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(libc.info)Defining Handlers

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Defining Signal Handlers
========================

   This section describes how to write a signal handler function that
can be established with the `signal' or `sigaction' functions.

   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 `signal' or `sigaction' to tell the operating system to call it
when a signal arrives.  This is known as "establishing" the handler.
Note: Signal Actions.

   There are two basic strategies you can use in signal handler
functions:

   * You can have the handler function note that the signal arrived by
     tweaking some global data structures, and then return normally.

   * You can have the handler function terminate the program or transfer
     control to a point where it can recover from the situation that
     caused the signal.

   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.