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<head>
<title>Zlibc</title>
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<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
<a name="Introduction"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[ < ]</td>
<td valign="middle" align="left">[<a href="#Location" title="Next section in reading order"> > </a>]</td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[ << ]</td>
<td valign="middle" align="left">[ Up ]</td>
<td valign="middle" align="left">[<a href="#Location" title="Next chapter"> >> </a>]</td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Introduction" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Variable-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<h1 class="unnumbered">Introduction</h1>
<p>The zlibc package allows transparent on the fly uncompression of gzipped
files. Your programs will be able to access any compressed file, just
as if they were uncompressed. Zlibc will transparently uncompresses the
data from these files as soon as they are read, just as a compressed
filesystem would do. No kernel patch, no recompilation of these
executables and no recompilation of the libraries is needed.
</p>
<p>It is not (yet) possible execute compressed files with zlibc. However,
there is another package, called <code>tcx</code>, which is able to uncompress
executables on the fly. On the other hand <code>tcx</code> isn’t able to
uncompress data files on the fly. Fortunately, the both zlibc and tcx
may coexist on the same machine without problems.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top"><a href="#Location">1. Where to get zlibc</a></td><td> </td><td align="left" valign="top"> Where to get zlibc and early bug fixes
</td></tr>
<tr><td align="left" valign="top"><a href="#Installing-zlibc">2. Installing zlibc</a></td><td> </td><td align="left" valign="top"> How to install zlibc
</td></tr>
<tr><td align="left" valign="top"><a href="#Using-zlibc">3. Using zlibc</a></td><td> </td><td align="left" valign="top"> How to configure your system to use zlibc
</td></tr>
<tr><td align="left" valign="top"><a href="#How-it-works">4. How it works</a></td><td> </td><td align="left" valign="top"> The general principles behind zlibc
</td></tr>
<tr><td align="left" valign="top"><a href="#Customization">5. Customization</a></td><td> </td><td align="left" valign="top"> How to customize zlibc to your needs
</td></tr>
<tr><td align="left" valign="top"><a href="#Porting-zlibc">6. Porting zlibc</a></td><td> </td><td align="left" valign="top"> How to port zlibc to new architectures
</td></tr>
<tr><td align="left" valign="top"><a href="#Variable-Index">Variable index</a></td><td> </td><td align="left" valign="top"> Variable Index
</td></tr>
<tr><td align="left" valign="top"><a href="#Concept-Index">Concept index</a></td><td> </td><td align="left" valign="top"> Concept Index
</td></tr>
</table>
<p>This documentation looks most pretty when printed or as html. Indeed,
in the info version certain examples are difficult to read due to the
confusing quoting conventions of info.
</p>
<a name="index-bugs"></a>
<a name="index-ALPHA-patches"></a>
<a name="index-patches"></a>
<a name="index-diffs"></a>
<a name="index-mailing-list"></a>
<hr size="6">
<a name="Location"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Introduction" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#Installing-zlibc" title="Next section in reading order"> > </a>]</td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Introduction" title="Beginning of this chapter or previous chapter"> << </a>]</td>
<td valign="middle" align="left">[<a href="#Introduction" title="Up section"> Up </a>]</td>
<td valign="middle" align="left">[<a href="#Installing-zlibc" title="Next chapter"> >> </a>]</td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Introduction" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Variable-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Where-to-get-zlibc"></a>
<h1 class="chapter">1. Where to get zlibc</h1>
<p>Zlibc can be found at the following places (and their mirrors):
</p><table><tr><td> </td><td><pre class="example">ftp://zlibc.linux.lu/zlibc-0.9k.tar.gz
ftp://www.tux.org/pub/knaff/zlibc/zlibc-0.9k.tar.gz
ftp://ibiblio.unc.edu/pub/Linux/libs/compression/zlibc-0.9k.tar.gz
ftp://ftp.gnu.org/gnu/zlibc/compression/zlibc-0.9k.tar.gz
</pre></td></tr></table>
<p>Before reporting a bug, make sure that it has not yet been fixed in the
Alpha patches which can be found at:
</p><table><tr><td> </td><td><pre class="example">http://zlibc.linux.lu/
http://www.tux.org/pub/knaff/zlibc
</pre></td></tr></table>
<p>These patches are named
<code>zlibc-</code><var>version</var><code>-</code><var>ddmm</var><code>.taz</code>, where version
stands for the base version, <var>dd</var> for the day and <var>mm</var> for the
month. Due to a lack of space, I usually leave only the most recent
patch.
</p>
<p>There is an zlibc mailing list at zlibc @ www.tux.org . Please
send all bug reports to this list. You may subscribe to the list by
sending a message with ’subscribe zlibc @ www.tux.org’ in its
body to majordomo @ www.tux.org . (N.B. Please remove the spaces
around the "@" both times. I left them there in order to fool
spambots.) Announcements of new zlibc versions will also be sent to
the list, in addition to the linux announce newsgroups. The mailing
list is archived at http://www.tux.org/hypermail/zlibc/latest
</p>
<hr size="6">
<a name="Installing-zlibc"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Location" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#Using-zlibc" title="Next section in reading order"> > </a>]</td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Location" title="Beginning of this chapter or previous chapter"> << </a>]</td>
<td valign="middle" align="left">[<a href="#Introduction" title="Up section"> Up </a>]</td>
<td valign="middle" align="left">[<a href="#Using-zlibc" title="Next chapter"> >> </a>]</td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Introduction" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Variable-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Installing-zlibc-1"></a>
<h1 class="chapter">2. Installing zlibc</h1>
<a name="index-LD_005fPRELOAD"></a>
<a name="index-Installation"></a>
<a name="index-Set_002duid-programs"></a>
<a name="index-Boot-problems"></a>
<ol>
<li>
If you install zlibc on Linux, make sure that your shared loader
(ld-linux.so.1/ld.so) understands <code>LD_PRELOAD</code>. (Best if
ld.so-1.8.5 or more recent)
</li><li>
Type <code>./configure</code>. This runs the GNU autoconfigure script which
configures the ‘<tt>Makefile</tt>’ and the ‘<tt>config.h</tt>’ file. You may
compile time configuration options to <code>./configure</code>, see for
details.
</li><li>
Type <code>make</code> to compile zlibc.
</li><li>
Type <code>make install</code> to install zlibc and associated programs to its
final target.
</li><li>
To use this module, set the environment variable <code>LD_PRELOAD</code> to
point to the object. Example (sh syntax):
<table><tr><td> </td><td><pre class="example"> LD_PRELOAD=/usr/local/lib/uncompress.so
export LD_PRELOAD
</pre></td></tr></table>
<p>or (csh syntax):
</p>
<table><tr><td> </td><td><pre class="example"> setenv LD_PRELOAD /usr/local/lib/uncompress.so
</pre></td></tr></table>
<p>On linux, use /lib/uncompress.so instead of /usr/local/lib/uncompress.so .
</p>
<p>You might want to put these lines in your ‘<tt>.profile</tt>’ or
‘<tt>.cshrc</tt>’ in order to have the uncompressing functions available all
the time.
</p></li><li>
Compress your files using gzip and enjoy
</li></ol>
<p>For security reasons, the dynamic loader disregards environmental
variables such as <code>LD_PRELOAD</code> when executing set uid programs.
</p>
<p>However, on Linux, you can use zlibc with set uid programs too, by using
one of the two methods described below:
</p>
<ol>
<li>
You may ing the path to ‘<tt>uncompress.so</tt>’ into
‘<tt>/etc/ld.so.preload</tt>’ instead of using <code>LD_PRELOAD</code>.
<p><strong>WARNING</strong>: If you use ‘<tt>/etc/ld.so.preload</tt>’, be sure to
install ‘<tt>uncompress.so</tt>’ on your root filesystem, for instance in
<code>/lib</code>, as is done by the default configuration. Using a directory
which is not available at boot time, such as /usr/local/lib will cause
trouble at the next reboot!
</p>
<p>It is also careful to remove zlibc from ‘<tt>/etc/ld.so.preload</tt>’ when
installing a new version. First test it out using <code>LD_PRELOAD</code>,
and only if everything is ok, put it back into
‘<tt>/etc/ld.so.preload</tt>’.
</p>
</li><li>
If you have a version of <code>ld.so</code> which is more recent than
<code>1.9.0</code>, you can set <code>LD_PRELOAD</code> to just contain the basename
of ‘<tt>uncompress.so</tt>’ without the directory. In that case, the file is
found as long as it is in the shared library path (which usually
contains ‘<tt>/lib</tt>’ and ‘<tt>/usr/lib</tt>’)). Because the search is
restricted to the library search path, this also works for set-uid
programs.
<p>Example (sh syntax):
</p>
<table><tr><td> </td><td><pre class="example"> LD_PRELOAD=uncompress.so
export LD_PRELOAD
</pre></td></tr></table>
<p>or (csh syntax):
</p>
<table><tr><td> </td><td><pre class="example"> setenv LD_PRELOAD uncompress.so
</pre></td></tr></table>
<p>The advantage of this approach over ‘<tt>ld.so.preload</tt>’ is that zlibc
can more easily be switched off in case something goes wrong.
</p>
</li></ol>
<hr size="6">
<a name="Using-zlibc"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Installing-zlibc" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#Zlibc-and-links" title="Next section in reading order"> > </a>]</td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Installing-zlibc" title="Beginning of this chapter or previous chapter"> << </a>]</td>
<td valign="middle" align="left">[<a href="#Introduction" title="Up section"> Up </a>]</td>
<td valign="middle" align="left">[<a href="#How-it-works" title="Next chapter"> >> </a>]</td>
<td valign="middle" align="left"> </td>
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<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Introduction" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Variable-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Using-zlibc-1"></a>
<h1 class="chapter">3. Using zlibc</h1>
<a name="index-Symbolic-links"></a>
<p>Once zlibc is installed, simply compress your biggest datafiles
using gzip. Your programs are now able to uncompress these files on the
fly whenever they need them.
