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<title>cksum - Cyclic Redundancy Checks</title>
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<div class="doctools">
<h1 class="doctools_title">cksum(n) 1.1.4 tcllib "Cyclic Redundancy Checks"</h1>
<div id="name" class="doctools_section"><h2><a name="name">Name</a></h2>
<p>cksum - Calculate a cksum(1) compatible checksum</p>
</div>
<div id="toc" class="doctools_section"><h2><a name="toc">Table Of Contents</a></h2>
<ul class="doctools_toc">
<li class="doctools_section"><a href="#toc">Table Of Contents</a></li>
<li class="doctools_section"><a href="#synopsis">Synopsis</a></li>
<li class="doctools_section"><a href="#section1">Description</a></li>
<li class="doctools_section"><a href="#section2">COMMANDS</a></li>
<li class="doctools_section"><a href="#section3">OPTIONS</a></li>
<li class="doctools_section"><a href="#section4">PROGRAMMING INTERFACE</a></li>
<li class="doctools_section"><a href="#section5">EXAMPLES</a></li>
<li class="doctools_section"><a href="#section6">AUTHORS</a></li>
<li class="doctools_section"><a href="#section7">Bugs, Ideas, Feedback</a></li>
<li class="doctools_section"><a href="#see-also">See Also</a></li>
<li class="doctools_section"><a href="#keywords">Keywords</a></li>
<li class="doctools_section"><a href="#category">Category</a></li>
<li class="doctools_section"><a href="#copyright">Copyright</a></li>
</ul>
</div>
<div id="synopsis" class="doctools_section"><h2><a name="synopsis">Synopsis</a></h2>
<div class="doctools_synopsis">
<ul class="doctools_requirements">
<li>package require <b class="pkgname">Tcl 8.2</b></li>
<li>package require <b class="pkgname">cksum <span class="opt">?1.1.4?</span></b></li>
</ul>
<ul class="doctools_syntax">
<li><a href="#1"><b class="cmd">::crc::cksum</b> <span class="opt">?<i class="arg">-format format</i>?</span> <span class="opt">?<i class="arg">-chunksize size</i>?</span> [ <i class="arg">-channel chan</i> | <i class="arg">-filename file</i> | <i class="arg">string</i> ]</a></li>
<li><a href="#2"><b class="cmd">::crc::CksumInit</b></a></li>
<li><a href="#3"><b class="cmd">::crc::CksumUpdate</b> <i class="arg">token</i> <i class="arg">data</i></a></li>
<li><a href="#4"><b class="cmd">::crc::CksumFinal</b> <i class="arg">token</i></a></li>
</ul>
</div>
</div>
<div id="section1" class="doctools_section"><h2><a name="section1">Description</a></h2>
<p>This package provides a Tcl implementation of the cksum(1) algorithm
based upon information provided at in the GNU implementation of this
program as part of the GNU Textutils 2.0 package.</p>
</div>
<div id="section2" class="doctools_section"><h2><a name="section2">COMMANDS</a></h2>
<dl class="doctools_definitions">
<dt><a name="1"><b class="cmd">::crc::cksum</b> <span class="opt">?<i class="arg">-format format</i>?</span> <span class="opt">?<i class="arg">-chunksize size</i>?</span> [ <i class="arg">-channel chan</i> | <i class="arg">-filename file</i> | <i class="arg">string</i> ]</a></dt>
<dd><p>The command takes string data or a channel or file name and returns a
checksum value calculated using the <b class="syscmd">cksum(1)</b> algorithm. The
result is formatted using the <i class="arg">format</i>(n) specifier provided or as
an unsigned integer (%u) by default.</p></dd>
</dl>
</div>
<div id="section3" class="doctools_section"><h2><a name="section3">OPTIONS</a></h2>
<dl class="doctools_definitions">
<dt>-channel <i class="arg">name</i></dt>
<dd><p>Return a checksum for the data read from a channel. The command will
read data from the channel until the <b class="cmd">eof</b> is true. If you need
to be able to process events during this calculation see the
<span class="sectref"><a href="#section4">PROGRAMMING INTERFACE</a></span> section</p></dd>
<dt>-filename <i class="arg">name</i></dt>
<dd><p>This is a convenience option that opens the specified file, sets the
encoding to binary and then acts as if the <i class="arg">-channel</i> option had
been used. The file is closed on completion.</p></dd>
