sigaddset - add a signal to a signal set
The sigaddset() function adds the individual signal specified by the signo to the signal set pointed to by set.
Applications shall call either sigemptyset() or sigfillset() at least once for each object of type sigset_t prior to any other use of that object. If such an object is not initialized in this way, but is nonetheless supplied as an argument to any of pthread_sigmask(), sigaction(), sigaddset(), sigdelset(), sigismember(), sigpending(), sigprocmask(), sigsuspend(), sigtimedwait(), sigwait(), or sigwaitinfo(), the results are undefined.
Upon successful completion, sigaddset() shall return 0; otherwise, it shall return -1 and set errno to indicate the error.
The sigaddset() function may fail if:
- The value of the signo argument is an invalid or unsupported signal number.
Signal Concepts, pthread_sigmask, sigaction, sigdelset, sigemptyset, sigfillset, sigismember, sigpending, sigsuspend
First released in Issue 3. Included for alignment with the POSIX.1-1988 standard.
The last paragraph of the DESCRIPTION was included as an APPLICATION USAGE note in previous issues.
The normative text is updated to avoid use of the term "must" for application requirements.
The SYNOPSIS is marked CX since the presence of this function in the <signal.h> header is an extension over the ISO C standard.
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