追加环境变量到Path

 @echo off
 setlocal enabledelayedexpansion 

 ::使用方法：
 :: "C:\WINDOWS"
 :: "C:\jar"
 SET x="C:\jar"
 Call :InPath %x%
 goto :eof

 :InPath
 SET LocalPathCopy=%PATH%
 :: whether exist %x%
 IF "%LocalPathCopy%" == "" GOTO OVER
 GOTO WHILE

 :: iterate path variable and check if the first parameter of InPath exists
 :WHILE
 FOR /f "delims=; tokens=1,*" %%I IN ("%LocalPathCopy%") DO (
   set LocalPathCopy=%%J
   ::echo "%%~I" == "%1" --------- "%LocalPathCopy%"
   IF /I "%%~I" == %1 (
     SET Result=1
     SET x=%%~I
     echo %x% exists
     GOTO OVER
   )
   GOTO WHILE
 )

 :: remove "
 SET x=%x:"=%

 IF "!Result!" == "" (
     echo "%x%" dont exists so we'll add it to path
     :: you can use SETX command correctly if it exists
     :: because the max length of your environment variable cant be great than 1024
     :: SETX PATH "%Path%;%x%"
     SET "Path=%Path%;%x%"
     echo !PATH!
     GOTO OVER
 )

 pause.

 :OVER
 PAUSE & GOTO :EOF