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    <a href="../index-2.html">cppreference.com</a> &gt; <a href=
    "index.html">Other Standard C Functions</a> &gt; <a href=
    "signal.html">signal</a>
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  <div class="name-format">
    signal
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;csignal&gt;
  void ( *signal( int signal, void (* func) (int)) ) (int);
</pre>

  <p>The signal() function sets <em>func</em> to be called when
  <em>signal</em> is recieved by your program. <em>func</em> can be a
  custom signal handler, or one of these macros (defined in
  the csignal header file):</p>

  <table class="code-table">
    <tr>
      <th class="code-table-th">Macro</th>

      <th class="code-table-th">Explanation</th>
    </tr>

    <tr>
      <td class="code-table-td">SIG_DFL</td>

      <td class="code-table-td">default signal handling</td>
    </tr>

    <tr>
      <td class="code-table-td">SIG_IGN</td>

      <td class="code-table-td">ignore the signal</td>
    </tr>
  </table>

  <p>Some basic signals that you can attach a signal handler to
  are:</p>

  <table class="code-table">
    <tr>
      <th class="code-table-th">Signal</th>

      <th class="code-table-th">Description</th>
    </tr>

    <tr>
      <td class="code-table-td">SIGTERM</td>

      <td class="code-table-td">Generic stop signal that can be
      caught.</td>
    </tr>

    <tr>
      <td class="code-table-td">SIGINT</td>

      <td class="code-table-td">Interrupt program, normally
      ctrl-c.</td>
    </tr>

    <tr>
      <td class="code-table-td">SIGQUIT</td>

      <td class="code-table-td">Interrupt program, similar to
      SIGINT.</td>
    </tr>

    <tr>
      <td class="code-table-td">SIGKILL</td>

      <td class="code-table-td">Stops the program. Cannot be
      caught.</td>
    </tr>

    <tr>
      <td class="code-table-td">SIGHUP</td>

      <td class="code-table-td">Reports a disconnected terminal.</td>
    </tr>
  </table>

  <p>The return value of signal() is the address of the previously
  defined function for this signal, or SIG_ERR is there is an
  error.</p>

  <div class="related-examples-format">
    Example code:
  </div>

  <div class="related-examples">
    <p>The following example uses the signal() function to call an
    arbitrary number of functions when the user aborts the program. The
    functions are stored in a vector, and a single &quot;clean-up&quot;
    function calls each function in that vector of functions when the
    program is aborted:</p>
<pre class="prettyprint">
void f1() {
  cout &lt;&lt; &quot;calling f1()...&quot; &lt;&lt; endl;
}

void f2() {
  cout &lt;&lt; &quot;calling f2()...&quot; &lt;&lt; endl;
}

typedef void(*endFunc)(void);
vector&lt;endFunc&gt; endFuncs;

void cleanUp( int dummy ) {
  for( unsigned int i = 0; i &lt; endFuncs.size(); i++ ) {
    endFunc f = endFuncs.at(i);
    (*f)();
  }
  exit(-1);
}

int main() {

  // connect various signals to our clean-up function
  signal( SIGTERM, cleanUp );
  signal( SIGINT, cleanUp );
  signal( SIGQUIT, cleanUp );
  signal( SIGHUP, cleanUp );

  // add two specific clean-up functions to a list of functions
  endFuncs.push_back( f1 );
  endFuncs.push_back( f2 );

  // loop until the user breaks
  while( 1 );

  return 0;
}
</pre>
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    Related topics:
  </div>

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    <a href="raise.html">raise</a>
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