#include <signal.h> int sigsuspend(const sigset_t *set);
The sigsuspend() function replaces the caller's signal mask with the set of signals pointed to by the set argument and suspends the caller until delivery of a signal whose action is either to execute a signal catching function or to terminate the process. If the set argument points to an invalid address, the behavior is undefined and errno may be set to EFAULT.
If the action is to terminate the process, sigsuspend() does not return. If the action is to execute a signal catching function, sigsuspend() returns after the signal catching function returns. On return, the signal mask is restored to the set that existed before the call to sigsuspend().
It is not possible to block signals that cannot be ignored (see signal.h(3HEAD)). This restriction is silently imposed by the system.
Since sigsuspend() suspends the caller's execution indefinitely, there is no successful completion return value. On failure, it returns −1 and sets errno to indicate the error.
The sigsuspend() function will fail if:
A signal was caught by the caller and control was returned from the signal catching function.
The sigsuspend() function may fail if:
The set argument points to an illegal address.
See attributes(5) for descriptions of the following attributes:
If the caller specifies more than one unblocked signal in the mask to sigsuspend(), more than one signal might be processed before the call to sigsuspend() returns.
While the caller is executing the signal handler that interrupted its call to sigsuspend(), its signal mask is the one passed to sigsuspend(), modified as usual by the signal mask specification in the signal's sigaction(2) parameters. The caller's signal mask is not restored to its previous value until the caller returns from all the signal handlers that interrupted sigsuspend().