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| <h3 class="section">24.7 Blocking Signals</h3> |
| |
| <p><a name="index-blocking-signals-2956"></a> |
| Blocking a signal means telling the operating system to hold it and |
| deliver it later. Generally, a program does not block signals |
| indefinitely—it might as well ignore them by setting their actions to |
| <code>SIG_IGN</code>. But it is useful to block signals briefly, to prevent |
| them from interrupting sensitive operations. For instance: |
| |
| <ul> |
| <li>You can use the <code>sigprocmask</code> function to block signals while you |
| modify global variables that are also modified by the handlers for these |
| signals. |
| |
| <li>You can set <code>sa_mask</code> in your <code>sigaction</code> call to block |
| certain signals while a particular signal handler runs. This way, the |
| signal handler can run without being interrupted itself by signals. |
| </ul> |
| |
| <ul class="menu"> |
| <li><a accesskey="1" href="Why-Block.html#Why-Block">Why Block</a>: The purpose of blocking signals. |
| <li><a accesskey="2" href="Signal-Sets.html#Signal-Sets">Signal Sets</a>: How to specify which signals to |
| block. |
| <li><a accesskey="3" href="Process-Signal-Mask.html#Process-Signal-Mask">Process Signal Mask</a>: Blocking delivery of signals to your |
| process during normal execution. |
| <li><a accesskey="4" href="Testing-for-Delivery.html#Testing-for-Delivery">Testing for Delivery</a>: Blocking to Test for Delivery of |
| a Signal. |
| <li><a accesskey="5" href="Blocking-for-Handler.html#Blocking-for-Handler">Blocking for Handler</a>: Blocking additional signals while a |
| handler is being run. |
| <li><a accesskey="6" href="Checking-for-Pending-Signals.html#Checking-for-Pending-Signals">Checking for Pending Signals</a>: Checking for Pending Signals |
| <li><a accesskey="7" href="Remembering-a-Signal.html#Remembering-a-Signal">Remembering a Signal</a>: How you can get almost the same |
| effect as blocking a signal, by |
| handling it and setting a flag |
| to be tested later. |
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