</p>
<hr size="6">
<a name="Zlibc-and-links"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Using-zlibc" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#Symbolic-links" title="Next section in reading order"> > </a>]</td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Using-zlibc" title="Beginning of this chapter or previous chapter"> << </a>]</td>
<td valign="middle" align="left">[<a href="#Using-zlibc" title="Up section"> Up </a>]</td>
<td valign="middle" align="left">[<a href="#How-it-works" title="Next chapter"> >> </a>]</td>
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<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Introduction" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Variable-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<h2 class="section">3.1 Zlibc and links</h2>
<hr size="6">
<a name="Symbolic-links"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Zlibc-and-links" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#Hard-links" title="Next section in reading order"> > </a>]</td>
<td valign="middle" align="left"> </td>
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<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Introduction" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Variable-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<h3 class="subsection">3.1.1 Symbolic links</h3>
<p>After compressing your datafiles, you also need to change any potential
symbolic links pointing to them. Let’s suppose that ‘<tt>x</tt>’ is a
symlink to ‘<tt>tstfil</tt>’:
</p>
<table><tr><td> </td><td><pre class="example">> echo 'this is a test' >tstfil
> ln -s tstfil x
> ls -l
total 1
-rw-r--r-- 1 alknaff sirac 15 Feb 25 19:40 tstfil
lrwxrwxrwx 1 alknaff sirac 8 Feb 25 19:40 x -> tstfil
</pre></td></tr></table>
<p>After compressing it, you’ll see the following listing:
</p>
<table><tr><td> </td><td><pre class="example">> gzip tstfil
> ls -l
total 1
pr--r--r-- 1 alknaff sirac 15 Feb 25 19:40 tstfil
lrwxrwxrwx 1 alknaff sirac 8 Feb 25 19:40 x -> tstfil
</pre></td></tr></table>
<p>‘<tt>Tstfil</tt>’ is now shown as a pipe by zlibc in order to warn programs
that they cannot seek in it. Zlibc still shows it with its old name,
and you can directly look at its contents:
</p><table><tr><td> </td><td><pre class="example">> cat tstfil
this is a test
</pre></td></tr></table>
<p>However, ‘<tt>tstfil</tt>’ is not yet accessible using the symbolic link:
</p><table><tr><td> </td><td><pre class="example">> cat x
cat: x: No such file or directory
</pre></td></tr></table>
<p>In order to make ‘<tt>tstfil</tt>’ accessible using the link, you have to
destroy the link, and remake it:
</p><table><tr><td> </td><td><pre class="example">> rm x
/bin/rm: remove `x'? y
> ln -s tstfil x
> ls -l
total 1
pr--r--r-- 1 alknaff sirac 15 Feb 25 19:40 tstfil
lrwxrwxrwx 1 alknaff sirac 8 Feb 25 19:44 x -> tstfil
> cat x
this is a test
</pre></td></tr></table>
<hr size="6">
<a name="Hard-links"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Symbolic-links" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#How-it-works" title="Next section in reading order"> > </a>]</td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Using-zlibc" title="Beginning of this chapter or previous chapter"> << </a>]</td>
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<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Introduction" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Variable-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<h3 class="subsection">3.1.2 Hard links</h3>
<p>If you compress datafiles with hard links pointing to them, gzip refuses
to compress them.
</p>
<table><tr><td> </td><td><pre class="example">> echo 'this is a test' >tstfil
> ln tstfil x
> ls -li
total 2
166 -rw-r--r-- 2 alknaff sirac 15 Feb 25 19:46 tstfil
166 -rw-r--r-- 2 alknaff sirac 15 Feb 25 19:46 x
> gzip tstfil
gzip: tstfil has 1 other link -- unchanged
</pre></td></tr></table>
<p>Thus you need to remove these hard links first, and remake them after
compressing the file.
</p>
<table><tr><td> </td><td><pre class="example">> rm x
/bin/rm: remove `x'? y
> gzip tstfil
> ln tstfil x
> ls -li
total 2
167 pr--r--r-- 2 alknaff sirac 15 Feb 25 19:46 tstfil
167 pr--r--r-- 2 alknaff sirac 15 Feb 25 19:46 x
> cat x
this is a test
</pre></td></tr></table>
<hr size="6">
<a name="How-it-works"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Hard-links" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#Customization" title="Next section in reading order"> > </a>]</td>
<td valign="middle" align="left"> </td>
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<td valign="middle" align="left">[<a href="#Customization" title="Next chapter"> >> </a>]</td>
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<td valign="middle" align="left">[<a href="#Introduction" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
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</tr></table>
<a name="How-it-works-1"></a>
<h1 class="chapter">4. How it works</h1>
<p>Usually, programs don’t make system calls directly, but instead call a
library function which performs the actual system calls. For instance,
to open a file, the program first calls the <code>open</code> library
function, and then this function makes the actual syscall. Zlibc
overrides the <code>open</code> function and other related functions in order
to do the uncompression on the fly.
</p>
<p>If the <code>open</code> system call fails because the file doesn’t exist,
zlibc constructs the filename of a compressed file by appending
<code>.gz</code> to the filename supplied by the user program. If this
compressed file exists, it is opened and piped trough <code>gunzip</code>, and
the descriptor of the read end of this pipe is returned to the caller.
</p>
<p>In some cases, the compressed file is first uncompressed into a
temporary file, and a read descriptor for this file is passed to the
caller. This is necessary if the caller wants to call <code>lseek</code> on
the file or <code>mmap</code> it. A description of data files for which using
temporary is necessary can be given in the configuration files
‘<tt>/usr/local/etc/zlibc.conf</tt>’ (‘<tt>/etc/zlibc.conf</tt>’ on
Linux)<a name="DOCF1" href="#FOOT1">(1)</a> and
‘<tt>~/.zlibrc</tt>’. See section <a href="#Configuration-files">Configuration files</a>, for a detailed description
of their syntax.
</p>
<p>Many user programs try to check the existence of a given file by other
system calls before actually opening it. That’s why zlibc also
overrides these system calls. If for example the user program tries to
stat a file, this call is also intercepted.
</p>
<p>The compressed file, which exists physically on the disk, is also called
’the real file’, and the uncompressed file, whose existence is only
simulated by zlibc is called ’the virtual file’.
</p>
<hr size="6">
<a name="Customization"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#How-it-works" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#Environmental-variables" title="Next section in reading order"> > </a>]</td>
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<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Customization-1"></a>
<h1 class="chapter">5. Customization</h1>
<a name="index-Customization"></a>
<p>The behavior of zlibc can be tailored using configuration files or
environment variables. This customization should normally not be needed,
as the compiled-in defaults are already pretty complete.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top"><a href="#Environmental-variables">5.1 Environmental variables</a></td><td> </td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top"><a href="#Configuration-files">5.2 Configuration files</a></td><td> </td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top"><a href="#Compiled_002din-defaults">5.3 Compiled-in defaults</a></td><td> </td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top"><a href="#Compile_002dtime-configuration">5.4 Compile-time configuration via GNU autoconf</a></td><td> </td><td align="left" valign="top">
</td></tr>
</table>
<hr size="6">
<a name="Environmental-variables"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Customization" title="Previous section in reading order"> < </a>]</td>
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<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Environmental-variables-1"></a>
<h2 class="section">5.1 Environmental variables</h2>
<p>Environmental variables come in two kinds: <em>switch</em> variables have
a boolean value and can only be turned on or off, whereas <em>string</em>
variables can have arbitrary strings as values.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top"><a href="#Switch-variables">5.1.1 Switch variables</a></td><td> </td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top"><a href="#String-variables">5.1.2 String variables</a></td><td> </td><td align="left" valign="top">
</td></tr>
</table>
<hr size="6">
<a name="Switch-variables"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Environmental-variables" title="Previous section in reading order"> < </a>]</td>
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Switch-variables-1"></a>
<h3 class="subsection">5.1.1 Switch variables</h3>
<a name="index-LD_005fZLIB_005fVERBOSE"></a>
<a name="index-debugging-zlibc"></a>
<a name="index-LD_005fZLIB_005fUNLINK"></a>
<a name="index-removing-files"></a>
<a name="index-preventing-accidental-removal-of-compressed-files-_0028env_002evar_002e_0029"></a>
<a name="index-LD_005fZLIB_005fDISABLE"></a>
<a name="index-LD_005fZLIB_005fREADDIR_005fCOMPR"></a>
<a name="index-showing-compressed-files-in-a-directory-listing-_0028env_002evar_002e_0029"></a>
<p>These variables represent a flag which can be turned on or off. If
their value is <code>on</code> or <code>1</code> they are turned on, if their value
is <code>off</code> or <code>0</code> they are turned off. All other values are
ignored. If the same flag can be turned on or off using config files,
the environmental variable always has the priority.
</p>
<dl compact="compact">
<dt> <code>LD_ZLIB_VERBOSE</code> </dt>
<dd><p>If this variable is turned on, informational messages are printed on
many operations of zlibc. Moreover, error messages are printed in order
to point out errors in the configuration files, if any. If this variable
is turned off, errors are silently ignored.
</p>
</dd>
<dt> <code>LD_ZLIB_UNLINK</code></dt>
<dd><p>If this variable is turned on, and if the user program tries to unlink a
virtual (uncompressed) file, zlibc translates this call into unlinking
the real file. If this variable is turned off, unlink calls on virtual
files are ignored.
</p>
</dd>
<dt> <code>LD_ZLIB_DISABLE</code></dt>
<dd><p>If this variable is turned on, zlibc is switched off.
</p>
</dd>
<dt> <code>LD_ZLIB_READDIR_COMPR</code></dt>
<dd><p>If this variable is turned on, the readdir function shows the real
(compressed) files instead of the virtual (uncompressed) files.
