CMD: piping ECHO to SET/ expanding variables in variables

Question

%x:~12,3% Returns 3 characters starting at the 12:th character in x variable. What I have been trying to accomplish is using variables instead of 12 an

Answer 1

You need to enable delayed expansion.

@echo off
setlocal enabledelayedexpansion

set string=1234567890abcdef
set substring_start=12
set substring_length=3

set substring=!string:~%substring_start%, %substring_length%!
set command=echo !substring!

!command!
pause