This section describes how to write a signal handler function that can
be established with the
A signal handler is just a function that you compile together with the
rest of the program. Instead of directly invoking the function, you use
sigaction to tell the operating system to call
it when a signal arrives. This is known as establishing the
handler. See Signal Actions.
There are two basic strategies you can use in signal handler functions:
You need to take special care in writing handler functions because they can be called asynchronously. That is, a handler might be called at any point in the program, unpredictably. If two signals arrive during a very short interval, one handler can run within another. This section describes what your handler should do, and what you should avoid.
|• Handler Returns||Handlers that return normally, and what this means.|
|• Termination in Handler||How handler functions terminate a program.|
|• Longjmp in Handler||Nonlocal transfer of control out of a signal handler.|
|• Signals in Handler||What happens when signals arrive while the handler is already occupied.|
|• Merged Signals||When a second signal arrives before the first is handled.|
|• Nonreentrancy||Do not call any functions unless you know they are reentrant with respect to signals.|
|• Atomic Data Access||A single handler can run in the middle of reading or writing a single object.|