sigwait(3)sigwait(3)NAME
sigwait, sigwaitinfo, sigtimedwait - Suspend a calling thread until a
signal arrives
SYNOPSIS
#include <signal.h>
int sigwait(
const sigset_t *set,
int *signal ); int sigwaitinfo(
const sigset_t *set,
siginfo_t *info ); int sigtimedwait(
const sigset_t *set,
siginfo_t *info,
const struct timespec *timeout );
LIBRARY
Threads Library (libpthread.so): sigwait()
Realtime Library (librt.a, librt.so): sigwaitinfo(), sigtimedwait()PARAMETERS
Specifies the set of signals to wait for. Returns the signal number of
the selected signal. (See the DESCRIPTION section for information about
the selected signal.) Specifies a pointer to a siginfo structure that
is receiving data describing the signal, including any application-
defined data specified when the signal was posted. Specifies a timeout
for the wait. If timeout is null, the argument is ignored.
DESCRIPTION
The sigwait functions suspend the calling thread until at least one of
the signals in the set parameter is in the caller's set of pending sig‐
nals. When this happens, one of those signals is automatically selected
and removed from the set of pending signals. The signal number identi‐
fying that signal is then returned.
For the sigwait() function, the signal number is stored in the signal
argument. For the sigwaitinfo() and sigtimedwait() functions, if the
info argument is specified, the selected signal number is stored in the
si_signo member of siginfo structure, and the cause of the signal is
stored in the si_code member. If any value is queued to the selected
signal, the first queued value is dequeued and stored in the si_value
member of info. If no value is queued, the content of the si_value mem‐
ber is undefined.
For sigtimedwait(), if the timeout parameter is specified, the function
waits for the specified time interval. If the timespec structure spec‐
ified contains a timeout value of zero (0), and if none of the signals
specified by set are pending, then sigtimedwait() returns immediately
with an error.
The effect is unspecified if any signals in the set parameter are not
blocked when the sigwait functions are called.
The set parameter is created using the set manipulation functions
sigemptyset(), sigfillset(), sigaddset(), and sigdelset().
If, while the sigwait functions are waiting, a signal occurs that is
eligible for delivery (that is, not blocked by the signal mask), that
signal is handled asynchronously and the wait is interrupted.
RETURN VALUES
Upon successful completion, the sigwait() function returns 0 (zero).
The other functions return the number of the selected signal.
On failure, sigwait() returns the errno value for the failure. The
other functions return -1 and set errno to indicate the error.
ERRORS
If the sigwait functions fail, errno is set to one of the following
values: The value of the set parameter contains an invalid or unsup‐
ported signal number. The timeout argument specified a tv_nsec value
that is less than 0 or greater than or equal to 1,000,000,000. The
wait was interrupted by an unblocked, caught signal. No signal speci‐
fied by set was delivered within the specified timeout period.
SEE ALSO
Headers: siginfo(5)
Functions: sigaction(2), sigpending(2), sigsuspend(2)
Routines: sigaddset(3), sigdelset(3), sigemptyset(3), sigfillset(3)sigwait(3)
