Increase or decrase Volume via Http API?

Does anybody know how to increase or decerase volume by step via api?
If I use http://beosound2300.local:3001/roonAPI/change_volume?volume=20&outputId=170103394b4dd26c4842b8197e22a1e0dd9b it set volume to 20, wich is work perfectly, so i decide to write linux script and change 20 to variable $VOLUME so command look: curl ‘http://beosound2300.local:3001/roonAPI/change_volume?volume=$VOLUME&outputId=170103394b4dd26c4842b8197e22a1e0dd9b
but nothing is happen. How I correctly put variable into curl command?
Or maybe should I use another command or method?

Hi @Zarko_Vargovic

Try using double quote instead of single quote (as far as I know single quote does not do variables).

Here’s my working bash script

#!/bin/sh

MY_VOLUME=10
echo $MY_VOLUME

curl "http://localhost:3001/roonApi/change_volume?outputId=1701aa4e166fe64eae164bfae7c5e928181e&volume=$MY_VOLUME"

Hope this helps