96 lines
2.8 KiB
HTML
96 lines
2.8 KiB
HTML
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
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<html>
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<head>
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<meta name="generator" content="HTML Tidy, see www.w3.org">
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<meta http-equiv="Content-Type" content=
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"text/html; charset=utf-8">
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<title>uncompress - Expand compressed data</title>
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<LINK rel="stylesheet" type="text/css" href="../rzahg/ic.css">
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</HEAD>
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<body bgcolor="#FFFFFF">
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<!-- Java sync-link -->
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<SCRIPT LANGUAGE="Javascript" SRC="../rzahg/synch.js" TYPE="text/javascript"></SCRIPT>
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<h2>uncompress - Expand
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compressed data</h2>
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<p><strong>Synopsis</strong></p>
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<p><strong>uncompress [-cv] [-b</strong> <em>bits</em>]
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[<em>file</em> ...]</p>
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<p><strong>Description</strong></p>
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<p>The <strong>uncompress</strong> utility restores the compressed
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<em>files</em> to their original form, renaming the files by
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deleting the ".Z" extension.</p>
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<p>If renaming <em>file</em> would cause files to be overwritten
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and the standard input device is a terminal, the user is prompted
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(on standard error) for confirmation. If prompting is not possible
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or confirmation is not received, the files are not overwritten.</p>
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<p><strong>Options</strong></p>
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<dl>
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<dt><strong>-b</strong> <em>bits</em></dt>
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<dd>Specify the bits code limit (see below for details).</dd>
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<dt><strong>-c</strong></dt>
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<dd>Uncompressed output is written to the standard output. No files
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are modified.</dd>
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<dt><strong>-v</strong></dt>
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<dd>Print the percentage of expansion for each file.</dd>
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</dl>
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<p><strong>Operands</strong></p>
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<p>Each <em>file</em> is a pathname of a file to uncompress. If no
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<em>files</em> are specified, the standard input is uncompressed to
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the standard output. If either the input and output files are not
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regular files, the checks for reduction in size and file
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overwriting are not performed, the input file is not removed, and
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the attributes of the input file are not retained.</p>
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<p><strong>Extended Description</strong></p>
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<p>The <strong>uncompress</strong> utility uses a modified
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Lempel-Ziv algorithm. Common substrings in the file are first
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replaced by 9-bit codes 257 and up. When code 512 is reached, the
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algorithm switches to 10-bit codes and continues to use more bits
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until the limit specified by the <strong>-b</strong> flag is
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reached (the default is 16). Bits must be between 9 and 16.</p>
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<p>The amount of compression obtained depends on the size of the
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input, the number of bits per code, and the distribution of common
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substrings. Typically, text such as source code or English is
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reduced by 50-60%.</p>
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<p><strong>Exit Status</strong></p>
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<ul>
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<li>0 on success</li>
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<li>>0 if an error occurs.</li>
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</ul>
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<p><strong>Related information</strong></p>
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<ul>
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<li><a href="compress.htm">compress - Compress data</a></li>
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<li><a href="zcat.htm">zcat - Expand and concatenate data</a></li>
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</ul>
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<!-- end ibmbody========================================================= -->
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</body>
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</html>
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