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| <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> | <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>libConfuse tutorial</title><link rel="stylesheet" type="text/css" href="tutorial.css" /><meta name="generator" content="DocBook XSL Stylesheets V1.79.1" /><link rel="home" href="index.html" title="libConfuse tutorial" /><link rel="next" href="ar01s02.html" title="2. Other types of options" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">libConfuse tutorial</th></tr><tr><td width="20%" align="left"> </td><th width="60%" align="center"> </th><td width="20%" align="right"> <a accesskey="n" href="ar01s02.html">Next</a></td></tr></table><hr /></div><div class="article"><div class="titlepage"><div><div><h2 class="title"><a id="idm1"></a>libConfuse tutorial</h2></div><div><div class="author"><h3 class="author"><span class="firstname">Martin</span> <span class="surname">Hedenfalk</span></h3></div></div></div><hr /></div><div class="toc"><p><strong>Table of Contents</strong></p><dl class="toc"><dt><span class="sect1"><a href="index.html#idm7">1. Introducing libConfuse in an existing program</a></span></dt><dd><dl><dt><span class="sect2"><a href="index.html#idm29">1.1. Environment variables in values</a></span></dt></dl></dd><dt><span class="sect1"><a href="ar01s02.html">2. Other types of options</a></span></dt><dt><span class="sect1"><a href="ar01s03.html">3. Introducing lists</a></span></dt><dt><span class="sect1"><a href="ar01s04.html">4. Using sections</a></span></dt><dt><span class="sect1"><a href="ar01s05.html">5. Parsing from internal buffers</a></span></dt><dt><span class="sect1"><a href="ar01s06.html">6. Validating callback functions</a></span></dt><dd><dl><dt><span class="sect2"><a href="ar01s06.html#idm126">6.1. Installing the callback</a></span></dt></dl></dd><dt><span class="sect1"><a href="ar01s07.html">7. Value parsing callback</a></span></dt><dt><span class="sect1"><a href="ar01s08.html">8. Functions</a></span></dt><dd><dl><dt><span class="sect2"><a href="ar01s08.html#idm145">8.1. Predefined functions</a></span></dt></dl></dd><dt><span class="sect1"><a href="ar01s09.html">9. Saving configuration files</a></span></dt><dd><dl><dt><span class="sect2"><a href="ar01s09.html#idm157">9.1. Altering the printing of certain options</a></span></dt></dl></dd></dl></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm7"></a>1. Introducing libConfuse in an existing program</h2></div></div></div><p>Consider this simple program:</p><a id="listing1"></a><pre class="programlisting"> |
| <html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968" /><title>libConfuse tutorial</title><link rel="stylesheet" href="tutorial.css" type="text/css" /><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="index.html" title="libConfuse tutorial" /><link rel="next" href="ar01s02.html" title="2. Other types of options" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">libConfuse tutorial</th></tr><tr><td width="20%" align="left"> </td><th width="60%" align="center"> </th><td width="20%" align="right"> <a accesskey="n" href="ar01s02.html">Next</a></td></tr></table><hr /></div><div class="article" title="libConfuse tutorial"><div class="titlepage"><div><div><h2 class="title"><a id="id433031"></a>libConfuse tutorial</h2></div><div><div class="author"><h3 class="author"><span class="firstname">Martin</span> <span class="surname">Hedenfalk</span></h3></div></div></div><hr /></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="index.html#id433064">1. Introducing libConfuse in an existing program</a></span></dt><dd><dl><dt><span class="sect2"><a href="index.html#id401812">1.1. Environment variables in values</a></span></dt></dl></dd><dt><span class="sect1"><a href="ar01s02.html">2. Other types of options</a></span></dt><dt><span class="sect1"><a href="ar01s03.html">3. Introducing lists</a></span></dt><dt><span class="sect1"><a href="ar01s04.html">4. Using sections</a></span></dt><dt><span class="sect1"><a href="ar01s05.html">5. Parsing from internal buffers</a></span></dt><dt><span class="sect1"><a href="ar01s06.html">6. Validating callback functions</a></span></dt><dd><dl><dt><span class="sect2"><a href="ar01s06.html#id442390">6.1. Installing the callback</a></span></dt></dl></dd><dt><span class="sect1"><a href="ar01s07.html">7. Value parsing callback</a></span></dt><dt><span class="sect1"><a href="ar01s08.html">8. Functions</a></span></dt><dd><dl><dt><span class="sect2"><a href="ar01s08.html#id442506">8.1. Predefined functions</a></span></dt></dl></dd><dt><span class="sect1"><a href="ar01s09.html">9. Saving configuration files</a></span></dt><dd><dl><dt><span class="sect2"><a href="ar01s09.html#id442560">9.1. Altering the printing of certain options</a></span></dt></dl></dd></dl></div><div class="sect1" title="1. Introducing libConfuse in an existing program"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="id433064"></a>1. Introducing libConfuse in an existing program</h2></div></div></div><p>Consider this simple program:</p><a id="listing1"></a><pre class="programlisting"> | |
| 1 #include <stdio.h> |
1 #include <stdio.h> |
| 2 |
2 |
| 3 int main(void) |
3 int main(void) |
|
Line 68 target = "Neighbour"
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Line 67 target = "Neighbour"
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| Thus, if no <code class="varname">target</code> option was specified in the |
Thus, if no <code class="varname">target</code> option was specified in the |
| configuration file, the hello program would have printed the |
configuration file, the hello program would have printed the |
| standard greeting "Hello, World". |
standard greeting "Hello, World". |
| </p><div class="sect2" title="1.1. Environment variables in values"><div class="titlepage"><div><div><h3 class="title"><a id="id401812"></a>1.1. Environment variables in values</h3></div></div></div><p> | </p><div class="sect2"><div class="titlepage"><div><div><h3 class="title"><a id="idm29"></a>1.1. Environment variables in values</h3></div></div></div><p> |
| What else can we do in the configuration file? We can set the value to an |
What else can we do in the configuration file? We can set the value to an |
| environment variable: |
environment variable: |
| </p><pre class="programlisting"> |
</p><pre class="programlisting"> |
|
Line 82 target = ${USER:-User}
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Line 81 target = ${USER:-User}
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| </pre><p> |
</pre><p> |
| Now, if the USER environment variable is unset, the string "User" will be |
Now, if the USER environment variable is unset, the string "User" will be |
| used instead. |
used instead. |
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