Extract a string between two strings with bash

ExtractStringBetweenStrings.sh

#!/bin/bash

strindex() {
        x="${1%%$2*}"
        [[ "$x" = "$1" ]] && echo -1 || echo "${#x}"
}

function extractStringBetweenStrings() {
        # get parameters
        string="$1"
        stringBefore="$2"
        stringAfter="$3"

        # get lengths
        lengthOfStringBefore=${#stringBefore}
        lengthOfString=${#string}

        # get positions
        positionOfStringBefore=$( strindex "${string}" "${stringBefore}" )
        positionOfStringAfter=$( strindex "${string}" "${stringAfter}" )

        # cut from the end of stringBefore to the beginning of stringAfter
        cutPositionStart=$((${positionOfStringBefore} + ${lengthOfStringBefore} + 1))
        cutPositionEnd=${positionOfStringAfter}
        extractedString=$(echo ${string} | cut -c ${cutPositionStart}-${cutPositionEnd})

        # output extracted string
        echo "${extractedString}"
}

wholeStrings='<Test XML name="Test1234" revision="master" />'
extractStringBetweenStrings "${wholeStrings}" '<Test XML name="' '" revision="'