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DOS疑难解答 & 问题讨论（解答室） » (Solved) How to get the drive letter of a USB flash drive in a DOS batch file?

Floor1　chenqiguang	Posted 2006-12-26 23:13
初级用户　Posts 10　Credits 22
After booting a DOS boot disk made from a USB flash drive into MS-DOS7.1, on some machines its drive letter is “A:”, while on other machines its drive letter is “C:”. In the batch file autoexec.bat on the USB flash drive, when the drive letter of the USB flash drive is “A:”, program A needs to be executed; when the drive letter of the USB flash drive is “C:”, program C needs to be executed. How can I get the drive letter of the USB flash drive in the DOS batch file autoexec.bat to make this work? Thanks in advance! Solved using the method introduced in post #4. Thanks again for the answers from the helpful members! [ Last edited by chenqiguang on 2006-12-27 at 10:28 PM ]

Floor2　zplinux	Posted 2006-12-26 23:53
新手上路　Posts 4　Credits 7　From 四川成都
I can't answer the OP's question. But I can provide one method I use for reference: In “autoexec.bat”, set the program execution path like this: SET PATH=A:\dos_tool\;A:\;\C:\dos_tool\;C:\ After that, when executing a program, just write the program name directly. For example: LH CTMOUSE LH DOSKEY There is no need to call the program with an absolute path. That will do. As for the reason for the difference between A and C drives, it is related to the way the bootable USB flash drive is made. With the zip/FDD method, after booting it becomes drive A With the HDD method, after booting it becomes drive C. If anything is incomplete, you can contact me by E-mail for discussion. zplinux@21cn.com

Floor3　chenqiguang	Posted 2006-12-27 00:22
初级用户　Posts 10　Credits 22
The program to be executed needs parameters, so an absolute path must be used.

Floor4　lianjiang2004	Posted 2006-12-27 03:48
金牌会员　Posts 1,884　Credits 3,946
You can put a signature file in the root directory of your USB flash drive and use it for detection. Suppose the file is myudisk.000 if not exit a:\myudisk.000 goto c a goro exit :c c :exit [ Last edited by lianjiang2004 on 2006-12-27 at 03:50 AM ]

Floor5　chenqiguang	Posted 2006-12-27 05:09
初级用户　Posts 10　Credits 22
Originally posted by lianjiang2004 at 2006-12-27 03:48: You can put a signature file in the root directory of your USB flash drive and use it for detection. Suppose the file is myudisk.000 if not exit a:\myudisk.000 goto c a goro exit :c c :exit [ Last edited by lianjiang2004 ... I'll reply again after testing it.

Floor6　zihan	Posted 2006-12-30 00:18
初级用户　Posts 24　Credits 66
This problem is very simple. I also ran into it when making a bootable USB flash drive. The USB flash drive was originally ZIP, but some motherboards insist on recognizing it as drive C: after booting, so the drive letter of the boot disk has to be identified. There are two methods: 1. Signature detection, FOR %%A IN (A: C:) DO IF EXIST DOS\DRIVERS\NUL SET BDR=%%A （DOS\DRIVERS is a directory on my USB flash drive）This way the boot drive letter can be set into the %BDR% variable. 2. Use a small tool: bootdrv.com. After running it, it will return an errorrlevel value, and by testing that you can know the boot drive letter.