VERIFY ON, COPY /V, XCOPY /V Commands Do Not Compare Data

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Some versions of the MS-DOS "User's Guide" and online Help indicate that the /V (verify) switch for the COPY and XCOPY commands actually compares the source and destination files to determine whether they are identical. This is not correct. The /V switch verifies that the destination file, once written, can be read. No comparison of the files occurs.

This information also applies to the VERIFY ON command.


When you use the VERIFY ON command, or the /V switch with the COPY or XCOPY command, the MS-DOS file system uses the block device driver command code function 09H, Write with Verify. This verification process consists of confirming that the data just written can be read (for example, that the data was not written to a bad sector on the disk). No comparison of the source and destination data occurs.

To compare the source and destination files, use the MS-DOS FC (file compare) command after you use the COPY or XCOPY command.


For more information about the VERIFY, COPY, XCOPY, or FC command, see your MS-DOS "User's Guide," or use the online Help in MS-DOS versions 5.0 and later.

"Advanced MS-DOS Programming," Ray Duncan, Microsoft Press, Chapter 14, pages 267-276


Article ID: 126457 - Last Review: May 6, 2003 - Revision: 2.0
  • Microsoft MS-DOS 3.1
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This article was written about products for which Microsoft no longer offers support. Therefore, this article is offered "as is" and will no longer be updated.

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