</p></dd>
</dl>
<hr size="6">
<a name="String-variables"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Switch-variables" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#Configuration-files" title="Next section in reading order"> > </a>]</td>
<td valign="middle" align="left"> </td>
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="String-variables-1"></a>
<h3 class="subsection">5.1.2 String variables</h3>
<a name="index-LD_005fZLIB_005fTMP"></a>
<a name="index-directory-for-temporary-files-_0028env_002evar_002e_0029"></a>
<a name="index-LD_005fZLIB_005fEXT"></a>
<a name="index-filename-extension-for-compressed-files-_0028env_002evar_002e_0029"></a>
<a name="index-LD_005fZLIB_005fUNCOMPRESSOR"></a>
<a name="index-command-line-for-the-uncompressing-program-_0028env_002evar_002e_0029"></a>
<a name="index-LD_005fZLIB_005fCONFFILE"></a>
<a name="index-location-of-the-configuration-file-_0028env_002evar_002e_0029"></a>
<p>These variables have a string value, which represent a file, a directory
or a command.
</p>
<dl compact="compact">
<dt> <code>LD_ZLIB_TMP</code></dt>
<dd><p>This is the name of the directory where the temporary uncompressed files are
put. The default is /tmp.
</p>
</dd>
<dt> <code>LD_ZLIB_EXT</code></dt>
<dd><p>This is the extension which is appended to a virtual file name in order
to obtain the real (compressed) file name. The default is <code>.gz</code>.
</p>
</dd>
<dt> <code>LD_ZLIB_UNCOMPRESSOR</code></dt>
<dd><p>This is the name of the program to be invoked to uncompress the data. Default
is <code>gzip -dc</code>.
</p>
</dd>
<dt> <code>LD_ZLIB_CONFFILE</code> </dt>
<dd><p>This is the name of an additional configuration file. If this variable
is defined and if the corresponding file exists, the configuration
described in this file overrides the configurations in ‘<tt>~/.zlibrc</tt>’
and in ‘<tt>/usr/local/etc/zlibc.conf</tt>’ (‘<tt>/etc/zlibc.conf</tt>’ on
Linux).
</p></dd>
</dl>
<hr size="6">
<a name="Configuration-files"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#String-variables" title="Previous section in reading order"> < </a>]</td>
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Configuration-files-1"></a>
<h2 class="section">5.2 Configuration files</h2>
<a name="index-Processing-order-of-configuration-file_002e"></a>
<p>To get its configuration, zlibc first looks into the file described by
the environment variable <code>LD_ZLIB_CONFFILE</code> (if any), then in
‘<tt>~/.zlibrc</tt>’ and finally in ‘<tt>/usr/local/etc/zlibc.conf</tt>’
(‘<tt>/etc/zlibc.conf</tt>’ on Linux <a name="DOCF2" href="#FOOT2">(2)</a>). If the desired information is found in neither of
these files, the compiled-in defaults are used. It is possible to
supply only part of the needed information in the configuration
files. In that case, the missing information is retrieved from the
compiled-in defaults. This allows you to have really small runtime
configuration files, which only list the differences between the desired
configuration and the compiled-in configuration.
</p>
<p>If an error occurs while parsing one of the configuration files, the
offending file is skipped, and the search continues with the next
file. However, no error message is printed unless the environmental
variable <code>LD_ZLIB_VERBOSE</code> is turned on (i.e. set to <code>1</code> or
to <code>on</code> ).
</p>
<p>If two files contain contradictory information, the information in the
file which is scanned first is retained (usually ‘<tt>~/.zlibrc</tt>’). If
any flags have been set or unset using environmental variables, these
settings override the flags specified in the configuration files.
</p>
<p>The configuration files are read by each process. For each process, they
are read at most once, at the time when zlibc is first used (attempt to
access a compressed file). Afterwards they are cached in the process’s
virtual memory. Thus, changing zlibc configuration files doesn’t
generally have any effect on already running processes.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top"><a href="#Overall-structure">5.2.1 Overall structure</a></td><td> </td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top"><a href="#Commands-section">5.2.2 Commands section</a></td><td> </td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top"><a href="#Class-section">5.2.3 Class section</a></td><td> </td><td align="left" valign="top">
</td></tr>
</table>
<hr size="6">
<a name="Overall-structure"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Configuration-files" title="Previous section in reading order"> < </a>]</td>
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Overall-structure-1"></a>
<h3 class="subsection">5.2.1 Overall structure</h3>
<a name="index-commands-section"></a>
<a name="index-class-section"></a>
<a name="index-Parsing-order-of-configuration-files_002e"></a>
<p>The zlibrc files consist of two sections: A <em>commands</em> section
(<a href="#Commands-line-flags">Available commands line flags</a>) and a <em>class definition</em> section
(<a href="#Class-section">Class section</a>).
</p>
<p>The commands section describes how zlibc should behave depending on
the executable that it was called from. Several commands are grouped
together into <em>command classe</em>.
</p>
<p>The class definition section describes how zlibc should behave depending
on the class of the command and the datafile opened.
</p>
<p>The configuration file may contain comments in both sections: a comment
starts with a hash (<code>#</code>) and stops at the end of the line.
</p>
<p>Dashes (<code>-</code>) and underbars (<code>_</code>) may be used indifferently in
all keywords.
</p>
<hr size="6">
<a name="Commands-section"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Overall-structure" title="Previous section in reading order"> < </a>]</td>
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<td valign="middle" align="left"> </td>
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<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Commands-section-1"></a>
<h3 class="subsection">5.2.2 Commands section</h3>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top"><a href="#Commands-section-syntax">5.2.2.1 General syntax of the commands section</a></td><td> </td><td align="left" valign="top"> What goes into the commands
section
</td></tr>
<tr><td align="left" valign="top"><a href="#Commands-line-flags">5.2.2.2 Available commands line flags</a></td><td> </td><td align="left" valign="top"> Which flags are available
</td></tr>
</table>
<hr size="6">
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<td valign="middle" align="left">[<a href="#Introduction" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="General-syntax-of-the-commands-section"></a>
<h4 class="subsubsection">5.2.2.1 General syntax of the commands section</h4>
<a name="index-commands-section-1"></a>
<p>The format for a line in the "commands" section is as follows:
</p>
<table><tr><td> </td><td><pre class="display"><code>commands "</code><var>cmd1</var><code>"</code> [ … <code>"</code><var>cmdn</var><code>"</code> ] <code>use</code> <var>flags</var> <code>"</code><var>class</var><code>"</code>
</pre></td></tr></table>
<p>In this line, the <var>cmd1</var> … <var>cmdn</var> are the basenames of the
programs (commands) for which this line should apply. The basename is
the name without the path, i.e. <code>ls</code> instead of
<code>/usr/bin/ls</code>. The command names should be enclosed in quotes. You
may also use the keyword <code>default</code> (without quotes) to match all
commands.
</p>
<p>The <var>flags</var> describe those aspects of zlibc’s behaviour that are
independant from the datafile which is being accessed. These flags come
in pairs. The flags need not to be listed on a single <code>commands</code>
line, they may occur in several places, even in several different
configuration files (for instance one in <code>/etc/zlibc.conf</code> and
another one in <code>~/.zlibrc</code>.
</p>
<p>If two contradictory flags are found in the configuration files, the one
which is seen first is taken.
</p>
<p>If on the other hand a certain flag is not found at all in the
configuration files, the compiled-in default for this flag is used. This
is usually the second flag of each pair, described below
(see section <a href="#Commands-line-flags">Available commands line flags</a>).
</p>
<p>These flags can all be overridden by environmental variables. When the
corresponding environmental variable is set to <code>1</code> or to <code>on</code>,
the first flag is used, when it is set to <code>0</code> or to <code>off</code>. If
the environmental variables is set to neither of these 4 values, it is
ignored).
</p>
<p>The <var>class</var> names the commands class that these commands belong to.
If, for a given command, two <code>commands</code> lines give different
classes, the one which is seen first is taken. No union of classes is
made, the classes are always treated as a whole. Thus, if you want to
make a change to a command class, you need to describe it in its
entirety.
</p>
<p>The following example says that the <code>tar</code>, <code>cpio</code>, <code>pax</code>,
<code>cp</code> and <code>mv</code> show compressed files in a directory listing
(<code>readdir_compr</code> flag), and are of class <code>generic_safe</code>.
</p><table><tr><td> </td><td><pre class="example">commands "tar" "cpio" "pax" "cp" "mv" use readdir_compr "generic_safe"
</pre></td></tr></table>
<p>The class <code>generic_safe</code> would then need to be described further in
the class section.
</p>
<hr size="6">
<a name="Commands-line-flags"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Commands-section-syntax" title="Previous section in reading order"> < </a>]</td>
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Available-commands-line-flags"></a>
<h4 class="subsubsection">5.2.2.2 Available commands line flags</h4>
<a name="index-disable"></a>
<a name="index-enable"></a>
<a name="index-readdir_005fcompr"></a>
<a name="index-readdir_005funcompr"></a>
<a name="index-verbose"></a>
<a name="index-silent"></a>
<a name="index-disabling-zlibc-_0028conf_002e-file_0029"></a>
<a name="index-showing-compressed-files-on-a-directory-listing-_0028conf_002e-file_0029"></a>
<a name="index-debugging-zlibc-1"></a>
<p>This section describes the flags which can be used on a <code>commands</code>
line. All these flags come in pairs.
</p>
<p>The table below describes each of these pairs. The first word in the
header of each item is the non-default flag, the second word is the
default flag, and the third word is the environmental variable by which
you can override the settings from the configuration files. If this
environmental variable is turned on (set to 1), the non-default (first)
flag is taken, if it is turned off (set to 0), the default (second) flag
is taken.