<dt>-format <i class="arg">string</i></dt>
<dd><p>Return the checksum using an alternative format template.</p></dd>
</dl>
</div>
<div id="section4" class="doctools_section"><h2><a name="section4">PROGRAMMING INTERFACE</a></h2>
<p>The cksum package implements the checksum using a context variable to
which additional data can be added at any time. This is expecially
useful in an event based environment such as a Tk application or a web
server package. Data to be checksummed may be handled incrementally
during a <b class="cmd">fileevent</b> handler in discrete chunks. This can improve
the interactive nature of a GUI application and can help to avoid
excessive memory consumption.</p>
<dl class="doctools_definitions">
<dt><a name="2"><b class="cmd">::crc::CksumInit</b></a></dt>
<dd><p>Begins a new cksum context. Returns a token ID that must be used for the
remaining functions. An optional seed may be specified if required.</p></dd>
<dt><a name="3"><b class="cmd">::crc::CksumUpdate</b> <i class="arg">token</i> <i class="arg">data</i></a></dt>
<dd><p>Add data to the checksum identified by token. Calling
<em>CksumUpdate $token "abcd"</em> is equivalent to calling
<em>CksumUpdate $token "ab"</em> followed by
<em>CksumUpdate $token "cb"</em>. See <span class="sectref"><a href="#section5">EXAMPLES</a></span>.</p></dd>
<dt><a name="4"><b class="cmd">::crc::CksumFinal</b> <i class="arg">token</i></a></dt>
<dd><p>Returns the checksum value and releases any resources held by this
token. Once this command completes the token will be invalid. The
result is a 32 bit integer value.</p></dd>
</dl>
</div>
<div id="section5" class="doctools_section"><h2><a name="section5">EXAMPLES</a></h2>
<pre class="doctools_example">
% crc::cksum "Hello, World!"
2609532967
</pre>
<pre class="doctools_example">
% crc::cksum -format 0x%X "Hello, World!"
0x9B8A5027
</pre>
<pre class="doctools_example">
% crc::cksum -file cksum.tcl
1828321145
</pre>
<pre class="doctools_example">
% set tok [crc::CksumInit]
% crc::CksumUpdate $tok "Hello, "
% crc::CksumUpdate $tok "World!"
% crc::CksumFinal $tok
2609532967
</pre>
</div>
<div id="section6" class="doctools_section"><h2><a name="section6">AUTHORS</a></h2>
<p>Pat Thoyts</p>
</div>
<div id="section7" class="doctools_section"><h2><a name="section7">Bugs, Ideas, Feedback</a></h2>
<p>This document, and the package it describes, will undoubtedly contain
bugs and other problems.
Please report such in the category <em>crc</em> of the
<a href="http://core.tcl.tk/tcllib/reportlist">Tcllib Trackers</a>.
Please also report any ideas for enhancements you may have for either
package and/or documentation.</p>
<p>When proposing code changes, please provide <em>unified diffs</em>,
i.e the output of <b class="const">diff -u</b>.</p>
<p>Note further that <em>attachments</em> are strongly preferred over
inlined patches. Attachments can be made by going to the <b class="const">Edit</b>
form of the ticket immediately after its creation, and then using the
left-most button in the secondary navigation bar.</p>
</div>
<div id="see-also" class="doctools_section"><h2><a name="see-also">See Also</a></h2>
<p><a href="crc32.html">crc32(n)</a>, <a href="sum.html">sum(n)</a></p>
</div>
<div id="keywords" class="doctools_section"><h2><a name="keywords">Keywords</a></h2>
<p><a href="../../../../index.html#checksum">checksum</a>, <a href="../../../../index.html#cksum">cksum</a>, <a href="../../../../index.html#crc">crc</a>, <a href="../../../../index.html#crc32">crc32</a>, <a href="../../../../index.html#cyclic_redundancy_check">cyclic redundancy check</a>, <a href="../../../../index.html#data_integrity">data integrity</a>, <a href="../../../../index.html#security">security</a></p>
</div>
<div id="category" class="doctools_section"><h2><a name="category">Category</a></h2>
<p>Hashes, checksums, and encryption</p>
</div>
<div id="copyright" class="doctools_section"><h2><a name="copyright">Copyright</a></h2>
<p>Copyright © 2002, Pat Thoyts</p>
</div>
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