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HP-UX 11i Version 3: February 2007

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sigsuspend — wait for a signal


#include <signal.h>

int sigsuspend(const sigset_t *sigmask);


The sigsuspend() function replaces the current signal mask of the calling thread with the set of signals pointed to by sigmask and then suspends the thread until delivery of a signal whose action is either to execute a signal-catching function or to terminate the process. This will 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() will never return. If the action is to execute a signal-catching function, then sigsuspend() will return after the signal-catching function returns, with the signal mask restored to the set that existed prior to the sigsuspend() call.

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 is returned and errno is set to indicate the error.


The sigsuspend() function will fail if:


A signal is caught by the calling process and control is returned from the signal-catching function.


sigmask points to an invalid address. The reliable detection of this error is implementation-dependent.


Threads Considerations

Since blocked signal masks are maintained at the thread level, sigsuspend() modifies only the calling thread's blocked signal mask. sigsuspend() suspends only the calling thread until it receives a signal.

If other threads in the process do not block the signal, the signal may be delivered to another thread in the process and the thread in sigsuspend() may continue waiting. For this reason, the use of sigwait(2) is recommended instead of sigsuspend() for multi-threaded applications.

For more information regarding signals and threads, refer to signal(5).

LWP (Lightweight Processes) Considerations

sigsuspend() modifies only the calling LWP's signal mask and suspends only the calling LWP until receipt of a signal.


sigsuspend() was derived from the IEEE POSIX 1003.1-1988 Standard.


First released in Issue 3.

Entry included for alignment with the POSIX.1-1988 standard.


sigsuspend(): AES, SVID3, XPG3, XPG4, FIPS 151-2, POSIX.1

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