SIGHOLD(P) POSIX Programmer's Manual SIGHOLD(P)NAME
sighold, sigignore, sigpause, sigrelse, sigset - signal management
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);
DESCRIPTION
Use of any of these functions is unspecified in a multi-threaded
process.
The sighold(), sigignore(), sigpause(), sigrelse(), and sigset() func‐
tions provide simplified signal management.
The sigset() function shall modify signal dispositions. The sig argu‐
ment 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 sys‐
tem shall add sig to the calling process' signal mask before executing
the signal handler; when the signal handler returns, the system shall
restore the calling process' signal mask 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 calling process' signal
mask 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 call‐
ing process' signal mask.
The sighold() function shall add sig to the calling process' signal
mask.
The sigrelse() function shall remove sig from the calling process' sig‐
nal mask.
The sigignore() function shall set the disposition of sig to SIG_IGN.
The sigpause() function shall remove sig from the calling process' sig‐
nal mask and suspend the calling process until a signal is received.
The sigpause() function shall restore the process' signal mask 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 trans‐
formed into zombie processes, it shall block until all of its children
terminate, and wait(), waitid(), and waitpid() shall fail and set errno
to [ECHILD].
RETURN VALUE
Upon successful completion, sigset() shall return SIG_HOLD if the sig‐
nal 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.
ERRORS
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.
EXAMPLES
None.
APPLICATION USAGE
The sigaction() function provides a more comprehensive and reliable
mechanism for controlling signals; new applications should use sigac‐
tion() rather than sigset().
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.
The sigsuspend() function should be used in preference to sigpause()
for broader portability.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
Signal Concepts , exec() , pause() , sigaction() , signal() , sigsus‐
pend() , waitid() , the Base Definitions volume of
IEEE Std 1003.1-2001, <signal.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 SIGHOLD(P)
