7-Zip

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7-Zip
7ziplogo.svg
7-Zip.png
7-Zip File Manager on Windows 10
Developer(s) Igor Pavlov
Initial release 18 July 1999; 24 years ago (1999-07-18)[1]
Stable release 16.02 (May 21, 2016; 7 years ago (2016-05-21)) [±][1]
Written in C++[citation needed]
Operating system Windows, Linux, OS X
Size 1.3 MB
Available in 79 languages[citation needed]
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List of languages
Brazilian Portuguese, Czech, English, French, German, Italian, Japanese, Polish, Russian, Simplified Chinese, Sinhala, Spanish and Korean
Type File archiver
License GNU LGPLv2.1+ with unRAR restriction[2]
Website {{#property:P856}}

7-Zip is an open-source file archiver, an application used primarily to compress files. 7-Zip uses its own 7z archive format, but can read and write several other archive formats. The program can be used from a command-line interface, graphical user interface, or with a window-based shell integration. 7-Zip began in 1999[1] and is developed by Igor Pavlov. The cross-platform version of the command-line utility, p7zip, is also available.[3]

7-Zip is open-source software. Most of the source code is under the GNU LGPL license. The unRAR code is under the GNU LGPL with an "unRAR restriction", which states that developers are not permitted to use the code to reverse-engineer the RAR compression algorithm.[4][5]

Formats

7z

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Main article: 7z (file format)

By default, 7-Zip creates 7z-format archives with a .7z file extension. Each archive can contain multiple directories and files. As a container format, security or size reduction are achieved using a stacked combination of filters. These can consist of pre-processors, compression algorithms, and encryption filters.

The core 7z compression uses a variety of algorithms, the most common of which are bzip2, PPMd, LZMA2, and LZMA. Developed by Pavlov, LZMA is a relatively new system, making its debut as part of the 7z format. LZMA uses an LZ-based sliding dictionary of up to 4 GB in size, backed by a range coder.[6]

The native 7z file format is open and modular. All filenames are stored as Unicode.[7]

TopTenReviews found that the 7z compression is at least 17% better than ZIP,[8] and 7-Zip's own site reports that while compression ratio results are very dependent upon the data used for the tests, "usually, 7-Zip compresses to 7z format 30–70% better than to zip format, and 7-Zip compresses to zip format 2–10% better than most other zip-compatible programs".[9]

The 7z file format specification is distributed with the program's source code, in the "doc" subdirectory.

Others

7-Zip supports a number of other compression and non-compression archive formats (both for packing and unpacking), including 7z, ZIP, Gzip, bzip2, xz, tar and WIM. The utility also supports unpacking APM, ARJ, CHM, cpio, DEB, FLV, JAR, LHA/LZH, LZMA, MSLZ, Office Open XML, onepkg, RAR, RPM, smzip, SWF, XAR and Z archives and CramFS, DMG, FAT, HFS, ISO, MBR, NTFS, SquashFS, UDF and VHD disk images. 7-Zip supports the ZIPX format for unpacking only. It has had this support since at least version 9.20, which was released in late 2010.

7-Zip can open some MSI files, allowing access to the meta-files within along with the main contents. Some Microsoft CAB (LZX compression) and NSIS (LZMA) installer formats can be opened. Similarly, some Microsoft executable programs (.EXEs) that are self-extracting archives or otherwise contain archived content (e.g., some setup files) may be opened as archives.

When compressing ZIP or gzip files, 7-Zip uses its own DEFLATE encoder, which may achieve higher compression, but at lower speed, than the more common zlib DEFLATE implementation. The 7-Zip deflate encoder implementation is available separately as part of the AdvanceCOMP suite of tools.

The decompression engine for RAR archives was developed using source code of the unRAR program (which has a licensing restriction against creation of a RAR compressor). 7-Zip v15.12 support the RAR5 file format.[10] It can also unpack a few types of backup created by android stock recovery image.[11]

File manager

7-Zip comes with a file manager along with the standard archiver tools. The file manager has a toolbar with options to create an archive, extract an archive, test an archive to detect errors, copy, move, and delete files, and open a file properties menu exclusive to 7-zip. The file manager, by default, displays hidden files because it does not follow Windows Explorer's policies. The tabs show name, modification time, original and compressed sizes, attributes, and comments (all comments for a directory's files are stored in a text file on that directory called descript.ion, which can be edited offline).

