#1519 Duplicate filenames on extraction - windows command-line version

[Mysteron347]

When a file with a long filename is extracted, it may create an alias 8.3 filename which matches a filename to be extracted later from the archive.

If the 8.3 filenames were extracted first and the long filenames extracted as a second phase, this problem could be averted.

[Shell]

8.3 filenames are created by OS, not by 7-Zip itself. Such names often look like FILENA~1.TXT, which almost always guarantees they will not match meaningful filenames. Do you have an example of the contrary?

It is possible to make 7-Zip delete the short name, but I think this matter should be handled by the OS.

[Anonymous]

facing exact same issue :(
fixed it :)
link

[Gauthier Van Vreckem]

https://support.microsoft.com/en-us/kb/121007
To disable 8.3 name creation on all NTFS partitions, type fsutil.exe behavior set disable8dot3 1 at an elevated command prompt, and then press Enter.

you can also disable it on a specific partition.

[Mysteron347]

Here's a batchfile I used for testing:

@ECHO OFF
SETLOCAL

:: U: is my RAMdrive

SET "destdir=U:\demo"
:: create the destination directory and empty it
MD "%destdir%" >NUL 2>NUL
DEL "%destdir%\?*?"
:: Temporarily switch to newly-created/cleared directory
:: generate 2 files
FOR /L %%a IN (1,1,2) DO (
 DIR >"%destdir%\demons~%%a.txt"
rem DIR >"%destdir%\delivery~%%a.txt"
)
DIR >"%destdir%\demonstrate1.txt"
DIR >"%destdir%\demonstration1.txt"
:: archive them
7z a "%destdir%\archive" "%destdir%\d*"
:: show directory
DIR /x %destdir%
:: delete the d* files
DEL "%destdir%\d*"
:: show directory
DIR /x %destdir%
:: un-archive.
::
:: The lfn file is extracted first and windows creates an sfn alias
:: which exactly matches the filename of the second file to be extracted.
::
pushd %destdir%
7z e "%destdir%\archive.7z"
::
:: Extracting the 8.3 filenames as a first pass and then the remaining files
:: as a second pass would prevent this from happening
::
:: show directory
DIR /x %destdir%
:: back to original directory
popd

GOTO :EOF

*** Notes: My U: drive is a 2Gb FAT Ramdrive.

*** This particular batch has never failed, but have found similar batches attempting to extract from an archive where a shortfilename is generated which matches the full filename of a filename to be extracted later in the archive.

Now here's an astounding preculiarity:

If I execute a series of commands from the prompt:

pushd u:\demo&del d*&7z e archive.7z&popd&dir /x u:\demo
pushd u:\demo&del d*&7z e "archive.7z"&popd&dir /x u:\demo
pushd u:\demo&del d*&7z e "u:\demo\archive.7z"&popd&dir /x u:\demo
pushd u:\demo&del d*&7z e u:\demo\archive.7z&popd&dir /x u:\demo
u:
cd \
(then the above sequence of 4 lines again)
cd \demo
(then the above sequence of 4 lines again)
del d*&7z e archive.7z&dir /x u:\demo
del d*&7z e "archive.7z"&dir /x u:\demo
del d*&7z e "u:\demo\archive.7z"&dir /x u:\demo
del d*&7z e u:\demo\archive.7z&dir /x u:\demo

Then it sometimes works - and sometimes fails, with no apparent pattern. I've tried different times-of-day, starting a fresh cmd.exe instance, having multiple cmd.exe instances and have been unable to discern a pattern.

Sadly, mr. kim's link above fails for me. I'm aware that "echo u|7z e archive.7z" will overcome the problem - but by auto-renaming the sfns. (I'd suggest a switch (-au?)) to control automatic-accept-renaming)

Perhaps

(Y)es / (N)o / (A)lways / (S)kip all / A(u)to rename all / (Q)uit?

could be extended to

(Y)es / (N)o / (A)lways / (S)kip all / A(u)to rename all / (Q)uit
(K)ey in new name / (R)eplace with autogeneratednewname ?

Where K would allow a new name to be keyed in from the keyboard and R would extract the file to a new name "autogeneratednewname" for this file only, unlike U which accepts the auto-geenrated new name for all clashing filenames.

[Shell]

Nobody argues that there is such a problem. The fact is that filenames like demons~1.txt do not usually appear in archives. In my opinion, this behavior with short names needs not to be fixed, at least in 7-Zip.

As for manual renaming, I think it might be a useful feature.