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<h4 class="subsection">24.6.1 Signaling Yourself</h4>

<p>A process can send itself a signal with the <code>raise</code> function.  This
function is declared in <samp><span class="file">signal.h</span></samp>. 
<a name="index-signal_002eh-2948"></a>
<!-- signal.h -->
<!-- ISO -->

<div class="defun">
&mdash; Function: int <b>raise</b> (<var>int signum</var>)<var><a name="index-raise-2949"></a></var><br>
<blockquote><p>The <code>raise</code> function sends the signal <var>signum</var> to the calling
process.  It returns zero if successful and a nonzero value if it fails. 
About the only reason for failure would be if the value of <var>signum</var>
is invalid. 
</p></blockquote></div>

<!-- signal.h -->
<!-- SVID -->
<div class="defun">
&mdash; Function: int <b>gsignal</b> (<var>int signum</var>)<var><a name="index-gsignal-2950"></a></var><br>
<blockquote><p>The <code>gsignal</code> function does the same thing as <code>raise</code>; it is
provided only for compatibility with SVID. 
</p></blockquote></div>

   <p>One convenient use for <code>raise</code> is to reproduce the default behavior
of a signal that you have trapped.  For instance, suppose a user of your
program types the SUSP character (usually <kbd>C-z</kbd>; see <a href="Special-Characters.html#Special-Characters">Special Characters</a>) to send it an interactive stop signal
(<code>SIGTSTP</code>), and you want to clean up some internal data buffers
before stopping.  You might set this up like this:

<!-- RMS suggested getting rid of the handler for SIGCONT in this function. -->
<!-- But that would require that the handler for SIGTSTP unblock the -->
<!-- signal before doing the call to raise.  We haven't covered that -->
<!-- topic yet, and I don't want to distract from the main point of -->
<!-- the example with a digression to explain what is going on.  As -->
<!-- the example is written, the signal that is raise'd will be delivered -->
<!-- as soon as the SIGTSTP handler returns, which is fine. -->
<pre class="smallexample">     #include &lt;signal.h&gt;
     
     /* <span class="roman">When a stop signal arrives, set the action back to the default
        and then resend the signal after doing cleanup actions.</span> */
     
     void
     tstp_handler (int sig)
     {
       signal (SIGTSTP, SIG_DFL);
       /* <span class="roman">Do cleanup actions here.</span> */
       ...
       raise (SIGTSTP);
     }
     
     /* <span class="roman">When the process is continued again, restore the signal handler.</span> */
     
     void
     cont_handler (int sig)
     {
       signal (SIGCONT, cont_handler);
       signal (SIGTSTP, tstp_handler);
     }
     
     /* <span class="roman">Enable both handlers during program initialization.</span> */
     
     int
     main (void)
     {
       signal (SIGCONT, cont_handler);
       signal (SIGTSTP, tstp_handler);
       ...
     }
</pre>
   <p><strong>Portability note:</strong> <code>raise</code> was invented by the ISO&nbsp;C<!-- /@w -->
committee.  Older systems may not support it, so using <code>kill</code> may
be more portable.  See <a href="Signaling-Another-Process.html#Signaling-Another-Process">Signaling Another Process</a>.

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