[Foreigner]

bombording,
Узнать длину строки:

Код:

@echo off
setlocal

set "string=C:\some folder\some folder\some folder\some folder\file.ext"
:loop

set "string=%string:~0,-1%" && set /a len+=1
if defined string goto:loop

if %len% gtr 260 (echo wrong path length: %len%) else (echo Ok: %len%)