<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>Chapter 1. Introduction</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2"><link rel="home" href="index.html" title="SystemTap Tapset Reference Manual"><link rel="up" href="index.html" title="SystemTap Tapset Reference Manual"><link rel="prev" href="index.html" title="SystemTap Tapset Reference Manual"><link rel="next" href="ch02.html" title="Chapter 2. Context Functions"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 1. Introduction</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="index.html">Prev</a> </td><th width="60%" align="center"> </th><td width="20%" align="right"> <a accesskey="n" href="ch02.html">Next</a></td></tr></table><hr></div><div class="chapter" title="Chapter 1. Introduction"><div class="titlepage"><div><div><h2 class="title"><a name="introduction"></a>Chapter 1. Introduction</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="ch01.html#format">Tapset Name Format</a></span></dt></dl></div><p>
SystemTap provides free software (GPL) infrastructure to simplify the
gathering of information about the running Linux system. This assists
diagnosis of a performance or functional problem. SystemTap eliminates the
need for the developer to go through the tedious and disruptive instrument,
recompile, install, and reboot sequence that may be otherwise required to
collect data.
</p><p>
SystemTap provides a simple command line interface and scripting language
for writing instrumentation for a live running kernel. The instrumentation
makes extensive use of the probe points and functions provided in the
<em class="firstterm">tapset</em> library. This document describes the various
probe points and functions.
</p><div class="section" title="Tapset Name Format"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="format"></a>Tapset Name Format</h2></div></div></div><p>In this guide, tapset definitions appear in the following format:</p><pre class="screen">
name:return (parameters)
definition
</pre><p>
The <em class="replaceable"><code>return</code></em> field specifies what data type the
tapset extracts and returns from the kernel during a probe (and thus,
returns). Tapsets use 2 data types for
<em class="replaceable"><code>return</code></em>: <code class="literal">long</code> (tapset
extracts and returns an integer) and <code class="literal">string</code> (tapset
extracts and returns a string).
</p><p>
In some cases, tapsets do not have a <em class="replaceable"><code>return</code></em>
value. This simply means that the tapset does not extract anything from
the kernel. This is common among asynchronous events such as timers,
exit functions, and print functions.
</p></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="index.html">Prev</a> </td><td width="20%" align="center"> </td><td width="40%" align="right"> <a accesskey="n" href="ch02.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">SystemTap Tapset Reference Manual </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 2. Context Functions</td></tr></table></div></body></html>
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