управление сигналами (signal management)
Пролог (Prolog)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
Имя (Name)
sighold, sigignore, sigpause, sigrelse, sigset — signal
management
Синопсис (Synopsis)
#include <signal.h>
int sighold(int sig);
int sigignore(int sig);
int sigpause(int sig);
int sigrelse(int sig);
void (*sigset(int sig, void (*disp)(int)))(int);
Описание (Description)
Use of any of these functions is unspecified in a multi-threaded
process.
The sighold(), sigignore(), sigpause(), sigrelse(), and sigset()
functions provide simplified signal management.
The sigset() function shall modify signal dispositions. The sig
argument specifies the signal, which may be any signal except
SIGKILL and SIGSTOP. The disp argument specifies the signal's
disposition, which may be SIG_DFL, SIG_IGN, or the address of a
signal handler. If sigset() is used, and disp is the address of a
signal handler, the system shall add sig to the signal mask of
the calling process before executing the signal handler; when the
signal handler returns, the system shall restore the signal mask
of the calling process to its state prior to the delivery of the
signal. In addition, if sigset() is used, and disp is equal to
SIG_HOLD, sig shall be added to the signal mask of the calling
process and sig's disposition shall remain unchanged. If sigset()
is used, and disp is not equal to SIG_HOLD, sig shall be removed
from the signal mask of the calling process.
The sighold() function shall add sig to the signal mask of the
calling process.
The sigrelse() function shall remove sig from the signal mask of
the calling process.
The sigignore() function shall set the disposition of sig to
SIG_IGN.
The sigpause() function shall remove sig from the signal mask of
the calling process and suspend the calling process until a
signal is received. The sigpause() function shall restore the
signal mask of the process to its original state before
returning.
If the action for the SIGCHLD signal is set to SIG_IGN, child
processes of the calling processes shall not be transformed into
zombie processes when they terminate. If the calling process
subsequently waits for its children, and the process has no
unwaited-for children that were transformed into zombie
processes, it shall block until all of its children terminate,
and wait(), waitid(), and waitpid() shall fail and set errno to
[ECHILD].
Возвращаемое значение (Return value)
Upon successful completion, sigset() shall return SIG_HOLD if the
signal had been blocked and the signal's previous disposition if
it had not been blocked. Otherwise, SIG_ERR shall be returned and
errno set to indicate the error.
The sigpause() function shall suspend execution of the thread
until a signal is received, whereupon it shall return -1 and set
errno to [EINTR].
For all other functions, upon successful completion, 0 shall be
returned. Otherwise, -1 shall be returned and errno set to
indicate the error.
Ошибки (Error)
These functions shall fail if:
EINVAL The sig argument is an illegal signal number.
The sigset() and sigignore() functions shall fail if:
EINVAL An attempt is made to catch a signal that cannot be
caught, or to ignore a signal that cannot be ignored.
The following sections are informative.
Примеры (Examples)
None.
Использование в приложениях (Application usage)
The sigaction() function provides a more comprehensive and
reliable mechanism for controlling signals; new applications
should use the sigaction() function instead of the obsolescent
sigset() function.
The sighold() function, in conjunction with sigrelse() or
sigpause(), may be used to establish critical regions of code
that require the delivery of a signal to be temporarily deferred.
For broader portability, the pthread_sigmask() or sigprocmask()
functions should be used instead of the obsolescent sighold() and
sigrelse() functions.
For broader portability, the sigsuspend() function should be used
instead of the obsolescent sigpause() function.
Обоснование (Rationale)
Each of these historic functions has a direct analog in the other
functions which are required to be per-thread and thread-safe
(aside from sigprocmask(), which is replaced by
pthread_sigmask()). The sigset() function can be implemented as
a simple wrapper for sigaction(). The sighold() function is
equivalent to sigprocmask() or pthread_sigmask() with SIG_BLOCK
set. The sigignore() function is equivalent to sigaction() with
SIG_IGN set. The sigpause() function is equivalent to
sigsuspend(). The sigrelse() function is equivalent to
sigprocmask() or pthread_sigmask() with SIG_UNBLOCK set.
Будущие направления (Future directions)
These functions may be removed in a future version.
Смотри также (See also)
Section 2.4, Signal Concepts, exec(1p), pause(3p),
pthread_sigmask(3p), sigaction(3p), signal(3p), sigsuspend(3p),
wait(3p), waitid(3p)
The Base Definitions volume of POSIX.1‐2017, signal.h(0p)
