Cabinet (or CAB) is an archive-file format for Microsoft Windows that supports

lossless data compression Lossless compression is a class of data compression that allows the original data to be perfectly reconstructed from the compressed data with no loss of information. Lossless compression is possible because most real-world data exhibits statist ...

and embedded

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s used for maintaining archive integrity. Cabinet files have .cab

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s and are recognized by their first four bytes (also called their '' magic number'') ''MSCF''. Cabinet files were known originally as Diamond files.

Design

A CAB archive can contain up to 65535 ''folders'' (distinct to standard operating system directories), each of which can contain up to 65535 files for a maximum of 4294836225. Internally, each folder is treated as a single compressed block, which provides more efficient compression than individually compressing each file. Every entry in a folder has to be a file.Microsoft Cabinet Format
/ref> Due to this structure, it is not possible to store empty folders in CAB archives. The following shows an example a CAB file structure, demonstrating the relationship between folders and files: * CAB file ** First folder *** *** ** Second folder *** *** How paths should be handled is not specified in the CAB file format, leaving it to the software implementation: * Some affix file paths to filenames only, as if all files in a CAB archive are in a single folder. IExpress works this way, as does Microsoft Windows Explorer, which can open CAB archives as a folder. * Some can store the paths, and upon extraction, create folders as necessary. and (tools from Microsoft Cabinet SDK) as well as and (third-party open-source tools) work this way. * , only since version 6 (which is included from Windows Vista to above) can extract files to their paths. The previous versions don't do it. The CAB file format may employ the following compression algorithms: * DEFLATE: invented by Phil Katz, the author of the ZIP file format (specifically, the MSZIP encapsulation) * Quantum compression: licensed from David Stafford, the author of the Quantum archiver (not available in all versions of makecab.exe/diamond.exe) *

LZX LZX is an LZ77 family compression algorithm, a slightly improved version of DEFLATE. imlib: the open source Windows Imaging (WIM) library - Compression algorit hmhttps://wimlib.net/compression.html/ref> It is also the name of a file archiver wit ...

: invented by Jonathan Forbes and Tomi Poutanen, given to Microsoft when Forbes joined the company * NULL: stored A CAB archive can reserve empty spaces in the archive as well as for each file in the archive, for some application-specific uses like digital signatures or arbitrary data.

Implementations

Microsoft Windows supports creating CAB archive files using the makecab

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utility. It supports extracting the contents of a CAB archive files using

File Explorer File Explorer, previously known as Windows Explorer, is a file manager application that is included with releases of the Microsoft Windows operating system from Windows 95 onwards. It provides a graphical user interface for accessing the file ...

Setup API Windows Installer (msiexec.exe, previously known as Microsoft Installer, codename Darwin) is a software component and application programming interface (API) of Microsoft Windows used for the installation, maintenance, and removal of software ...

, and using the command-line

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expand.exe,expand - Windows CMD - SS64.com
/ref> extract.exe and extrac32.exe.
/ref> Other well-known software with CAB archive support includes WinZip, WinRAR or 7-Zip. The aforementioned cabextract is a common tool for Linux systems, but is only capable of extracting archives. The gcab tool however can both extract and create CAB archives. For a full list, see .

Uses

A variety of

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installation technologies use the CAB format: these include

Windows Installer Windows Installer (msiexec.exe, previously known as Microsoft Installer, codename Darwin) is a software component and application programming interface (API) of Microsoft Windows used for the installation, maintenance, and removal of softwar ...

Device Installer A device is usually a constructed tool. Device may also refer to: Technology Computing * Device, a colloquial term encompassing desktops, laptops, tablets, smartphones, etc. * Device file, an interface of a device driver * Peripheral, any devic ...

, Theme Pack and AdvPack (used by

Internet Explorer Internet Explorer (formerly Microsoft Internet Explorer and Windows Internet Explorer, commonly abbreviated IE or MSIE) is a series of graphical user interface, graphical web browsers developed by Microsoft which was used in the Microsoft Wind ...

to install

ActiveX ActiveX is a deprecated software framework created by Microsoft that adapts its earlier Component Object Model (COM) and Object Linking and Embedding (OLE) technologies for content downloaded from a network, particularly from the World Wide Web. ...

components). CAB files are also often associated with self-extracting programs like IExpress where the executable program extracts the associated CAB file. CAB files are also sometimes embedded into other files. For example, MSI and MSU files usually include one or more embedded CAB files. Windows uses the cabinet format to archive its Component-Based Servicing (CBS) log, which is kept in the folder . A bug in the compression process can cause run-away generation of useless log files both in that folder and in , which can consume disk storage until completely filling the hard drive. Deletion of the files without following a specific procedure can cause the deleted files to be regenerated at an increased pace. On

Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which i ...

systems, CAB archives are used by fwupd to distribute

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updates from hardware vendors that can be flashed on

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Related formats

The .cab filename extension is also used by other installer programs (e.g. InstallShield) for their own proprietary archiving formats. InstallShield uses zlib for compression (see Deflate), but their headers are not the same as for Microsoft CAB files so they are incompatible and cannot be manipulated or edited with the programs that are made for standard cabinet format. Specialized third-party utilities, such as Unshield, can extract this specific proprietary format. This format has a different magic number of . Windows CE installer uses a variant of Microsoft CAB format with a magic. The compression is typically NONE, but MSZIP can also be found. Microsoft Publisher has a "Pack and Go" feature that bundles a publisher document, together with all external links, into a CAB file with a .PUZ extension. These files are meant to be activated with a companion .EXE file which is distributed along with the .PUZ file. These files may be opened with any CAB file extraction program.

References

External links