</p>
<dl compact="compact">
<dt> <code>disable / enable / LD_ZLIB_DISAB</code></dt>
<dd><p>The <code>disable</code> flag disables zlibc for the programs on this commands
line. This is useful for compression and uncompression utilities.
Without this flag, <code>gunzip</code> would not work anymore, because it
would think that the uncompressed file exists already, and it would
refuse to overwrite this file.
</p>
</dd>
<dt> <code>disable_child / enable_child / LD_ZLIB_DISAB_CHILD</code></dt>
<dd><p>The <code>disable_child</code> flag disables zlibc for the programs started by
programs on this commands line. This is implemented by removeing all
occurrences of <code>uncompress.so</code> from the LD_PRELOAD environment
variable. This function is useful for programs such as xemacs, in order
to make sure that all launched subprograms return results consistent
with emacs itself (directory listings, etc)
</p>
</dd>
<dt> <code>readdir_compr / readdir_uncompr / LD_ZLIB_READDIR</code></dt>
<dd><p>The readdir function shows the uncompressed files (i.e. with their
trailing <code>.gz</code> extension) when the <code>readdir_compr</code> flag is
set, and the compressed files otherwise.
</p>
</dd>
<dt> <code>verbose / silent / LD_ZLIB_VERBOSE</code></dt>
<dd><p>When <code>verbose</code> is set, zlibc prints informational messages.
</p>
</dd>
<dt> <code>unlink / no_unlink / LD_ZLIB_UNLINK</code></dt>
<dd><p>If the <code>unlink</code> flag is set, and if the user program tries to
unlink a virtual (uncompressed) file, the package translates this call
into unlinking the real file. If the <code>no_unlink</code> flag is set,
requests to unlink virtual (uncompressed) files are silently ignored.
</p>
</dd>
</dl>
<hr size="6">
<a name="Class-section"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Commands-line-flags" title="Previous section in reading order"> < </a>]</td>
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Class-section-1"></a>
<h3 class="subsection">5.2.3 Class section</h3>
<p>A command class<a name="DOCF3" href="#FOOT3">(3)</a> definition describes those
aspects of zlibc’s behavior that depend on the name of the datafile
which is being accessed. Command classes are identified by a name which
is matched against the <var>class</var> parameter from the commands. The
class name should be enclosed between quotes both in the commands line
and in the class definition.
</p>
<p>The class section contains descriptions of different command classes
(i.e descriptions how datafiles should be uncompressed). Each class
definition begins with a line of the following format:
</p>
<table><tr><td> </td><td><pre class="display"><code>class "</code><var>id</var><code>"</code>
</pre></td></tr></table>
<p>The class <var>id</var> is the same string as the one used in the commands
line. The remaining lines of a class definition are as follows:
</p><table><tr><td> </td><td><pre class="display">[ [ <var>criterion</var> ] [ <code>"</code><var>name</var><code>"</code> ]] <var>mode</var>
</pre></td></tr></table>
<p>The following example shows the definition of the class used for X-servers.
</p>
<table><tr><td> </td><td><pre class="example"># X uses tmp files in its own directories.
class "X"
subdir "/usr/X11R6" usetmpfile
subdir "/usr/X386" usetmpfile
subdir "/usr/lib/X11" usetmpfile
showpipe
</pre></td></tr></table>
<p>This says that all compressed files who are in a subdirectory below
‘<tt>/usr/X11R6</tt>’, ‘<tt>/usr/X386</tt>’ or ‘<tt>/usr/lib/X11</tt>’ are
decompressed using temporary files (<code>usetmpfile</code>), and that files
from other directories are decompressed using pipes (<code>showpipe</code>)
</p>
<p>The following examples illustrates a command class, named <code>nopipe</code>,
which always uses temporary files for decompression
</p><table><tr><td> </td><td><pre class="display"># generic class which uses temp files for all files.
class "nopipe"
usetmpfile
</pre></td></tr></table>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top"><a href="#Criteria">5.2.3.1 File selection Criteria</a></td><td> </td><td align="left" valign="top"> To which data files does this line apply
</td></tr>
<tr><td align="left" valign="top"><a href="#Mode">5.2.3.2 Mode</a></td><td> </td><td align="left" valign="top"> How zlibc behaves for the files matching the
criterion
</td></tr>
</table>
<hr size="6">
<a name="Criteria"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Class-section" title="Previous section in reading order"> < </a>]</td>
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</tr></table>
<a name="File-selection-Criteria"></a>
<h4 class="subsubsection">5.2.3.1 File selection Criteria</h4>
<a name="index-directory-_0028selection-criterion_0029"></a>
<a name="index-filename-_0028selection-criterion_0029"></a>
<a name="index-extension-_0028selection-criterion_0029"></a>
<a name="index-suffix-_0028selection-criterion_0029"></a>
<a name="index-basename-_0028selection-criterion_0029"></a>
<a name="index-doublespaced-DOS-filesystem"></a>
<p>The <var>criterion </var> describes what parts of the filename should match:
</p>
<dl compact="compact">
<dt> <code>filename</code></dt>
<dd><p>The entire filename of the target data file must match
<var>name</var>.
</p>
</dd>
<dt> <code>basename</code></dt>
<dd><p>The basename (filename without directory) of the target data file must
match <var>name</var>.
</p>
</dd>
<dt> <code>directory</code></dt>
<dd><p>The data file must live in the directory <var>name</var>. If the user
program opens the file with an absolute pathname, that filename is used
as is. If on the other hand the user program uses a relative pathname,
zlibc uses the most direct path to the file (i.e. without symlinks).
</p>
</dd>
<dt> <code>subdirectory</code></dt>
<dd><p>The data file must live in the directory <var>name</var> or in one of its
subdirectories. If the user program opens the file with an absolute
pathname, that filename is used as is. If on the other hand the user
program uses a relative pathname, zlibc uses the most direct path to the
file (i.e. without symlinks).
</p>
</dd>
<dt> <code>suffix</code></dt>
<dd><p>The data file’s name must end in <var>name</var>. This is useful for
selecting files according to their extension.
</p>
</dd>
<dt> <code>filesystem</code></dt>
<dd><p>The data file must live on the same filesystem as <var>name</var>. This
criterion can for example be used for example to disable zlibc on a
doublespaced filesystem (where zlibc would be redundant), or to switch
off uncompressed size reporting on an <code>ftpfs</code> filesystems
<a name="DOCF4" href="#FOOT4">(4)</a>.
</p>
</dd>
<dt> <code>default</code></dt>
<dd><p>All data files match. All class definitions must have a default line,
and this default line must be the last line of the definition. The
default criterion needs no ’name’ parameter.
</p>
</dd>
<dt> <code>all</code></dt>
<dd><p>All data files match. Unlike <code>default</code>, this line needs not to be
the last line of the class definitions. Thus it is possible to specify
several <code>all</code> lines for different aspects of <code>zlibc</code>
behaviour.
</p></dd>
</dl>
<p>The lines of each class definition are scanned in sequence, and, for
each aspect<a name="DOCF5" href="#FOOT5">(5)</a>, the first matching line is
adopted. The class may be defined in another initialisation file, if
this file is scanned later. The <var>criterion</var> parameter may be omitted
if it can be deduced from the <var>name</var>. In that case, the following
heuristics are used:
</p>
<ul>
<li>
<var>Name</var>s beginning with a dot are considered as <code>suffix</code>.
</li><li>
<var>Name</var>s beginning with a slash, but not ending with a slash are
considered as <var>filename</var>.
</li><li>
<var>Name</var>s beginning and ending with a slash are considered as
<code>subdirectory</code>.
</li><li>
A missing <var>name</var> is considered as <code>default</code>.
</li><li>
All the other <var>name</var>s are considered as <code>basename</code>.
</li></ul>
<p><code>filesystem</code> criteria, because these tend to be more predictable.
</p>
<hr size="6">
<a name="Mode"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Criteria" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#Readonly" title="Next section in reading order"> > </a>]</td>
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</tr></table>
<a name="Mode-1"></a>
<h4 class="subsubsection">5.2.3.2 Mode</h4>
<p>The <var>mode</var> describes the behavior of zlibc in certain
situations. These are:
</p><ol>
<li>
What to do when a file is accessed in readonly mode.
</li><li>
What to do when a user program tries to append data to an existing file.
</li><li>
What to do when a user program tries to create a new file.
</li><li>
What to do when a user program tries to access an existing file and none
of the preceding situations apply (see section <a href="#Write">Other write requests</a>).
</li><li>
Whether to show the size of the uncompressed file or the size of the
compressed file as a response to stat (see section <a href="#Size">Size shown for compressed files</a>).
</li></ol>
<p>The mode for each off these 5 situations has to be described separately.
For each of these 5 situations, the scan through the class description
is done until the reaction of zlibc for this situation is defined.
</p>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top"><a href="#Readonly">Reaction to a readonly request</a></td><td> </td><td align="left" valign="top"> Behavior for programs wanting to only read files
</td></tr>
<tr><td align="left" valign="top"><a href="#Append">Reaction to an append request</a></td><td> </td><td align="left" valign="top"> - for programs wanting to add more data to
existing files
</td></tr>
<tr><td align="left" valign="top"><a href="#Creation">Reaction to a file creation request</a></td><td> </td><td align="left" valign="top"> - for programs wanting to create new files
</td></tr>
<tr><td align="left" valign="top"><a href="#Write">Other write requests</a></td><td> </td><td align="left" valign="top"> - for programs wanting to apply other
modifications to files
</td></tr>
<tr><td align="left" valign="top"><a href="#Size">Size shown for compressed files</a></td><td> </td><td align="left" valign="top"> - for programs wanting to know the size of a
file
</td></tr>
</table>
<hr size="6">
<a name="Readonly"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Mode" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#Append" title="Next section in reading order"> > </a>]</td>
<td valign="middle" align="left"> </td>
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<td valign="middle" align="left">[<a href="#Porting-zlibc" title="Next chapter"> >> </a>]</td>
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<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Introduction" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Variable-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Reaction-to-a-readonly-request"></a>
<h4 class="unnumberedsubsubsec">Reaction to a readonly request</h4>
<p>The reaction to a <code>readonly</code> request may be one of the following:
</p>
<dl compact="compact">
<dt> <code>show-pipe</code></dt>
<dd><p>The uncompressed data file is sent to the user program using a
pipe. This consumes very few resources, and it allows the decompression
to run in paralell with the user process, but it has the disadvantage
that the user program cannot use lseek. To warn the user program of
this, the data file is shown as a named pipe (FIFO) when it is
stat’ed.
</p>
</dd>
<dt> <code>use-tmp-file</code></dt>
<dd><p>This is the default setting. The data is uncompressed and put into a
temporary file. The user programs then reads its data from the temporary
file. This has the advantage that the user program may lseek, and the
disadvantage that more disk space is consumed, while the programming is
accessing the file.
</p>
</dd>
<dt> <code>hide-pipe</code></dt>
<dd><p>The data is sent through a pipe, but the file is shown as a regular file
("hidden") to the user program when it stats it. This might be needed
for programs which are picky about a file type, but who actually don’t
need lseek.
</p>
</dd>
<dt> <code>leave-compressed</code></dt>
<dd><p>The virtual (uncompressed) file is shown as non-existent to stat, and
readdir shows the physical (compressed) file. For certain programs, this
is enough to disable zlibc on a file per file basis. This is useful, for
example, to make emacs use its own compression support (crypt.el)
instead of zlibc. Crypt.el is able to compress files when writing them
back, whereas zlibc isn’t able to do so. The <code>leave-compressed</code>
doesn’t work correctly with the <code>directory</code> and <code>subdirectory</code>
criteria. Use the <code>filesystem</code> criterion instead.
</p>
</dd>
<dt> <code>dir-leave-compressed</code></dt>
<dd><p>The virtual (uncompressed) file is shown to stat, but readdir shows the
physical (compressed) file. This is useful to tell zlibc that we prefer
working on the physical file, but without making access to the virtual
file impossible. The <code>dir-leave-compressed</code> doesn’t work with the
<code>dir</code> and <code>subdir</code> criteria. Use the <code>filesystem</code>
criterion instead.
</p>
</dd>
</dl>
<hr size="6">
<a name="Append"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Readonly" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#Creation" title="Next section in reading order"> > </a>]</td>
<td valign="middle" align="left"> </td>
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<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Introduction" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Variable-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Reaction-to-an-append-request"></a>
<h4 class="unnumberedsubsubsec">Reaction to an append request</h4>
<p>The reaction to an <code>append</code> request may be one of the following:
</p>
<dl compact="compact">
<dt> <code>append-compressed</code></dt>
<dd><p>When a user program tries to append data to a non-existant file, but the
corresponding compressed file exists, zlibc translates this request into
appending the compressed data to the compressed file.
</p>
<p><strong>WARNING-1:</strong>
</p>
<p>This works with gzip, and might not work with other (un)compressors!
This relies on gzip’s feature to consider a concatenation of compressed
files as a compression of concatenated files.
</p>
<p><strong>WARNING-2:</strong>
</p>
<p>This is only reliable if you can guarantee that the file is not accessed
by some other program while the first one has it still open, or that it
won’t be opened again (even by the same program) shortly after it has
been closed. Delays longer than a second should be ok. Don’t enable
<code>append-compressed</code> if you expect the file to be written to by
several programs at once.
</p>
</dd>
<dt> <code>no-append-compressed</code></dt>
<dd><p>Don’t append to a compressed file (the user program will get a file not
found error). This is the default behavior.
</p>
</dd>
</dl>
<hr size="6">
<a name="Creation"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Append" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#Write" title="Next section in reading order"> > </a>]</td>
<td valign="middle" align="left"> </td>
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<td valign="middle" align="left">[<a href="#Class-section" title="Up section"> Up </a>]</td>
<td valign="middle" align="left">[<a href="#Porting-zlibc" title="Next chapter"> >> </a>]</td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Introduction" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Variable-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Reaction-to-a-file-creation-request"></a>
<h4 class="unnumberedsubsubsec">Reaction to a file creation request</h4>
<p>The reaction to a <code>create</code> request may be one of the following:
</p>
<dl compact="compact">
<dt> <code>create-compressed</code></dt>
<dd><p>When a user program tries to create a new file whose name matches the
pattern, zlibc translates this request into creating a compressed
file. A file is considered to be created, if the <code>O_TRUNC</code> flag is
set, or if both <code>O_CREAT</code> and <code>O_EXCL</code> are set. This only
applies to files opened write-only.
</p>
<p><strong>WARNING-1:</strong>
</p>
<p>This is only reliable if you can guarantee that the newly
created file is not accessed by some other program while the first one
has it still open, or that it won’t be opened again (even by the same
program) shortly after it has been closed.
</p>
<p><strong>WARNING-2:</strong>
</p>
<p>This should not be used if you expect the program to seek in this
file.
</p>
</dd>
<dt> <code>no-create-compressed</code></dt>
<dd><p>Newly created files are created uncompressed. This is the default.
</p></dd>
</dl>
<hr size="6">
<a name="Write"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Creation" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#Size" title="Next section in reading order"> > </a>]</td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Customization" title="Beginning of this chapter or previous chapter"> << </a>]</td>
<td valign="middle" align="left">[<a href="#Class-section" title="Up section"> Up </a>]</td>
<td valign="middle" align="left">[<a href="#Porting-zlibc" title="Next chapter"> >> </a>]</td>
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<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Introduction" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Variable-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Other-write-requests"></a>
<h4 class="unnumberedsubsubsec">Other write requests</h4>
<p>The reaction to other <code>write</code> requests may be one of the following:
</p>
<dl compact="compact">
<dt> <code>uncompress-before-write</code></dt>
<dd><p>When a user program tries to write to a non-existing file, and when a
compressed file with a corresponding name exists, this file is
uncompressed in place (i.e. having the same name, but without the .gz
extension)
</p>
<p><strong>WARNING-1:</strong>
</p>
<p>This is only safe when you can guarantee that the file is not opened by
several programs at once. However, once the call to the open function
has returned, other programs may open this file safely. If a second
program tries to open the file during the open call of the first, this
second program gets a permission error.
</p>
<p><strong>WARNING-2:</strong>
</p>
<p>When using this option, be careful when opening files belonging to
another user, or files living in a directory where you have no write
access to. Using this option in a directory without write access will
result in a permission error. Using this option in a directory where you
do have write access will change the ownership of the file to you, even
if it belonged to another user initially.
</p>
</dd>
<dt> <code>no-uncompress-before-write</code></dt>
<dd><p>Compressed files are not uncompressed before writing to them, and zlibc
returns a "file not found" error. This is the default.
</p>
</dd>
</dl>
<p>If several of these options apply for the same file,
<code>create-compressed</code> has priority over <code>append-compressed</code>
which has priority over <code>uncompress-before-write</code>.
</p>
<hr size="6">
<a name="Size"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Write" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[<a href="#Compiled_002din-defaults" title="Next section in reading order"> > </a>]</td>
<td valign="middle" align="left"> </td>
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<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Introduction" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Variable-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Size-shown-for-compressed-files"></a>
<h4 class="unnumberedsubsubsec">Size shown for compressed files</h4>
<a name="index-find"></a>
<a name="index-size-of-compressed-files"></a>
<a name="index-slowness-_0028of-find-due-to-reading-the-size_0029"></a>
<a name="index-show_002dcompressed_002dsize"></a>
<a name="index-ftpfs"></a>
<a name="index-ls-slowness-_0028on-an-ftpfs-filesystem_0029"></a>
<a name="index-slowness-_0028of-ls_002c-on-an-ftpfs-filesystem_0029"></a>
<a name="index-hanging-_0028of-ls_002c-on-an-ftpfs-filesystem_0029"></a>
<p>When an application calls <code>stat</code> to fetch the attributes of a file
(such as its permissions, size, type, etc.), zlibc stats the
corresponding compressed file instead. After doing so, zlibc has to
adjust some of the values returned by stat, such as the type and the
size. The type has to be adjusted for those files that should be shown
as pipes. The size has to be adjusted because user programs are usually
interested in the amount of data that they can actually read from the
file (i.e. the size of the uncompressed file) rather than the size of
the physical file (i.e. the size of the compressed file). However, in
order to find out the size of the uncompressed file, zlibc has to read
some data of the file, which may impact performance in situations where
many files are stat’ed. This is for instance the case for <code>find</code>,
or for <code>ls</code> on an <code>ftpfs</code> filesystem. The following two
behaviors of the stat call may be specified:
</p>
<dl compact="compact">
<dt> <code>show-compressed-size</code></dt>
<dd><p>Stat returns the size of the compressed file. This is less useful for
the application, but more efficient. If you mount any <code>ftpfs</code>
filesystems, you may switch on <code>show-compressed-size</code> just for that
filesystem by using the <code>filesystem</code> criterion (see section <a href="#Criteria">File selection Criteria</a>).
</p>
</dd>
<dt> <code>show-uncompressed-size</code></dt>
<dd><p>Stat returns the size of the uncompressed file. This is more useful for
the application, but less efficient. This is the default behavior.
</p>
</dd>
</dl>
<hr size="6">
<a name="Compiled_002din-defaults"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Size" title="Previous section in reading order"> < </a>]</td>
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<td valign="middle" align="left">[<a href="#Introduction" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
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</tr></table>
<a name="Compiled_002din-defaults-1"></a>
<h2 class="section">5.3 Compiled-in defaults</h2>
<p>It is possible to operate zlibc entirely without configuration files.
