📄 pack.html

📁 unix 下的C开发手册,还用详细的例程。
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><html><head><!-- Copyright 1997 The Open Group, All Rights Reserved --><title>pack</title></head><body bgcolor=white><center><font size=2>The Single UNIX &reg; Specification, Version 2<br>Copyright &copy; 1997 The Open Group</font></center><hr size=2 noshade><h4><a name = "tag_001_014_1612">&nbsp;</a>NAME</h4><blockquote>pack - compress files (<b><a href="intro.html#tag_001_003_003">LEGACY</a></b>)</blockquote><h4><a name = "tag_001_014_1613">&nbsp;</a>SYNOPSIS</h4><blockquote><pre><code>pack <b>[</b>-f<b>][</b>-<b>] </b><i>file</i>...</code></pre></blockquote><h4><a name = "tag_001_014_1614">&nbsp;</a>DESCRIPTION</h4><blockquote>The<i>pack</i>utility attempts to store the specified files in a compressed form.Each input file is replaced by a packed file<i>file</i><b>.z</b>.If the invoking process has appropriate privileges, the ownership, modes,access time, and modification time of the original file are preserved.  If<i>pack</i>is successful,<i>file</i>will be removed.Packed files can be restored to their original form using<i><a href="unpack.html">unpack</a></i>or<i><a href="pcat.html">pcat</a></i>.<p>No packing will occur if:<ul><p><li>The file appears to be already packed.<p><li>The filename has more than{NAME_MAX}-2bytes.<p><li>The file has links.<p><li>The file is a directory.<p><li>The file cannot be opened.<p><li>The file is empty.<p><li>No disk storage will be saved by packing.<p><li>A file called<i>file</i><b>.z</b>already exists.<p><li>The<b>.z</b>file cannot be created.<p><li>An I/O error occurred during processing.<p></ul><p>The last segment of the filename must contain no more than{NAME_MAX}-2bytes to allow space for the appended<b>.z</b>extension.</blockquote><h4><a name = "tag_001_014_1615">&nbsp;</a>OPTIONS</h4><blockquote>The<i>pack</i>utility supports the <b>XBD</b> specification, <a href="../xbd/utilconv.html#usg"><b>Utility Syntax Guidelines</b>&nbsp;</a> .The following option is supported:<p><dl compact><dt><b>-f</b><dd>Force packing of files.This is useful for causing an entire directory to be packedeven if some of the files will not benefit.</dl></blockquote><h4><a name = "tag_001_014_1616">&nbsp;</a>OPERANDS</h4><blockquote>The following operands are supported:<dl compact><dt><b>-</b><dd>Sets an internal flag that causes the number of times eachbyte is used, its relative frequency and the code for the byteto be written to standard output.Additional occurrences of - in place of<i>file</i>will cause the internal flag to be set and reset.<dt><i>file</i><dd>A pathname of a file to be packed;<i>file</i>can include or omit the<b>.z</b>suffix.</dl></blockquote><h4><a name = "tag_001_014_1617">&nbsp;</a>STDIN</h4><blockquote>Not used.</blockquote><h4><a name = "tag_001_014_1618">&nbsp;</a>INPUT FILES</h4><blockquote>The input files are regular files.<br></blockquote><h4><a name = "tag_001_014_1619">&nbsp;</a>ENVIRONMENT VARIABLES</h4><blockquote>The following environment variables may affect the execution of<i>pack</i>:<dl compact><dt><i>LANG</i><dd>Provide a default value for the internationalisation variablesthat are unset or null.If<i>LANG</i>is unset or null, the corresponding value from theimplementation-dependent default locale will be used.If any of the internationalisation variables contains an invalid setting, theutility will behave as if none of the variables had been defined.<dt><i>LC_ALL</i><dd>If set to a non-empty string value,override the values of all the other internationalisation variables.<dt><i>LC_CTYPE</i><dd>Determine thelocale for the interpretation of sequences of bytes of text data ascharacters (for example, single- as opposed to multi-byte charactersin arguments).