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          sigemptyset, sigfillset, sigaddset, sigdelset, sigismember -
          POSIX signal set operations

          #include <signal.h>

          int sigemptyset(sigset_t *set);

          int sigfillset(sigset_t *set);

          int sigaddset(sigset_t *set, int signum);

          int sigdelset(sigset_t *set, int signum);

          int sigismember(const sigset_t *set, int signum);

     Feature Test Macro Requirements for glibc (see

          sigemptyset(), sigfillset(), sigaddset(), sigdelset(),

          These functions allow the manipulation of POSIX signal sets.

          sigemptyset() initializes the signal set  given  by  set  to
          empty, with all signals excluded from the set.

          sigfillset() initializes set to full, including all signals.

          sigaddset() and sigdelset() add and delete respectively sig-
          nal signum from set.

          sigismember() tests whether signum is a member of set.

          Objects of type sigset_t must be initialized by  a  call  to
          either  sigemptyset() or sigfillset() before being passed to
          the functions sigaddset(), sigdelset(), and sigismember() or
          the    additional    glibc    functions    described   below
          (sigisemptyset(), sigandset(), and sigorset()).  The results
          are undefined if this is not done.

          sigemptyset(), sigfillset(),  sigaddset(),  and  sigdelset()
          return 0 on success and -1 on error.

          sigismember() returns 1 if signum is a member of set,  0  if
          signum is not a member, and -1 on error.

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          On error, these functions set errno to indicate the cause of
          the error.

               signum is not a valid signal.

          For an explanation of the terms used in  this  section,  see
          attributes(7).     allbox;    lbw31    lb    lb   l   l   l.
          Interface Attribute Value T{ sigemptyset(), sigfillset(),
          sigaddset(), sigdelset(),
          sigismember(), sigisemptyset(),
          sigorset(), sigandset() T}   Thread safety  MT-Safe

          POSIX.1-2001, POSIX.1-2008.

          When creating a filled signal set,  the  glibc  sigfillset()
          function  does  not  include  the two real-time signals used
          internally  by  the  NPTL  threading  implementation.    See
          nptl(7) for details.

        Glibc extensions
          If the _GNU_SOURCE  feature  test  macro  is  defined,  then
          <signal.h>  exposes  three  other functions for manipulating
          signal sets:

          int sigisemptyset(const sigset_t *set);
          int sigorset(sigset_t *dest, const sigset_t *left,
                        const sigset_t *right);
          int sigandset(sigset_t *dest, const sigset_t *left,
                        const sigset_t *right);

          sigisemptyset() returns 1 if set contains no signals, and  0

          sigorset() places the union of the sets left  and  right  in
          dest.  sigandset()  places the intersection of the sets left
          and right in dest. Both functions return 0 on  success,  and
          -1 on failure.

          These functions are nonstandard (a few other systems provide
          similar  functions) and their use should be avoided in port-
          able applications.

          sigaction(2), sigpending(2), sigprocmask(2), sigsuspend(2)

          This page is part of release 5.10  of  the  Linux  man-pages

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          project.   A  description  of the project, information about
          reporting bugs, and the latest version of this page, can  be
          found at

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