Why .RAR file contains different files with the same name_问答_开发者

I got a .RAR file which contains different files with the same name.

For example,

index.txt 40 Text Document 04/01/2010 4:40PM
index.txt 22 Text Document 04/01/2010 4:42PM
index.txt 10 Text Document 04/01/2开发者_Python百科010 4:45PM
index.txt 13 Text Document 04/01/2010 4:50PM

Why?

Like said before, the files could be in separate paths, but as I'll show further, this isn't always the case.

If you use WinRAR to list the file contents and your options are set as the following, then it only appears you have files with the same name, but they are in different paths.

Options -> File list -> Flat folders view (ctrl+h)
Options -> File list -> Details

After the column CRC32, there is one called Path. If this is different, extraction shouldn't be a problem if:

Extract -> Extraction path and options -> Advanced -> Extract relative paths is set.

If it is Do not extract paths, WinRAR will need to ask you to rename them because of file system limitations. I assume command line unrar won't be a problem in this case because you need to specify additional parameters to change its default behavior.

It is possible for a RAR archive to have multiple files with the same name in the same directory. If you use Windows, use "C:\Program Files\WinRAR\Rar.exe" instead of rar on the command line in the following examples.

Create a new file and add it to a RAR archive. You can also check the changes by listing its contents.

rar a rarfile.rar testfile.txt
rar l rarfile.rar
rar a rarfile.rar testfile.txt

If you try to re-add this file, rar will replace the already added file with the same name.

Updating archive rarfile.rar

Updating  testfile.txt                                                     OK
Done

Create an other file or rename the first one and add it to the RAR file.

move testfile.txt second.txt            (new file)
rar a rarfile.rar second.txt            (add it)
rar lb rarfile.rar                      (list archive, bare info)

Rename the second file to the first one's name.

rar rn rarfile.rar second.txt testfile.txt

This is how you create a RAR file with multiple files of the same name in the same path. These steps will be similar in WinRAR. If you try to rename the file again, the file name of all files in that directory will change too.

Why would someone want to do this?

The only explanation I can think of is that the person that created this archive wanted to imitate a version control/backup system. But if you want to extract only one specific version and it isn't the first one, WinRAR extracts the wrong file. It seems I've found a very obscure WinRAR bug :-)

Edit: seems a bad explanation after finding this in the RAR documentation:

-ver[n] File version control

        Forces RAR to keep previous file versions when updating
        files in the already existing archive. Old versions are
        renamed to 'filename;n', where 'n' is the version number.

        By default, when unpacking an archive without the switch
        -ver, RAR extracts only the last added file version, the name
        of which does not include a numeric suffix. But if you specify
        a file name exactly, including a version, it will be also
        unpacked. For example, 'rar x arcname' will unpack only
        last versions, when 'rar x arcname file.txt;5' will unpack
        'file.txt;5', if it is present in the archive.

        If you specify -ver switch without a parameter when unpacking,
        RAR will extract all versions of all files that match
        the entered file mask. In this case a version number is
        not removed from unpacked file names. You may also extract
        a concrete file version specifying its number as -ver parameter.
        It will tell RAR to unpack only this version and remove
        a version number from file names. For example,
        'rar x -ver5 arcname' will unpack only 5th file versions.

        If you specify 'n' parameter when archiving, it will limit
        the maximum number of file versions stored in the archive.
        Old file versions exceeding this threshold will be removed.

they are in different paths, most likely.

try outputting the full path. or see what happens when you extract them.

you'll probably see something like: