$ gunzip mydatagz $ ls mydata in Software

Drawer ANSI/AIM Code 39 in Software $ gunzip mydatagz $ ls mydata

TIP On your desktop, you can extract the contents of an archive by locating it with the file manager

and double-clicking it You can also right-click and choose Open with Archive Manager This will start the File Roller application, which will open the archive, listing its contents You can then choose to extract the archive File Roller will use the appropriate tools to decompress the archive (bzip2, zip, or gzip) if compressed, and then extract the archive (tar) You can also compress archived tar files This results in files with the extensions targz Compressed archived files are often used for transmitting extremely large files across networks

Execution Sends compressed version of file to standard output; each file listed is separately compressed: gzip -c mydata preface > myfilesgz Decompresses a compressed file; or you can use gunzip: gzip -d myfilesgz gunzip myfilesgz Displays help listing Displays compressed and uncompressed size of each file listed: gzip -l myfilesgz Recursively searches for specified directories and compresses all the files in them; the search begins from the current working directory When used with gunzip, compressed files of a specified directory are uncompressed For each compressed or decompressed file, displays its name and the percentage of its reduction in size Determines the speed and size of the compression; the range is from 1 to 9 A lower number gives greater speed but less compression, resulting in a larger file that compresses and decompresses quickly Thus 1 gives the quickest compression but with the largest size; 9 results in a very small file that takes longer to compress and decompress The default is 6

Part II:

You can compress tar file members individually using the tar z option that invokes gzip With the z option, tar invokes gzip to compress a file before placing it in an archive Archives with members compressed with the z option, however, cannot be updated, nor is it possible to add to them All members must be compressed, and all must be added at the same time

You can also use the compress and uncompress commands to create compressed files They generate a file that has a Z extension and use a different compression format from gzip The compress and uncompress commands are not that widely used, but you may run across Z files occasionally You can use the uncompress command to decompress a Z file The gzip utility is the standard GNU compression utility and should be used instead of compress

Another popular compression utility is bzip2 It compresses files using the BurrowsWheeler block-sorting text compression algorithm and Huffman coding The command line options are similar to gzip by design, but they are not exactly the same (See the bzip2 Man page for a complete listing) You compress files using the bzip2 command and decompress with bunzip2 The bzip2 command creates files with the extension bz2 You can use bzcat to output compressed data to the standard output The bzip2 command compresses files in blocks and enables you to specify their size (larger blocks give you greater compression) As when using gzip, you can use bzip2 to compress tar archive files The following example compresses the mydata file into a bzip compressed file with the extension bz2:

To decompress, use the bunzip2 command on a bzip file:

Zip is a compression and archive utility modeled on PKZIP, which was used originally on DOS systems Zip is a cross-platform utility used on Windows, Mac, MS-DOS, OS/2, Unix, and Linux systems Zip commands can work with archives created by PKZIP and can use Zip archives You compress a file using the zip command This creates a Zip file with the zip extension If no files are listed, zip outputs the compressed data to the standard output You can also use the - argument to have zip read from the standard input To compress a directory, you include the -r option The first example archives and compresses a file: