Beyond Linux® From Scratch - Version svn-20070421

Chapter 11. System Utilities

UnZip-5.52

Introduction to UnZip

The UnZip package contains ZIP extraction utilities. These are useful for extracting files from ZIP archives. ZIP archives are created with PKZIP or Info-ZIP utilities, primarily in a DOS environment.

[Caution]

Caution

The UnZip package has some locale related issues. See the discussion below in the section called “UnZip Locale Issues”. A more general discussion of these problems can be found in the Program Assumes Encoding section of the Locale Related Issues page.

Package Information

Additional Downloads

User Notes: http://wiki.linuxfromscratch.org/blfs/wiki/unzip

UnZip Locale Issues

[Note]

Note

Use of UnZip in the JDK, Mozilla, DocBook or any other BLFS package installation is not a problem, as BLFS instructions never use UnZip to extract a file with non-ASCII characters in the file's name.

The UnZip package assumes that filenames stored in the ZIP archives created on non-Unix systems are encoded in CP850, and that they should be converted to ISO-8859-1 when writing files onto the filesystem. Such assumptions are not always valid. In fact, inside the ZIP archive, filenames are encoded in the DOS codepage that is in use in the relevant country, and the filenames on disk should be in the locale encoding. In MS Windows, the OemToChar() C function (from User32.DLL) does the correct conversion (which is indeed the conversion from CP850 to a superset of ISO-8859-1 if MS Windows is set up to use the US English language), but there is no equivalent in Linux.

When using unzip to unpack a ZIP archive containing non-ASCII filenames, the filenames are damaged because unzip uses improper conversion when any of its encoding assumptions are incorrect. For example, in the ru_RU.KOI8-R locale, conversion of filenames from CP866 to KOI8-R is required, but conversion from CP850 to ISO-8859-1 is done, which produces filenames consisting of undecipherable characters instead of words (the closest equivalent understandable example for English-only users is rot13). There are several ways around this limitation:

1) For unpacking ZIP archives with filenames containing non-ASCII characters, use WinZip while running the Wine Windows emulator.

2) After running unzip, fix the damage made to the filenames using the convmv tool (http://j3e.de/linux/convmv/). The following is an example for the ru_RU.KOI8-R locale:

Step 1. Undo the conversion done by unzip: 

convmv -f iso-8859-1 -t cp850 -r --nosmart --notest \
    </path/to/unzipped/files>

Step 2. Do the correct conversion instead: 

convmv -f cp866 -t koi8-r -r --nosmart --notest \
    </path/to/unzipped/files>

3) Apply this patch to unzip: https://bugzilla.altlinux.ru/attachment.cgi?id=532. It will apply with some offsets.

It allows to specify the assumed filename encoding in the ZIP archive using the -O charset_name option and the on-disk filename encoding using the -I charset_name option. Defaults: the on-disk filename encoding is the locale encoding, the encoding inside the ZIP archive is guessed according to the builtin table based on the locale encoding. For US English users, this still means that unzip converts from CP850 to ISO-8859-1 by default.

Caveat: this method works only with 8-bit locale encodings, not with UTF-8. Attempting to use a patched unzip in UTF-8 locales may result in a segmentation fault and is probably a security risk.

Installation of UnZip

Note that if you applied the patch described above for locale issues, the required security patch will have some offsets. Now install UnZip by running the following commands: 

patch -Np1 -i ../unzip-5.52-security_fix-1.patch &&
make -f unix/Makefile LOCAL_UNZIP=-D_FILE_OFFSET_BITS=64 linux

To test the results, issue: make check.

Now, as the root user: 

make prefix=/usr install

Command Explanations

linux: This target in the Makefile makes assumptions that are useful for a Linux system when compiling the executables. To obtain alternatives to this target, use make list

LOCAL_UNZIP=...: This sets the compilation flags to allow UnZip to handle files up to 4 GB.

Contents

Installed Programs: funzip, unzip, unzipfsx, zipgrep, and zipinfo
Installed Libraries: None
Installed Directories: None

Short Descriptions

funzip

allows the output of unzip commands to be redirected.

unzip

lists, tests or extracts files from a ZIP archive.

unzipfsx

is a self-extracting stub that can be prepended to a ZIP archive. Files in this format allow the recipient to decompress the archive without installing UnZip.

zipgrep

searches files in a ZIP archive for lines matching a pattern.

zipinfo

produces technical information about the files in a ZIP archive, including file access permissions, encryption status, type of compression, etc.

libunzip.so

contains the API functions required by the UnZip programs.

Last updated on 2007-04-04 21:42:53 +0200