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<!DOCTYPE concept
  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
<concept id="GUID-6CF8A41B-C2DD-5D57-A71D-6405CE08A06B" xml:lang="en"><title>Using
Signals to Handle Asynchronous Events</title><prolog><metadata><keywords/></metadata></prolog><conbody>
<p>You can use signals to handle asynchronous user events. A process (program
code) can send a signal to itself that can be handled asynchronously based
on the signal handler registered for it. This provides a way to perform tasks
in parallel without any complex thread manipulation in the program code. </p>
<p>The following example code demonstrates how a program code sets a signal
to itself and how it handles the signal asynchronously in a signal handler: </p>
<codeblock id="GUID-4424321B-112A-5556-AD29-41F613A60C84" xml:space="preserve">#include &lt;signal.h&gt;
#include &lt;stdio.h&gt;
void sighandler(int signum)
    {
    if(signum == SIGUSR1)
        {
        // Code to perform custom handling
        }
    else if(signum == SIGUSR2)
        {
        // Code to perform custom handling
        }
    }
int main()
    {
    signal(SIGUSR1,sighandler);
    signal(SIGUSR2,sighandler);
    // program logic
    raise(SIGUSR1); // indicates user event one
    // program logic
    raise(SIGUSR2); // indicates user event two
    // program logic
    return 0;
    }</codeblock>
</conbody><related-links>
<link href="GUID-66C1493D-5B85-558A-9A39-454E6EBA307B.dita"><linktext>Signal Emulation
on the Symbian Platform</linktext></link>
<link href="GUID-186B9876-2A08-5F23-BB49-49EC34C51507.dita"><linktext>Using Signals
to Terminate Processes</linktext></link>
<link href="GUID-E65D91AE-482F-5592-B83C-0F29126C2EFA.dita"><linktext>Using Signals
to Handle Exceptions</linktext></link>
</related-links></concept>