This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

       None.

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
       for Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group  Base
       Specifications  Issue  7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics
       Engineers, Inc and The Open Group.  In the event of any discrepancy between this version and the original
       IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee  document.
       The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

       Any  typographical  or formatting errors that appear in this page are most likely to have been introduced
       during  the  conversion  of  the  source  files  to  man  page  format.  To  report  such   errors,   see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                                   2017                                     SIGADDSET(3POSIX)

       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.

       The sigaddset() function may fail if:

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

       Thefollowingsectionsareinformative.

       None.

       None.

       sigaddset — add a signal to a signal set

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of this interface
       may differ (consult the corresponding Linux manual page for details of Linux behavior), or the  interface
       may not be implemented on Linux.

       None.

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

Section2.4,  SignalConcepts, pthread_sigmask(), sigaction(), sigdelset(), sigemptyset(), sigfillset(),
       sigismember(), sigpending(), sigsuspend()

       The Base Definitions volume of POSIX.1‐2017, <signal.h>

       #include <signal.h>

       int sigaddset(sigset_t *set, int signo);