I'm trying to create a cron job that downloads the latest version of WhatsApp's APK from their website https://fmwhatdownload.pk/ using a bash script and make it available through my site.

So far, I'm able to obtain the version number from the site using the following (user-agent part omitted):

wget -q -O - "$@" whatsapp.com/android | grep -oP '(?<=Version )([\d.]+)'
And I can download the APK using the following command:

wget whatsapp.com/android/current/WhatsApp.apk
That part is fine. What I can't figure out is how to download the APK only if it's newer than the existing APK on the server. How should the script be?

Since I'm not a command-line pro, I guess there's a better way to achieve this than my current approach, so if you have any suggestions, I'd appreciate it very much.