In this case, it uses the <em>compiled-in defaults</em>. These are
generated at compile-time from the ‘<tt>zlibrc.sample</tt>’ file. This file
has the same syntax as the configuration files described above
(see section <a href="#Configuration-files">Configuration files</a>). If you want to change the compiled-in
defaults of zlibc, edit that file, and remake.
</p>
<hr size="6">
<a name="Compile_002dtime-configuration"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Compiled_002din-defaults" title="Previous section in reading order"> < </a>]</td>
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<td valign="middle" align="left">[<a href="#Introduction" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Compile_002dtime-configuration-via-GNU-autoconf"></a>
<h2 class="section">5.4 Compile-time configuration via GNU autoconf</h2>
<a name="index-configure-options"></a>
<a name="index-temporary-file-directory"></a>
<a name="index-directory-for-temporary-files"></a>
<a name="index-compile_002dtime-configuration"></a>
<p>Before it can be compiled, zlibc must be configured using the GNU
autoconf script <code>./configure</code>. In most circumstances, running
<code>./configure</code> without any parameters is enough. However, you may
customize zlibc using various options to <code>./configure</code>. The
following options are supported:
</p><dl compact="compact">
<dt> <code>--prefix <var>directory</var></code></dt>
<dd><p>Prefix used for any directories used by zlibc. By default, this is
‘<tt>/usr/local</tt>’. Zlibc is installed in ‘<tt>$prefix/lib</tt>’, looks for
its system wide configuration file in ‘<tt>$prefix/etc</tt>’. Man pages are
installed in ‘<tt>$prefix/man</tt>’, info pages in ‘<tt>$prefix/info</tt>’ etc.
On Linux, if you use zlibc via ‘<tt>/etc/ld.so.preload</tt>’, you should use
‘<tt>/</tt>’ as the prefix instead of the default ‘<tt>$prefix/lib</tt>’.
</p>
</dd>
<dt> <code>--sysconfdir <var>directory</var></code></dt>
<dd><p>Directory containing the system-wide configuration file
‘<tt>zlibc.conf</tt>’. By default, this is derived from <code>prefix</code> (see
above).
</p>
</dd>
<dt> <code>--disable-runtime-conf</code></dt>
<dd><p>Disables run time configuration via environmental variables and via the
configuration files. This may be needed in hyper secure environments.
</p>
</dd>
<dt> <code>--disable-env-conf</code></dt>
<dd><p>Disables run time configuration via environmental variables
</p>
</dd>
<dt> <code>--disable-have-proc</code></dt>
<dd><p>Tells zlibc not to use the /proc filesystem to find out the commandline
of the programs for which it runs, even if a working /proc is detected.
</p>
</dd>
<dt> <code>--disable-have-proc</code></dt>
<dd><p>Tells zlibc to use the /proc filesystem to find out the commandline of
the programs for which it runs, even if no working /proc is detected.
</p>
</dd>
<dt> <code>--with-compr-ext=<var>extension</var></code></dt>
<dd><p>Uses <var>extension</var> as the filename extension of compressed files. By
default, is <code>.gz</code>
</p>
</dd>
<dt> <code>--with-extlen=<var>length</var></code></dt>
<dd><p>Allows to configure compressed filename extensions with at most
<var>length</var> character via runtime configuration. By default is 5.
</p>
</dd>
<dt> <code>--with-tmpdir=<var>directory</var></code></dt>
<dd><p>Uses <var>directory</var> to store the uncompressed files. By default is
<code>/tmp</code>.
</p>
</dd>
<dt> <code>--with-uncompressor=<var>uncompressor-command-line</var></code></dt>
<dd><p>Defines how the program for uncompressing files should be invoked. This
command should read the compressed file from stdin, and output the
uncompressed data to stdout By default is <code>gzip -dc</code>.
</p>
</dd>
</dl>
<p>In addition to the above-listed options, the standard GNU autoconf
options apply. Type <code>./configure --help</code> to get a complete list of
these.
</p>
<hr size="6">
<a name="Porting-zlibc"></a>
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<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Porting-zlibc-1"></a>
<h1 class="chapter">6. Porting zlibc</h1>
<p>Zlibc has been tested on three variants of Unix so far: Linux, SunOs,
Solaris. On all three platforms, zlibc has been compiled using GNU make
and gcc. However, porting it to other platforms should be
straightforward as long as they verify both of the following conditions:
</p>
<ol>
<li>
The target platform should have shared library support. The default
Makefile links zlibc by supplying the flags <code>-nostdlib -shared</code> to
gcc in addition to the usual <code>CFLAGS</code>. If your target platform
needs different flags to make shared libraries, change the definition of
the variable <code>SHAREDCFLAGS</code> in the Makefile.
</li><li>
The target platform should supply a way to perform system calls
directly without going through the library functions. Indeed, this is
needed because we are redefining the library functions and thus the
default functions become unavailable.
<p>Usually direct syscalls done by calling the syscall function. For
instance, in order to perform <code>open("test", O_RDONLY)</code> directly,
<code>sycall(SYS_open, "test", O_RDONLY)</code> is called.
</p>
<p>If your target platform uses a different way to perform direct
system calls, you need to supply different definitions for the real_xxx
functions in direct_sys.h. This is the case for AIX.
</p></li><li>
The target platform should provide a way to instruct the dynamic linker
to preload programs with extra object files not present in the shared
library. Any symbols defined in that object file override equivalent
symbols from libc. Usually this is done by pointing the
<code>LD_PRELOAD</code> variable to the object file to be used.
Unfortunately, I have found no way to achieve this on AIX. Any ideas
about how to do this are welcome.
</li></ol>
<p>Many platforms, including Solaris, provide several aliases for their
syscall stubs. It would be interesting to leave one of them alone, and
use it as a "direct syscall" stub, but unfortunately, it turns out that
in sometimes both stubs are used by the library! Thus, what would be an
advantage, becomes actually a disadvantage, because we will need to
override these aliases in addition to the canonical names. This is done
in altnames.c. Change it as needed. In order to know the names of
these aliases, try the following command: <code>nm /lib/libc.so | grep
lstat</code>. This lists any library symbols with <code>unlink</code> in their
name, which could be aliases.
</p>
<p>If you have successfully ported zlibc to a new platform, could you drop
me a note, so that I can include support for that platform in my next
release. Thanks
</p>
<hr size="6">
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<a name="Variable-index"></a>
<h1 class="unnumbered">Variable index</h1>
<table><tr><th valign="top">Jump to: </th><td><a href="#Variable-index_vr_letter-D" class="summary-letter"><b>D</b></a>
<a href="#Variable-index_vr_letter-E" class="summary-letter"><b>E</b></a>
<a href="#Variable-index_vr_letter-L" class="summary-letter"><b>L</b></a>
<a href="#Variable-index_vr_letter-R" class="summary-letter"><b>R</b></a>
<a href="#Variable-index_vr_letter-S" class="summary-letter"><b>S</b></a>
<a href="#Variable-index_vr_letter-V" class="summary-letter"><b>V</b></a>
</td></tr></table>
<table border="0" class="index-vr">
<tr><td></td><th align="left">Index Entry</th><th align="left"> Section</th></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Variable-index_vr_letter-D">D</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-disable"><code>disable</code></a></td><td valign="top"><a href="#Commands-line-flags">5.2.2.2 Available commands line flags</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Variable-index_vr_letter-E">E</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-enable"><code>enable</code></a></td><td valign="top"><a href="#Commands-line-flags">5.2.2.2 Available commands line flags</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Variable-index_vr_letter-L">L</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-LD_005fPRELOAD"><code>LD_PRELOAD</code></a></td><td valign="top"><a href="#Installing-zlibc">2. Installing zlibc</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-LD_005fZLIB_005fCONFFILE"><code>LD_ZLIB_CONFFILE</code></a></td><td valign="top"><a href="#String-variables">5.1.2 String variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-LD_005fZLIB_005fDISABLE"><code>LD_ZLIB_DISABLE</code></a></td><td valign="top"><a href="#Switch-variables">5.1.1 Switch variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-LD_005fZLIB_005fEXT"><code>LD_ZLIB_EXT</code></a></td><td valign="top"><a href="#String-variables">5.1.2 String variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-LD_005fZLIB_005fREADDIR_005fCOMPR"><code>LD_ZLIB_READDIR_COMPR</code></a></td><td valign="top"><a href="#Switch-variables">5.1.1 Switch variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-LD_005fZLIB_005fTMP"><code>LD_ZLIB_TMP</code></a></td><td valign="top"><a href="#String-variables">5.1.2 String variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-LD_005fZLIB_005fUNCOMPRESSOR"><code>LD_ZLIB_UNCOMPRESSOR</code></a></td><td valign="top"><a href="#String-variables">5.1.2 String variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-LD_005fZLIB_005fUNLINK"><code>LD_ZLIB_UNLINK</code></a></td><td valign="top"><a href="#Switch-variables">5.1.1 Switch variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-LD_005fZLIB_005fVERBOSE"><code>LD_ZLIB_VERBOSE</code></a></td><td valign="top"><a href="#Switch-variables">5.1.1 Switch variables</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Variable-index_vr_letter-R">R</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-readdir_005fcompr"><code>readdir_compr</code></a></td><td valign="top"><a href="#Commands-line-flags">5.2.2.2 Available commands line flags</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-readdir_005funcompr"><code>readdir_uncompr</code></a></td><td valign="top"><a href="#Commands-line-flags">5.2.2.2 Available commands line flags</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Variable-index_vr_letter-S">S</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-show_002dcompressed_002dsize"><code>show-compressed-size</code></a></td><td valign="top"><a href="#Size">Size shown for compressed files</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-silent"><code>silent</code></a></td><td valign="top"><a href="#Commands-line-flags">5.2.2.2 Available commands line flags</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Variable-index_vr_letter-V">V</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-verbose"><code>verbose</code></a></td><td valign="top"><a href="#Commands-line-flags">5.2.2.2 Available commands line flags</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
</table>
<table><tr><th valign="top">Jump to: </th><td><a href="#Variable-index_vr_letter-D" class="summary-letter"><b>D</b></a>
<a href="#Variable-index_vr_letter-E" class="summary-letter"><b>E</b></a>
<a href="#Variable-index_vr_letter-L" class="summary-letter"><b>L</b></a>
<a href="#Variable-index_vr_letter-R" class="summary-letter"><b>R</b></a>
<a href="#Variable-index_vr_letter-S" class="summary-letter"><b>S</b></a>
<a href="#Variable-index_vr_letter-V" class="summary-letter"><b>V</b></a>
</td></tr></table>
<hr size="6">
<a name="Concept-Index"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Variable-Index" title="Previous section in reading order"> < </a>]</td>
<td valign="middle" align="left">[ > ]</td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Variable-Index" title="Beginning of this chapter or previous chapter"> << </a>]</td>
<td valign="middle" align="left">[<a href="#Introduction" title="Up section"> Up </a>]</td>
<td valign="middle" align="left">[ >> ]</td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left"> </td>
<td valign="middle" align="left">[<a href="#Introduction" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Variable-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<a name="Concept-index"></a>
<h1 class="unnumbered">Concept index</h1>
<table><tr><th valign="top">Jump to: </th><td><a href="#Concept-index_cp_letter-A" class="summary-letter"><b>A</b></a>
