Open RAR File

Information, tips and instructions

GZ and TAR Files

GZ file extension is used by files in GZIP format. GZIP file format was introduced in 1992 by Jean-loup Gailly. Similar to ZIP file format GZIP is using DEFLATE algorithm (combination of LZ77 and Huffman coding) for compression. GZIP was initially developed with a goal to replace “compress” utility for Unix. “Compress” utility used LZW algorithm which had a similar performance to DEFLATE but resulted in significantly larger compressed files. Given exponential increase in computer performance, DEFLATE algorithm and gzip proved to be the best choice moving forward. At this moment GZIP is a leading compression format for Unix and Linux operating systems. It is also used as one of the compression schemes in HTTP protocol.

GZIP has a significant difference from other archivers is that it can only work on a single file. You cannot give GZIP an entire folder and compress it. In order for GZIP to work with multiple files another utility called TAR is typically used. TAR utility can merge multiple files from multiple folders into one large TAR file and preserve file permissions, directory structure, names and time stamps. Also TAR can execute GZIP compression for every file it adds to the TAR archive. When TAR is used together with GZIP the resulting file extension for the archive will be .tar.gz or .tgz which means that TAR was used to merge GZIP compressed files into one file.

In order to create a .tar.gz archive the following terminal command should be used:

tar -zcvf tar-name.tar.gz source-folder

To extract a .tar.gz archive use the following command:

tar -zxvf tar-name.tar.gz

Here -c means create archive file and -x means extract archive files. -z means that all files should be compressed with GZIP. -v instructs TAR utility to show progress of compression and -f outputs resulting archive to a file.

GZIP utility is open source and GZIP format is available for use free of any legal obligations.

Recently bzip2 utility on Unix and Linux machines and 7-zip on Windows machines started to take some market share from gzip and zip correspondingly because of the better compression rate provided by Burrows-Wheeler and LZMA algorithms correspondingly. But better compression rate comes at significantly slower compression speeds and gzip still holds a significant share of the compression market.

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Extension Details
  Compression file format
Identifying Characters
  Hex: 52 61 72 21
  ASCII: Rar!
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