NAME

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

LIBRARY

       Standard C library (libc, -lc)

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 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(), sigaddset(), sigdelset(),         │ Thread safety │ MT-Safe │
       │sigismember(), sigisemptyset(), sigorset(), sigandset()        │               │         │
       └───────────────────────────────────────────────────────────────┴───────────────┴─────────┘

VERSIONS

   GNU
       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.

STANDARDS

       POSIX.1-2008.

HISTORY

       POSIX.1-2001.

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.

SEE ALSO

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