貌似没有很优美的做法，只能把%Path%按分号分割，然后一段一段地比较。
:InPath [In]Path [Out]0/1
SETLOCAL
SET LocalPathCopy=%PATH%
SET Result=0
:WHILE
IF "%LocalPathCopy" == "" GOTO WEND
FOR /F "delims=;" %%I IN ("%LocalPathCopy%") DO (
IF /I "%%~I" == "%~1" (
SET Result=1
GOTO WEND
)
)
FOR /F "delims=; tokens=1,*" %%I IN ("%LocalPathCopy%") DO (
SET LocalPathCopy=%%~J
)
GOTO WHILE
:WEND
:InPathRet
ENDLOCAL & SET %2=%Result% & GOTO :EOF
使用方法：
SET x=C:\Windows Call :InPath %x% Result IF %Result% == 0 SET Path=%Path%;%x%
原文：http://www.jb51.net/article/67635.htm