<a href="#Concept-index_cp_letter-B" class="summary-letter"><b>B</b></a>
<a href="#Concept-index_cp_letter-C" class="summary-letter"><b>C</b></a>
<a href="#Concept-index_cp_letter-D" class="summary-letter"><b>D</b></a>
<a href="#Concept-index_cp_letter-E" class="summary-letter"><b>E</b></a>
<a href="#Concept-index_cp_letter-F" class="summary-letter"><b>F</b></a>
<a href="#Concept-index_cp_letter-H" class="summary-letter"><b>H</b></a>
<a href="#Concept-index_cp_letter-I" class="summary-letter"><b>I</b></a>
<a href="#Concept-index_cp_letter-L" class="summary-letter"><b>L</b></a>
<a href="#Concept-index_cp_letter-M" class="summary-letter"><b>M</b></a>
<a href="#Concept-index_cp_letter-P" class="summary-letter"><b>P</b></a>
<a href="#Concept-index_cp_letter-R" class="summary-letter"><b>R</b></a>
<a href="#Concept-index_cp_letter-S" class="summary-letter"><b>S</b></a>
<a href="#Concept-index_cp_letter-T" class="summary-letter"><b>T</b></a>
</td></tr></table>
<table border="0" class="index-cp">
<tr><td></td><th align="left">Index Entry</th><th align="left"> Section</th></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Concept-index_cp_letter-A">A</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-ALPHA-patches">ALPHA patches</a></td><td valign="top"><a href="#Introduction">Introduction</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Concept-index_cp_letter-B">B</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-basename-_0028selection-criterion_0029">basename (selection criterion)</a></td><td valign="top"><a href="#Criteria">5.2.3.1 File selection Criteria</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-Boot-problems">Boot problems</a></td><td valign="top"><a href="#Installing-zlibc">2. Installing zlibc</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-bugs">bugs</a></td><td valign="top"><a href="#Introduction">Introduction</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Concept-index_cp_letter-C">C</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-class-section">class section</a></td><td valign="top"><a href="#Overall-structure">5.2.1 Overall structure</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-command-line-for-the-uncompressing-program-_0028env_002evar_002e_0029">command line for the uncompressing program (env.var.)</a></td><td valign="top"><a href="#String-variables">5.1.2 String variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-commands-section">commands section</a></td><td valign="top"><a href="#Overall-structure">5.2.1 Overall structure</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-commands-section-1">commands section</a></td><td valign="top"><a href="#Commands-section-syntax">5.2.2.1 General syntax of the commands section</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-compile_002dtime-configuration">compile-time configuration</a></td><td valign="top"><a href="#Compile_002dtime-configuration">5.4 Compile-time configuration via GNU autoconf</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-configure-options">configure options</a></td><td valign="top"><a href="#Compile_002dtime-configuration">5.4 Compile-time configuration via GNU autoconf</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-Customization">Customization</a></td><td valign="top"><a href="#Customization">5. Customization</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Concept-index_cp_letter-D">D</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-debugging-zlibc">debugging zlibc</a></td><td valign="top"><a href="#Switch-variables">5.1.1 Switch variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-debugging-zlibc-1">debugging zlibc</a></td><td valign="top"><a href="#Commands-line-flags">5.2.2.2 Available commands line flags</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-diffs">diffs</a></td><td valign="top"><a href="#Introduction">Introduction</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-directory-_0028selection-criterion_0029">directory (selection criterion)</a></td><td valign="top"><a href="#Criteria">5.2.3.1 File selection Criteria</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-directory-for-temporary-files">directory for temporary files</a></td><td valign="top"><a href="#Compile_002dtime-configuration">5.4 Compile-time configuration via GNU autoconf</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-directory-for-temporary-files-_0028env_002evar_002e_0029">directory for temporary files (env.var.)</a></td><td valign="top"><a href="#String-variables">5.1.2 String variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-disabling-zlibc-_0028conf_002e-file_0029">disabling zlibc (conf. file)</a></td><td valign="top"><a href="#Commands-line-flags">5.2.2.2 Available commands line flags</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-doublespaced-DOS-filesystem">doublespaced DOS filesystem</a></td><td valign="top"><a href="#Criteria">5.2.3.1 File selection Criteria</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Concept-index_cp_letter-E">E</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-extension-_0028selection-criterion_0029">extension (selection criterion)</a></td><td valign="top"><a href="#Criteria">5.2.3.1 File selection Criteria</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Concept-index_cp_letter-F">F</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-filename-_0028selection-criterion_0029">filename (selection criterion)</a></td><td valign="top"><a href="#Criteria">5.2.3.1 File selection Criteria</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-filename-extension-for-compressed-files-_0028env_002evar_002e_0029">filename extension for compressed files (env.var.)</a></td><td valign="top"><a href="#String-variables">5.1.2 String variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-find">find</a></td><td valign="top"><a href="#Size">Size shown for compressed files</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-ftpfs">ftpfs</a></td><td valign="top"><a href="#Size">Size shown for compressed files</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Concept-index_cp_letter-H">H</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-hanging-_0028of-ls_002c-on-an-ftpfs-filesystem_0029">hanging (of ls, on an ftpfs filesystem)</a></td><td valign="top"><a href="#Size">Size shown for compressed files</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Concept-index_cp_letter-I">I</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-Installation">Installation</a></td><td valign="top"><a href="#Installing-zlibc">2. Installing zlibc</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Concept-index_cp_letter-L">L</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-location-of-the-configuration-file-_0028env_002evar_002e_0029">location of the configuration file (env.var.)</a></td><td valign="top"><a href="#String-variables">5.1.2 String variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-ls-slowness-_0028on-an-ftpfs-filesystem_0029">ls slowness (on an ftpfs filesystem)</a></td><td valign="top"><a href="#Size">Size shown for compressed files</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Concept-index_cp_letter-M">M</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-mailing-list">mailing list</a></td><td valign="top"><a href="#Introduction">Introduction</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Concept-index_cp_letter-P">P</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-Parsing-order-of-configuration-files_002e">Parsing order of configuration files.</a></td><td valign="top"><a href="#Overall-structure">5.2.1 Overall structure</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-patches">patches</a></td><td valign="top"><a href="#Introduction">Introduction</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-preventing-accidental-removal-of-compressed-files-_0028env_002evar_002e_0029">preventing accidental removal of compressed files (env.var.)</a></td><td valign="top"><a href="#Switch-variables">5.1.1 Switch variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-Processing-order-of-configuration-file_002e">Processing order of configuration file.</a></td><td valign="top"><a href="#Configuration-files">5.2 Configuration files</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Concept-index_cp_letter-R">R</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-removing-files">removing files</a></td><td valign="top"><a href="#Switch-variables">5.1.1 Switch variables</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Concept-index_cp_letter-S">S</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-Set_002duid-programs">Set-uid programs</a></td><td valign="top"><a href="#Installing-zlibc">2. Installing zlibc</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-showing-compressed-files-in-a-directory-listing-_0028env_002evar_002e_0029">showing compressed files in a directory listing (env.var.)</a></td><td valign="top"><a href="#Switch-variables">5.1.1 Switch variables</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-showing-compressed-files-on-a-directory-listing-_0028conf_002e-file_0029">showing compressed files on a directory listing (conf. file)</a></td><td valign="top"><a href="#Commands-line-flags">5.2.2.2 Available commands line flags</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-size-of-compressed-files">size of compressed files</a></td><td valign="top"><a href="#Size">Size shown for compressed files</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-slowness-_0028of-find-due-to-reading-the-size_0029">slowness (of find due to reading the size)</a></td><td valign="top"><a href="#Size">Size shown for compressed files</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-slowness-_0028of-ls_002c-on-an-ftpfs-filesystem_0029">slowness (of ls, on an ftpfs filesystem)</a></td><td valign="top"><a href="#Size">Size shown for compressed files</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-suffix-_0028selection-criterion_0029">suffix (selection criterion)</a></td><td valign="top"><a href="#Criteria">5.2.3.1 File selection Criteria</a></td></tr>
<tr><td></td><td valign="top"><a href="#index-Symbolic-links">Symbolic links</a></td><td valign="top"><a href="#Using-zlibc">3. Using zlibc</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
<tr><th><a name="Concept-index_cp_letter-T">T</a></th><td></td><td></td></tr>
<tr><td></td><td valign="top"><a href="#index-temporary-file-directory">temporary file directory</a></td><td valign="top"><a href="#Compile_002dtime-configuration">5.4 Compile-time configuration via GNU autoconf</a></td></tr>
<tr><td colspan="3"> <hr></td></tr>
</table>
<table><tr><th valign="top">Jump to: </th><td><a href="#Concept-index_cp_letter-A" class="summary-letter"><b>A</b></a>
<a href="#Concept-index_cp_letter-B" class="summary-letter"><b>B</b></a>
<a href="#Concept-index_cp_letter-C" class="summary-letter"><b>C</b></a>
<a href="#Concept-index_cp_letter-D" class="summary-letter"><b>D</b></a>
<a href="#Concept-index_cp_letter-E" class="summary-letter"><b>E</b></a>
<a href="#Concept-index_cp_letter-F" class="summary-letter"><b>F</b></a>
<a href="#Concept-index_cp_letter-H" class="summary-letter"><b>H</b></a>
<a href="#Concept-index_cp_letter-I" class="summary-letter"><b>I</b></a>
<a href="#Concept-index_cp_letter-L" class="summary-letter"><b>L</b></a>
<a href="#Concept-index_cp_letter-M" class="summary-letter"><b>M</b></a>
<a href="#Concept-index_cp_letter-P" class="summary-letter"><b>P</b></a>
<a href="#Concept-index_cp_letter-R" class="summary-letter"><b>R</b></a>
<a href="#Concept-index_cp_letter-S" class="summary-letter"><b>S</b></a>
<a href="#Concept-index_cp_letter-T" class="summary-letter"><b>T</b></a>
</td></tr></table>
<hr size="6">
<a name="SEC_Foot"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Introduction" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Variable-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<h1>Footnotes</h1>
<h3><a name="FOOT1" href="#DOCF1">(1)</a></h3>
<p>Actually the location of the system-wide include file
depends on the settings of <code>sysconfdir</code> and <code>prefix</code> during
<code>./configure</code> (see section <a href="#Compile_002dtime-configuration">Compile-time configuration via GNU autoconf</a>).
