NAME

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

SYNOPSIS

       #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 feature_test_macros(7)):

       sigemptyset(), sigfillset(), sigaddset(), sigdelset(), sigismember():
           _POSIX_C_SOURCE

DESCRIPTION

       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 signal 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.

RETURN VALUE

       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.

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

ERRORS

       EINVAL signum is not a valid signal.

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).

       ┌────────────────────────────────┬───────────────┬─────────┐
       │Interface                       │ Attribute     │ Value   │
       ├────────────────────────────────┼───────────────┼─────────┤
       │sigemptyset(), sigfillset(),    │ Thread safety │ MT-Safe │
       │sigaddset(), sigdelset(),       │               │         │
       │sigismember(), sigisemptyset(), │               │         │
       │sigorset(), sigandset()         │               │         │
       └────────────────────────────────┴───────────────┴─────────┘

CONFORMING TO

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

NOTES

       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 otherwise.

       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 portable applications.

SEE ALSO

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

COLOPHON

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