When going up one directory on the root, all drives, removable or internal appear. Going up again shows a list with four options:

  • Computer: loads the drives list
  • Documents: loads user's documents, usually at %UserProfile%\My Documents
  • Network: loads a list of all network clients connected
  • \\.: Same as "Computer" except loads the drives in low-level NTFS access. This results in critical drive files and deleted files still existing on the drive to appear. (NOTE: Access to the active partition in low-level mode is not allowed for currently unknown reasons.)

Variants

Two command-line versions are provided: 7z.exe, using external libraries; and a standalone executable 7za.exe, containing built-in modules, but with compression/decompression support limited to 7z, ZIP, gzip, bzip2, Z and tar formats. A 64-bit version is available, with support for large memory maps, leading to faster compression. All versions support multi-threading.

The 7za.exe version of 7-Zip is available for Unix-like operating systems (including Linux, FreeBSD and Mac OS X), FreeDOS, OpenVMS and AmigaOS 4 under the name p7zip, also developed and maintained by Pavlov (7-zip).[3]

Features

7-Zip supports:

  • The 256-bit AES cipher. Encryption can be enabled for both files and the 7z directory structure. When the directory structure is encrypted, users are required to supply a password to see the filenames contained within the archive. WinZip-developed zip file AES encryption standard is also available in 7-Zip to encrypt ZIP archives with AES 256-bit, but it does not offer filename encryption as in 7z archives.[12]
  • Volumes of dynamically variable sizes, allowing use for backups on removable media such as writable CDs and DVDs.
  • Usability as a basic orthodox file manager when used in 2-panel mode.
  • Multiple-core CPU threading settings can be configured.
  • The ability to attempt to open EXE files as archives, allowing the decompression of data from inside many "Setup" or "Installer" or "Extract" type programs without having to launch them.
  • The ability to unpack archives with corrupted filenames, renaming the files as required.
  • The ability to create self-extracting single- (but not multi-) volume archives.
  • Command-line interface.[13]
  • Graphical user interface. The Windows version comes with its own GUI, however p7zip uses the GUI of the Unix/Linux Archive Manager.[14]

Reception

Snapfiles.com rates 7-zip 4.5 stars out of 5, noting that its "interface and additional features are fairly basic, but the compression ratio is outstanding".[15]

On TechRepublic, Justin James found the detailed settings for Windows File Manager integration were "appreciated" and called the compression/decompression benchmark utility "neat". And though the archive dialog has settings that "will confound most users", he concluded that "7-Zip fits a nice niche in between the built-in Windows capabilities and the features of the paid products, and it is able to handle a large variety of file formats in the process".[16]

The software has received awards. In 2007, SourceForge.net granted it community choice awards for "Technical Design" and for "Best Project".[17] In 2013, 7-Zip received Tom's Hardware Elite award due to superiority in speed and compression ratio.[18]

See also

References

  1. ↑ 1.0 1.1 1.2 Lua error in package.lua at line 80: module 'strict' not found.
  2. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  3. ↑ 3.0 3.1 Lua error in package.lua at line 80: module 'strict' not found.
  4. ↑ Pavlov, Igor. 7-zip. Retrieved 2012-10-31.
  5. ↑ Pavlov, Igor. License. 7-zip.org. Retrieved 2012-10-31.
  6. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  7. ↑ 7z format. 7-zip.org.
  8. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  9. ↑ 7-zip.org – Main Page
  10. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  11. ↑ Opened nandroid backup as well
  12. ↑ "AES Encryption Information: Encryption Specification AE-1 and AE-2". winzip.com. 30 January 2009, WinZip International LLC.
  13. ↑ "Command Line Syntax". sevenzip.osdn.jp.
  14. ↑ "Command Line Syntax"
  15. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  16. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  17. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  18. ↑ Lua error in package.lua at line 80: module 'strict' not found.

External links

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