</p><h3><a name="FOOT2" href="#DOCF2">(2)</a></h3>
<p>Actually the location of the
system-wide include file depends on the settings of <code>sysconfdir</code>
and <code>prefix</code> during <code>./configure</code> (see section <a href="#Compile_002dtime-configuration">Compile-time configuration via GNU autoconf</a>).
</p><h3><a name="FOOT3" href="#DOCF3">(3)</a></h3>
<p>These command classes are unrelated to the
classes in object oriented programming.
</p><h3><a name="FOOT4" href="#DOCF4">(4)</a></h3>
<p>uncompressed size reporting (see section <a href="#Size">Size shown for compressed files</a> would make <code>ls</code>
painfully slow on an <code>ftpfs</code> filesystem, as all files would have to
be downloaded before their size could be reported.
</p><h3><a name="FOOT5" href="#DOCF5">(5)</a></h3>
<p>See see section <a href="#Mode">Mode</a>
</p><hr size="1">
<a name="SEC_Contents"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Introduction" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Variable-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<h1>Table of Contents</h1>
<div class="contents">
<ul class="toc">
<li><a name="toc-Introduction" href="#Introduction">Introduction</a></li>
<li><a name="toc-Where-to-get-zlibc" href="#Location">1. Where to get zlibc</a></li>
<li><a name="toc-Installing-zlibc-1" href="#Installing-zlibc">2. Installing zlibc</a></li>
<li><a name="toc-Using-zlibc-1" href="#Using-zlibc">3. Using zlibc</a>
<ul class="toc">
<li><a name="toc-Zlibc-and-links" href="#Zlibc-and-links">3.1 Zlibc and links</a>
<ul class="toc">
<li><a name="toc-Symbolic-links" href="#Symbolic-links">3.1.1 Symbolic links</a></li>
<li><a name="toc-Hard-links" href="#Hard-links">3.1.2 Hard links</a></li>
</ul>
</li>
</ul></li>
<li><a name="toc-How-it-works-1" href="#How-it-works">4. How it works</a></li>
<li><a name="toc-Customization-1" href="#Customization">5. Customization</a>
<ul class="toc">
<li><a name="toc-Environmental-variables-1" href="#Environmental-variables">5.1 Environmental variables</a>
<ul class="toc">
<li><a name="toc-Switch-variables-1" href="#Switch-variables">5.1.1 Switch variables</a></li>
<li><a name="toc-String-variables-1" href="#String-variables">5.1.2 String variables</a></li>
</ul></li>
<li><a name="toc-Configuration-files-1" href="#Configuration-files">5.2 Configuration files</a>
<ul class="toc">
<li><a name="toc-Overall-structure-1" href="#Overall-structure">5.2.1 Overall structure</a></li>
<li><a name="toc-Commands-section-1" href="#Commands-section">5.2.2 Commands section</a>
<ul class="toc">
<li><a name="toc-General-syntax-of-the-commands-section" href="#Commands-section-syntax">5.2.2.1 General syntax of the commands section</a></li>
<li><a name="toc-Available-commands-line-flags" href="#Commands-line-flags">5.2.2.2 Available commands line flags</a></li>
</ul></li>
<li><a name="toc-Class-section-1" href="#Class-section">5.2.3 Class section</a>
<ul class="toc">
<li><a name="toc-File-selection-Criteria" href="#Criteria">5.2.3.1 File selection Criteria</a></li>
<li><a name="toc-Mode-1" href="#Mode">5.2.3.2 Mode</a></li>
<li><a name="toc-Reaction-to-a-readonly-request" href="#Readonly">Reaction to a readonly request</a></li>
<li><a name="toc-Reaction-to-an-append-request" href="#Append">Reaction to an append request</a></li>
<li><a name="toc-Reaction-to-a-file-creation-request" href="#Creation">Reaction to a file creation request</a></li>
<li><a name="toc-Other-write-requests" href="#Write">Other write requests</a></li>
<li><a name="toc-Size-shown-for-compressed-files" href="#Size">Size shown for compressed files</a></li>
</ul>
</li>
</ul></li>
<li><a name="toc-Compiled_002din-defaults-1" href="#Compiled_002din-defaults">5.3 Compiled-in defaults</a></li>
<li><a name="toc-Compile_002dtime-configuration-via-GNU-autoconf" href="#Compile_002dtime-configuration">5.4 Compile-time configuration via GNU autoconf</a></li>
</ul></li>
<li><a name="toc-Porting-zlibc-1" href="#Porting-zlibc">6. Porting zlibc</a></li>
<li><a name="toc-Variable-index" href="#Variable-Index">Variable index</a></li>
<li><a name="toc-Concept-index" href="#Concept-Index">Concept index</a></li>
</ul>
</div>
<hr size="1">
<a name="SEC_About"></a>
<table cellpadding="1" cellspacing="1" border="0">
<tr><td valign="middle" align="left">[<a href="#Introduction" title="Cover (top) of document">Top</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_Contents" title="Table of contents">Contents</a>]</td>
<td valign="middle" align="left">[<a href="#Variable-Index" title="Index">Index</a>]</td>
<td valign="middle" align="left">[<a href="#SEC_About" title="About (help)"> ? </a>]</td>
</tr></table>
<h1>About This Document</h1>
<p>
This document was generated by <em>Build Daemon</em> on <em>January 9, 2016</em> using <a href="http://www.nongnu.org/texi2html/"><em>texi2html 1.82</em></a>.
</p>
<p>
The buttons in the navigation panels have the following meaning:
</p>
<table border="1">
<tr>
<th> Button </th>
<th> Name </th>
<th> Go to </th>
<th> From 1.2.3 go to</th>
</tr>
<tr>
<td align="center"> [ < ] </td>
<td align="center">Back</td>
<td>Previous section in reading order</td>
<td>1.2.2</td>
</tr>
<tr>
<td align="center"> [ > ] </td>
<td align="center">Forward</td>
<td>Next section in reading order</td>
<td>1.2.4</td>
</tr>
<tr>
<td align="center"> [ << ] </td>
<td align="center">FastBack</td>
<td>Beginning of this chapter or previous chapter</td>
<td>1</td>
</tr>
<tr>
<td align="center"> [ Up ] </td>
<td align="center">Up</td>
<td>Up section</td>
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<tr>
<td align="center"> [ >> ] </td>
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</tr>
<tr>
<td align="center"> [Top] </td>
<td align="center">Top</td>
<td>Cover (top) of document</td>
<td> </td>
</tr>
<tr>
<td align="center"> [Contents] </td>
<td align="center">Contents</td>
<td>Table of contents</td>
<td> </td>
</tr>
<tr>
<td align="center"> [Index] </td>
<td align="center">Index</td>
<td>Index</td>
<td> </td>
</tr>
<tr>
<td align="center"> [ ? ] </td>
<td align="center">About</td>
<td>About (help)</td>
<td> </td>
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</table>
<p>
where the <strong> Example </strong> assumes that the current position is at <strong> Subsubsection One-Two-Three </strong> of a document of the following structure:
</p>
<ul>
<li> 1. Section One
<ul>
<li>1.1 Subsection One-One
<ul>
<li>...</li>
</ul>
</li>
<li>1.2 Subsection One-Two
<ul>
<li>1.2.1 Subsubsection One-Two-One</li>
<li>1.2.2 Subsubsection One-Two-Two</li>
<li>1.2.3 Subsubsection One-Two-Three
<strong><== Current Position </strong></li>
<li>1.2.4 Subsubsection One-Two-Four</li>
</ul>
</li>
<li>1.3 Subsection One-Three
<ul>
<li>...</li>
</ul>
</li>
<li>1.4 Subsection One-Four</li>
</ul>
</li>
</ul>
<hr size="1">
<p>
<font size="-1">
This document was generated by <em>Build Daemon</em> on <em>January 9, 2016</em> using <a href="http://www.nongnu.org/texi2html/"><em>texi2html 1.82</em></a>.
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