mirror of
https://github.com/autc04/Retro68.git
synced 2024-11-28 05:51:04 +00:00
75 lines
2.3 KiB
TeX
75 lines
2.3 KiB
TeX
@node Signals
|
|
@chapter Signal Handling (@file{signal.h})
|
|
|
|
A @dfn{signal} is an event that interrupts the normal flow of control
|
|
in your program. Your operating environment normally defines the full
|
|
set of signals available (see @file{sys/signal.h}), as well as the
|
|
default means of dealing with them---typically, either printing an
|
|
error message and aborting your program, or ignoring the signal.
|
|
|
|
All systems support at least the following signals:
|
|
@table @code
|
|
@item SIGABRT
|
|
Abnormal termination of a program; raised by the @code{abort} function.
|
|
|
|
@item SIGFPE
|
|
A domain error in arithmetic, such as overflow, or division by zero.
|
|
|
|
@item SIGILL
|
|
Attempt to execute as a function data that is not executable.
|
|
|
|
@item SIGINT
|
|
Interrupt; an interactive attention signal.
|
|
|
|
@item SIGSEGV
|
|
An attempt to access a memory location that is not available.
|
|
|
|
@item SIGTERM
|
|
A request that your program end execution.
|
|
@end table
|
|
|
|
Two functions are available for dealing with asynchronous
|
|
signals---one to allow your program to send signals to itself (this is
|
|
called @dfn{raising} a signal), and one to specify subroutines (called
|
|
@dfn{handlers} to handle particular signals that you anticipate may
|
|
occur---whether raised by your own program or the operating environment.
|
|
|
|
To support these functions, @file{signal.h} defines three macros:
|
|
|
|
@table @code
|
|
@item SIG_DFL
|
|
Used with the @code{signal} function in place of a pointer to a
|
|
handler subroutine, to select the operating environment's default
|
|
handling of a signal.
|
|
|
|
@item SIG_IGN
|
|
Used with the @code{signal} function in place of a pointer to a
|
|
handler, to ignore a particular signal.
|
|
|
|
@item SIG_ERR
|
|
Returned by the @code{signal} function in place of a pointer to a
|
|
handler, to indicate that your request to set up a handler could not
|
|
be honored for some reason.
|
|
@end table
|
|
|
|
@file{signal.h} also defines an integral type, @code{sig_atomic_t}.
|
|
This type is not used in any function declarations; it exists only to
|
|
allow your signal handlers to declare a static storage location where
|
|
they may store a signal value. (Static storage is not otherwise
|
|
reliable from signal handlers.)
|
|
|
|
@menu
|
|
* psignal:: Print a signal message to standard error
|
|
* raise:: Send a signal
|
|
* signal:: Specify handler subroutine for a signal
|
|
@end menu
|
|
|
|
@page
|
|
@include signal/psignal.def
|
|
|
|
@page
|
|
@include signal/raise.def
|
|
|
|
@page
|
|
@include signal/signal.def
|