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268 lines
10 KiB
XML
268 lines
10 KiB
XML
<?xml version="1.0"?>
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<!DOCTYPE modulesynopsis SYSTEM "../style/modulesynopsis.dtd">
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<?xml-stylesheet type="text/xsl" href="../style/manual.en.xsl"?>
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<!--
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Copyright 2002-2004 The Apache Software Foundation
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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<modulesynopsis metafile="mod_mime_magic.xml.meta">
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<name>mod_mime_magic</name>
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<description>Determines the MIME type of a file
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by looking at a few bytes of its contents</description>
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<status>Extension</status>
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<sourcefile>mod_mime_magic.c</sourcefile>
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<identifier>mime_magic_module</identifier>
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<summary>
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<p>This module determines the MIME type of files in the same
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way the Unix <code>file(1)</code> command works: it looks at the first
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few bytes of the file. It is intended as a "second line of defense"
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for cases that <module>mod_mime</module> can't resolve.</p>
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<p>This module is derived from a free version of the
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<code>file(1)</code> command for Unix, which uses "magic
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numbers" and other hints from a file's contents to figure out
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what the contents are. This module is active only if the magic
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file is specified by the <directive module="mod_mime_magic"
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>MimeMagicFile</directive> directive.</p>
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</summary>
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<section id="format"><title>Format of the Magic File</title>
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<p>The contents of the file are plain ASCII text in 4-5
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columns. Blank lines are allowed but ignored. Commented lines
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use a hash mark (<code>#</code>). The remaining lines are parsed for
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the following columns:</p>
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<table style="zebra" border="1">
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<tr><th>Column</th><th>Description</th></tr>
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<tr><td>1</td>
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<td>byte number to begin checking from<br />
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"<code>></code>" indicates a dependency upon the previous
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non-"<code>></code>" line</td></tr>
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<tr><td>2</td>
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<td>type of data to match
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<table border="1">
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<tr><td><code>byte</code></td>
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<td>single character</td></tr>
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<tr><td><code>short</code></td>
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<td>machine-order 16-bit integer</td></tr>
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<tr><td><code>long</code></td>
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<td>machine-order 32-bit integer</td></tr>
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<tr><td><code>string</code></td>
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<td>arbitrary-length string</td></tr>
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<tr><td><code>date</code></td>
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<td>long integer date (seconds since Unix epoch/1970)</td></tr>
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<tr><td><code>beshort</code></td>
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<td>big-endian 16-bit integer</td></tr>
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<tr><td><code>belong</code></td>
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<td>big-endian 32-bit integer</td></tr>
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<tr><td><code>bedate</code></td>
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<td>big-endian 32-bit integer date</td></tr>
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<tr><td><code>leshort</code></td>
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<td>little-endian 16-bit integer</td></tr>
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<tr><td><code>lelong</code></td>
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<td>little-endian 32-bit integer</td></tr>
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<tr><td><code>ledate</code></td>
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<td>little-endian 32-bit integer date</td></tr>
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</table></td></tr>
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<tr><td>3</td>
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<td>contents of data to match</td></tr>
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<tr><td>4</td>
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<td>MIME type if matched</td></tr>
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<tr><td>5</td>
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<td>MIME encoding if matched (optional)</td></tr>
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</table>
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<p>For example, the following magic file lines would recognize
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some audio formats:</p>
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<example>
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<pre># Sun/NeXT audio data
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0 string .snd
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>12 belong 1 audio/basic
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>12 belong 2 audio/basic
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>12 belong 3 audio/basic
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>12 belong 4 audio/basic
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>12 belong 5 audio/basic
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>12 belong 6 audio/basic
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>12 belong 7 audio/basic
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>12 belong 23 audio/x-adpcm</pre>
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</example>
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<p>Or these would recognize the difference between <code>*.doc</code>
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files containing Microsoft Word or FrameMaker documents. (These are
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incompatible file formats which use the same file suffix.)</p>
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<example>
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<pre># Frame
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0 string \<MakerFile application/x-frame
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0 string \<MIFFile application/x-frame
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0 string \<MakerDictionary application/x-frame
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0 string \<MakerScreenFon application/x-frame
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0 string \<MML application/x-frame
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0 string \<Book application/x-frame
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0 string \<Maker application/x-frame
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# MS-Word
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0 string \376\067\0\043 application/msword
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0 string \320\317\021\340\241\261 application/msword
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0 string \333\245-\0\0\0 application/msword</pre>
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</example>
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<p>An optional MIME encoding can be included as a fifth column.
