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.
sigsuspend — wait for a signal
int sigsuspend(const sigset_t *sigmask);
The sigsuspend() function shall replace the current signal mask of the
calling thread with the set of signals pointed to by sigmask and then
suspend the thread until delivery of a signal whose action is either to
execute a signal-catching function or to terminate the process. This shall not
cause any other signals that may have been pending on the process to become
pending on the thread.
If the action is to terminate the process then sigsuspend()
shall never return. If the action is to execute a signal-catching function,
then sigsuspend() shall return after the signal-catching function
returns, with the signal mask restored to the set that existed prior to the
It is not possible to block signals that cannot be ignored. This
is enforced by the system without causing an error to be indicated.
Since sigsuspend() suspends thread execution indefinitely, there is no
successful completion return value. If a return occurs, -1 shall be returned
and errno set to indicate the error.
The sigsuspend() function shall fail if:
- A signal is caught by the calling process and control is returned from the
The following sections are informative.
Normally, at the beginning of a critical code section, a specified set of
signals is blocked using the sigprocmask() function. When the thread
has completed the critical section and needs to wait for the previously
blocked signal(s), it pauses by calling sigsuspend() with the mask that
was returned by the sigprocmask() call.
Code which wants to avoid the ambiguity of the signal mask for thread
cancellation handlers can install an additional cancellation handler which
resets the signal mask to the expected value.
Section 2.4, Signal Concepts, pause(),
void cleanup(void *arg)
sigset_t *ss = (sigset_t *) arg;
pthread_sigmask(SIG_SETMASK, ss, NULL);
int call_sigsuspend(const sigset_t *mask)
pthread_sigmask(SIG_SETMASK, NULL, &oldmask);
result = sigsuspend(sigmask);
The Base Definitions volume of POSIX.1‐2017,
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1-2017, Standard for Information Technology -- Portable Operating
System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018
Edition, Copyright (C) 2018 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 .
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