<dt><i>LC_MESSAGES</i><dd>Determine the locale that should be used to affectthe format and contents of diagnosticmessages written to standard error,and informative messages written to standard output.<dt><i>NLSPATH</i><dd>Determine the location of message cataloguesfor the processing of<i>LC_MESSAGES .</i></dl></blockquote><h4><a name = "tag_001_014_1620">&nbsp;</a>ASYNCHRONOUS EVENTS</h4><blockquote>If an error or signal occurs, the<i>file</i><b>.z</b>file is not created and the original file is unchanged.</blockquote><h4><a name = "tag_001_014_1621">&nbsp;</a>STDOUT</h4><blockquote>The standard output is a text file containing one line foreach file packed, with the following formatused in the POSIX locale:<p><code><tt>"pack: %s: %2.1f%% Compression\n"</tt>, <i>file</i>,&lt;<i>percent&nbsp;compression</i>&gt;</code>or:<pre><code><tt>"pack: %s: no saving - file unchanged\n"</tt>, <i>file</i></code></pre><p>If the - operand is specified and the internal flag is set,additional messages of unspecified format will be written tostandard output as indicated in the OPERANDS section.</blockquote><h4><a name = "tag_001_014_1622">&nbsp;</a>STDERR</h4><blockquote>Used only for diagnostic messages.</blockquote><h4><a name = "tag_001_014_1623">&nbsp;</a>OUTPUT FILES</h4><blockquote>Packed files of unspecified format are created with names of the form<i>file</i><b>.z</b>.</blockquote><h4><a name = "tag_001_014_1624">&nbsp;</a>EXTENDED DESCRIPTION</h4><blockquote>None.</blockquote><h4><a name = "tag_001_014_1625">&nbsp;</a>EXIT STATUS</h4><blockquote>The following exit values are returned:<dl compact><dt>0<dd>Successful completion.<dt>&gt;0<dd>An error occurred.</dl></blockquote><h4><a name = "tag_001_014_1626">&nbsp;</a>CONSEQUENCES OF ERRORS</h4><blockquote>Default.</blockquote><h4><a name = "tag_001_014_1627">&nbsp;</a>APPLICATION USAGE</h4><blockquote>The amount of compression obtained depends on the size of theinput file and the character frequency distribution.Because a decodingtree may form the first part of each<b>.z</b>file, it is usually not worthwhileto pack small files, unless the character frequencydistribution is very skewed, which may occur with printer plots or pictures.<p>Typically, text files are reduced to 60-75% of their original size.Object files, which use a larger character set and have a moreuniform distribution of characters, show little compression, thepacked versions typically being about 90% of the original size.<p>Packed files are not necessarily portable to other systems.<p>Applications should migrate to the<i><a href="compress.html">compress</a></i>utility.The<i><a href="compress.html">compress</a></i>utility offers two advantages over<i>pack</i>:<ul><p><li>The algorithm used to create the output files isfrequently more effective in reducing the sizes of files.<p><li>The<i><a href="compress.html">compress</a></i>utility can compress data from its standard input,not just a named regular file.Thus, it is useful in pipelines.<p></ul></blockquote><h4><a name = "tag_001_014_1628">&nbsp;</a>EXAMPLES</h4><blockquote>None.</blockquote><h4><a name = "tag_001_014_1629">&nbsp;</a>FUTURE DIRECTIONS</h4><blockquote>None.</blockquote><h4><a name = "tag_001_014_1630">&nbsp;</a>SEE ALSO</h4><blockquote><i><a href="pcat.html">pcat</a></i>,<i><a href="unpack.html">unpack</a></i>,<i><a href="compress.html">compress</a></i>.</blockquote><hr size=2 noshade><center><font size=2>UNIX &reg; is a registered Trademark of The Open Group.<br>Copyright &copy; 1997 The Open Group<br> [ <a href="../index.html">Main Index</a> | <a href="../xshix.html">XSH</a> | <a href="../xcuix.html">XCU</a> | <a href="../xbdix.html">XBD</a> | <a href="../cursesix.html">XCURSES</a> | <a href="../xnsix.html">XNS</a> ]</font></center><hr size=2 noshade></body></html>
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