批處理變量替換和截取mac=mac~1,20是什么意思下面這段代碼，是獲取Mac地址的，有個東東看不懂，mac:-=!，mac:~1,20這幾個是什么意思？SUT_OS_Ver是一個記錄OS內核版本號變量，5.2是2003.

setlocal enableDelayedExpansion
echo.Get SUT MAC addresses:
for /f tokens=2 delims=: %%i in ('ipconfig /all ^|find Physical') do (
set mac=%%i
set mac=!mac:-=!
set mac=!mac:~1,20!
set MacIsRight=!mac:~12,2!
if not defined MacIsRight (
echo.MAC:!mac!
echo MAC:!mac!>>%WOL_Files_Path%%SUT_Info_File_Name%
)
IF %SUT_OS_Ver% == 5.2 (
set mac=!mac:~0,12!
echo.MAC:!mac!
echo MAC:!mac!>>%WOL_Files_Path%%SUT_Info_File_Name%
)
)
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