ${1} == ${arg} ]]; then
            echo ${index};
            break;
        fi
    done
}

echo $(index_of ${1} ${@:2})