%tmp:~2,1%

从这里看到的，http://hi.baidu.com/allyesno/blog/item/b5f53e2c585dc832359bf748.html

稍微看了下，原来这个字符串是这个意思：%tmp:~2,1% = mid(%tmp%,2,1) = \

C:\Program Files>dir %tmp:~2,1%
 驱动器 C 中的卷没有标签。
 卷的序列号是 7407-D023

 C:\ 的目录

2008-09-11  10:38                96 AUTOEXEC.BAT
2007-01-30  13:38               192 bootbak.ini
2007-05-14  12:09    <DIR>          CCProxy
2007-03-28  01:10                 0 CONFIG.SYS
2008-10-10  11:41             6,204 debug.txt
2008-09-04  15:28    <DIR>          Documents and Settings
2007-04-09  09:49    <DIR>          Grub
2007-04-09  13:59    <DIR>          grub_for_dos-0.4.2
2008-10-15  12:57    <DIR>          Program Files
2006-08-24  15:22               552 project_template.bcp
2008-09-05  20:12               808 proxy.txt
2008-09-05  20:11               930 proxy.txt.bak
2008-10-09  16:12               600 PUTTY.RND
2008-10-16  14:09    <DIR>          WINDOWS
2007-01-30  13:46    <DIR>          wmpub
               8 个文件          9,382 字节
               7 个目录    363,540,480 可用字节

C:\Program Files>