File archiver: Difference between revisions
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{{Short description|Utility software for combining files}} | {{Short description |Utility software for combining files}} | ||
{{refimprove|date=August 2016}} | {{refimprove|date=August 2016}} | ||
A '''file archiver''' is [[utility software]] that combines [[computer file |files]] into a single [[archive file]] {{endash}} or in less common cases, multiple files. A relatively simple implementation might include the content of each file plus its [[file name |name]]. A more advanced implementation stores additional [[metadata]], such as the [[Timestamping (computing)|timestamps]], [[file attribute]]s and access control information. An archiver might [[lossless data compression |compress]] input file content to reduce the size of the resulting archive. | |||
In addition to creating an archive, the same utility may also support extracting the contained file content to recreate the original files. | |||
==Multics== | ==Multics== | ||
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As the [[Unix]] archive tools [[ar (Unix)|ar]], [[tar (file format)|tar]], and [[cpio]] do not provide compression, other tools, such as [[gzip]], [[bzip2]], or [[XZ Utils|xz]], are used to compress an archive file after it is created and to decompress before extracting. | As the [[Unix]] archive tools [[ar (Unix)|ar]], [[tar (file format)|tar]], and [[cpio]] do not provide compression, other tools, such as [[gzip]], [[bzip2]], or [[XZ Utils|xz]], are used to compress an archive file after it is created and to decompress before extracting. | ||
Not only does separating archiving from compressing follow the [[Unix philosophy]] | Not only does separating archiving from compressing follow the [[Unix philosophy]]—that each tool should provide a single capability, not attempt to accomplish everything with one tool—it has the following advantages: | ||
* As compression technology progresses, users may use a different compression tool without having to change how they use the archiver. | * As compression technology progresses, users may use a different compression tool without having to change how they use the archiver. | ||
* [[Solid compression]] allows the compressor to take advantage of redundancy across the multiple archived files in order to achieve better compression than simply compressing each file individually. | * [[Solid compression]] allows the compressor to take advantage of redundancy across the multiple archived files in order to achieve better compression than simply compressing each file individually. | ||