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Re: tar deletes .exe files on extraction
----- Original Message -----
From: "Corinna Vinschen"
On Aug 8 03:16, Steven Hartland wrote:
If you extract a tar.gz file with an executable file and
an excitable file of the same name but with the .exe extension
on extract the .exe file is inexplicably deleted.
tar -xvzf test.tar.gz
Yeah, that's to be expected.
Cygwin always handled the .exe suffix transparently in terms of stat(2)
calls, but Cygwin 1.7 also handles them transparently in terms of
open(2) and any other call. Therefore, if a file foo.exe exists, and an
application calls stat("foo"), it will get told that, yes, "foo" exists.
That's a basic component of being able to call foo.exe from bash by just
typing foo<enter>. POSIX systems just don't have the .exe suffix for
AFAICS from the strace, tar unpacks mydir/myexe.exe, then it goes ahead
to unpack mydir/myexe. It tries to open the file with O_CREAT | O_EXCL
flags. Since the file exists from Cygwin's POV, open(2) returns -1 with
errno set to EEXIST. If that happens tar calls unlink("mydir/myexe")
and the unlink() call succeeds, since, as mentioned above, the .exe
suffix is transparent to every filesystem call. Therefore,
unlink("mydir/myexe") actually deletes "mydir/myexe.exe". Then tar
proceeds to unpack "mydir/myexe".
Keep in mind that myexe and myexe.exe are for all practical purposes the
same file from Cygwin's point of view. On a POSIX system you just don't
have a "normal" file called myexe in the same directory as an executable
"myexe", since that is the same file anyway, and the .exe suffix is just
an annoying Windowism. On Cygwin, you should avoid having a file "foo"
and a file "foo.exe" in the same directory at all cost to avoid
puzzeling POSIX borderline behaviour like this. What you do is
essentially in the "not supported" class of problems.
Fortunately for you there's a workaround. If the order of the files in
the tar archive is reversed, both files are unpacked. Or, unpack
mydir/myexe.exe explicitely afterwards. The reason that this works is
that Cygwin does not check for a file "foo", if the name of the file is
explicitely given as "foo.exe".
Thanks for the confirmation there Corinna however I do think this is quite
an issue and it likely catch people out.
In this example the result was nothing worked as the myexe is a none native
binary only myexe.exe is a windows exe, but I wouldnt be surprised if there
are cases where you have and exe and a data file with the name the same
just the app with the .exe with the extension.
It might be a silly idea but would it potentially be an option to alter
this behaviour based on an cygwin environment variable, so that the past
behaviour is restored for wider compatibility.
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