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| <!-- %MENU% How to send, block, and handle signals --> |
| <h2 class="chapter">24 Signal Handling</h2> |
| |
| <p><a name="index-signal-2810"></a>A <dfn>signal</dfn> is a software interrupt delivered to a process. The |
| operating system uses signals to report exceptional situations to an |
| executing program. Some signals report errors such as references to |
| invalid memory addresses; others report asynchronous events, such as |
| disconnection of a phone line. |
| |
| <p>The GNU C library defines a variety of signal types, each for a |
| particular kind of event. Some kinds of events make it inadvisable or |
| impossible for the program to proceed as usual, and the corresponding |
| signals normally abort the program. Other kinds of signals that report |
| harmless events are ignored by default. |
| |
| <p>If you anticipate an event that causes signals, you can define a handler |
| function and tell the operating system to run it when that particular |
| type of signal arrives. |
| |
| <p>Finally, one process can send a signal to another process; this allows a |
| parent process to abort a child, or two related processes to communicate |
| and synchronize. |
| |
| <ul class="menu"> |
| <li><a accesskey="1" href="Concepts-of-Signals.html#Concepts-of-Signals">Concepts of Signals</a>: Introduction to the signal facilities. |
| <li><a accesskey="2" href="Standard-Signals.html#Standard-Signals">Standard Signals</a>: Particular kinds of signals with |
| standard names and meanings. |
| <li><a accesskey="3" href="Signal-Actions.html#Signal-Actions">Signal Actions</a>: Specifying what happens when a |
| particular signal is delivered. |
| <li><a accesskey="4" href="Defining-Handlers.html#Defining-Handlers">Defining Handlers</a>: How to write a signal handler function. |
| <li><a accesskey="5" href="Interrupted-Primitives.html#Interrupted-Primitives">Interrupted Primitives</a>: Signal handlers affect use of <code>open</code>, |
| <code>read</code>, <code>write</code> and other functions. |
| <li><a accesskey="6" href="Generating-Signals.html#Generating-Signals">Generating Signals</a>: How to send a signal to a process. |
| <li><a accesskey="7" href="Blocking-Signals.html#Blocking-Signals">Blocking Signals</a>: Making the system hold signals temporarily. |
| <li><a accesskey="8" href="Waiting-for-a-Signal.html#Waiting-for-a-Signal">Waiting for a Signal</a>: Suspending your program until a signal |
| arrives. |
| <li><a accesskey="9" href="Signal-Stack.html#Signal-Stack">Signal Stack</a>: Using a Separate Signal Stack. |
| <li><a href="BSD-Signal-Handling.html#BSD-Signal-Handling">BSD Signal Handling</a>: Additional functions for backward |
| compatibility with BSD. |
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