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Next: <a href="Target-Commands.html#Target-Commands" accesskey="n" rel="next">Target Commands</a>, Up: <a href="Targets.html#Targets" accesskey="u" rel="up">Targets</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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<a name="Active-Targets-1"></a>
<h3 class="section">19.1 Active Targets</h3>

<a name="index-stacking-targets"></a>
<a name="index-active-targets"></a>
<a name="index-multiple-targets"></a>

<p>There are multiple classes of targets such as: processes, executable files or
recording sessions.  Core files belong to the process class, making core file
and process mutually exclusive.  Otherwise, <small>GDB</small> can work concurrently
on multiple active targets, one in each class.  This allows you to (for
example) start a process and inspect its activity, while still having access to
the executable file after the process finishes.  Or if you start process
recording (see <a href="Reverse-Execution.html#Reverse-Execution">Reverse Execution</a>) and <code>reverse-step</code> there, you are
presented a virtual layer of the recording target, while the process target
remains stopped at the chronologically last point of the process execution.
</p>
<p>Use the <code>core-file</code> and <code>exec-file</code> commands to select a new core
file or executable target (see <a href="Files.html#Files">Commands to Specify Files</a>).  To
specify as a target a process that is already running, use the <code>attach</code>
command (see <a href="Attach.html#Attach">Debugging an Already-running Process</a>).
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