Article View: comp.os.msdos.programmer
Article #2236"file cannot be copied onto itself"
From: Chuck Anderson
Date: Fri, 14 Sep 1990 21:39
Date: Fri, 14 Sep 1990 21:39
23 lines
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1612 bytes
Qvestion:
How does the DOS "copy" command know when the source and destination file are
one in the same (i.e., "file cannot be copied onto itself")? I can't believe
that it's just a string compare. The logistics of that are pretty awkward.
I have written my own "nice" copy command (in Turbo C) to prevent accidental
overwriting (destruction) of a file. The program works fine. It allows the
option of renaming the dest (if it exists), appending to it, overwriting it,
or canceling the copy operation.
Then I hit this stumbling block. How do you know if you are going to try to
write a file onto itself? This sounds simple, but seems rather complex to me
after trying a few things. You cannot *simply* compare the two names. That
involves a lot of analysis as to just how the files were specified on the
command line. There must be a better way.
How does one determine that two files are indeed the same physical file?
*************************************************************************
Chuck Anderson uucp : uunet!isis!nyx!cla
Boulder, Co. (303) 494-6278 internet: cla@nyx.cs.du.edu
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!uunet!isis!nyx!cla From: cla@nyx.UUCP (Chuck Anderson) Newsgroups: comp.os.msdos.programmer Subject: "file cannot be copied onto itself" Message-ID: <2091@nyx.UUCP> Date: 14 Sep 90 21:39:07 GMT Reply-To: cla@nyx.UUCP () Organization: Public Access Unix - University of Denver Lines: 23