The Open Group Base Specifications Issue 6
IEEE Std 1003.1, 2004 Edition
Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.

#### NAME

> sigaddset - add a signal to a signal set

#### SYNOPSIS

> ``[CX] #include <signal.h>
> int sigaddset(sigset_t *`set`, int` signo`);``
> `
> `

#### DESCRIPTION

> 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.

#### RETURN VALUE

> Upon successful completion, sigaddset() shall return 0; otherwise, it shall return -1 and set errno to indicate the error.

#### ERRORS

> The sigaddset() function may fail if:

> [EINVAL]
>   The value of the signo argument is an invalid or unsupported signal number.

The following sections are informative.

#### EXAMPLES

> None.

#### APPLICATION USAGE

> None.

#### RATIONALE

> None.

#### FUTURE DIRECTIONS

> None.

#### SEE ALSO

> Signal Concepts, sigaction(), sigdelset(), sigemptyset(), sigfillset(), sigismember(), sigpending(), sigprocmask(), sigsuspend(), the Base Definitions volume of IEEE Std 1003.1-2001, <signal.h>

#### CHANGE HISTORY

> First released in Issue 3. Included for alignment with the POSIX.1-1988 standard.

#### Issue 5

> The last paragraph of the DESCRIPTION was included as an APPLICATION USAGE note in previous issues.

#### Issue 6

> The DESCRIPTION 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.

End of informative text.

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