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For example, this can recognize gzipped files and set the
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encoding for them.</p>
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<example>
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<pre># gzip (GNU zip, not to be confused with
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# [Info-ZIP/PKWARE] zip archiver)
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0 string \037\213 application/octet-stream x-gzip</pre>
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</example>
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</section>
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<section id="performance"><title>Performance Issues</title>
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<p>This module is not for every system. If your system is barely
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keeping up with its load or if you're performing a web server
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benchmark, you may not want to enable this because the
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processing is not free.</p>
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<p>However, an effort was made to improve the performance of
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the original <code>file(1)</code> code to make it fit in a busy web
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server. It was designed for a server where there are thousands of users
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who publish their own documents. This is probably very common
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on intranets. Many times, it's helpful if the server can make
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more intelligent decisions about a file's contents than the
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file name allows ...even if just to reduce the "why doesn't my
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page work" calls when users improperly name their own files.
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You have to decide if the extra work suits your
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environment.</p>
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</section>
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<section id="notes"><title>Notes</title>
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<p>The following notes apply to the <module>mod_mime_magic</module>
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module and are included here for compliance with contributors'
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copyright restrictions that require their acknowledgment.</p>
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<note>
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<p>mod_mime_magic: MIME type lookup via file magic numbers<br />
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Copyright (c) 1996-1997 Cisco Systems, Inc.</p>
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<p>This software was submitted by Cisco Systems to the Apache Group
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in July 1997. Future revisions and derivatives of this source code
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must acknowledge Cisco Systems as the original contributor of this
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module. All other licensing and usage conditions are those of the
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Apache Group.</p>
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<p>Some of this code is derived from the free version of the file
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command originally posted to comp.sources.unix. Copyright info for
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that program is included below as required.</p>
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</note>
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<note>
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<p> - Copyright (c) Ian F. Darwin, 1987. Written by Ian F. Darwin.</p>
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<p>This software is not subject to any license of the American
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Telephone and Telegraph Company or of the Regents of the University
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of California.</p>
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<p>Permission is granted to anyone to use this software for any
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purpose on any computer system, and to alter it and redistribute it
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freely, subject to the following restrictions:</p>
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<ol>
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<li>The author is not responsible for the consequences of use of
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this software, no matter how awful, even if they arise from flaws
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in it.</li>
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<li>The origin of this software must not be misrepresented, either
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by explicit claim or by omission. Since few users ever read
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sources, credits must appear in the documentation.</li>
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<li>Altered versions must be plainly marked as such, and must not
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be misrepresented as being the original software. Since few users
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ever read sources, credits must appear in the documentation.</li>
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<li>This notice may not be removed or altered.</li>
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</ol>
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</note>
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<note>
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<p>For compliance with Mr Darwin's terms: this has been very
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significantly modified from the free "file" command.</p>
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<ul>
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<li>all-in-one file for compilation convenience when moving from
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one version of Apache to the next.</li>
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<li>Memory allocation is done through the Apache API's pool
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structure.</li>
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<li>All functions have had necessary Apache API request or server
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structures passed to them where necessary to call other Apache API
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routines. (<em>i.e.</em>, usually for logging, files, or memory
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allocation in itself or a called function.)</li>
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<li>struct magic has been converted from an array to a single-ended
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linked list because it only grows one record at a time, it's only
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accessed sequentially, and the Apache API has no equivalent of
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<code>realloc()</code>.</li>
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<li>Functions have been changed to get their parameters from the
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server configuration instead of globals. (It should be reentrant
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now but has not been tested in a threaded environment.)</li>
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<li>Places where it used to print results to stdout now saves them
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in a list where they're used to set the MIME type in the Apache
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request record.</li>
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<li>Command-line flags have been removed since they will never be
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used here.</li>
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</ul>
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</note>
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</section>
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<directivesynopsis>
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<name>MimeMagicFile</name>
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<description>Enable MIME-type determination based on file contents
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using the specified magic file</description>
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<syntax>MimeMagicFile <var>file-path</var></syntax>
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<contextlist><context>server config</context><context>virtual host</context>
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</contextlist>
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<usage>
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<p>The <directive>MimeMagicFile</directive> directive can be used to
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enable this module, the default file is distributed at
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<code>conf/magic</code>. Non-rooted paths are relative to the
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<directive module="core">ServerRoot</directive>. Virtual hosts will use
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the same file as the main server unless a more specific setting is
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used, in which case the more specific setting overrides the main
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server's file.</p>
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<example><title>Example</title>
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MimeMagicFile conf/magic
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</example>
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</usage>
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</directivesynopsis>
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</modulesynopsis>
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