v2_prompt.sh

#!/bin/sh

TMP_DIR=".tmp"
mkdir -p $TMP_DIR

promptGCPEntry(){
    local _gcpIDCacheFilename="$TMP_DIR/gcpprojectid"

    if [ -e $_gcpIDCacheFilename ]; then
        gcpProjectId=`cat $_gcpIDCacheFilename`
        echo "You previously inputted GCP Project ID as \"$gcpProjectId\""
        
        while true; do
            read -p "Use the same project id? (Y/n): " _reuseCacheDecision
            case $_reuseCacheDecision in
                Y|y ) echo ""; return 0;;
                N|n ) break;;
                * ) echo "Please input a valid value.";;
            esac
        done
    fi

    while true; do
        read -p "Please input your Google Cloud Platform Project ID: " gcpProjectId
        case $gcpProjectId in
            "") echo "Please input a valid value.";;
            * ) echo $gcpProjectId > $_gcpIDCacheFilename; break;;
        esac
    done
    echo "You inputted GCP Project ID as \"$gcpProjectId\"\n"
}

promptGCPEntry

# Pretend this this doing something productive
echo "Running some commands for \"$gcpProjectId\"\n"
sleep 2