SIGSETOPS(3) Library Functions Manual SIGSETOPS(3)
NAME
sigemptyset, sigfillset, sigaddset, sigdelset, sigismember - POSIX sig-
nal 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 sigemp-
tyset() or sigfillset() before being passed to the functions
sigaddset(), sigdelset(), and sigismember() or the additional glibc
functions described below (sigisemptyset(), sigandset(), and sig-
orset()). 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(), │ Thread safety │ MT-Safe │
│ sigdelset(), sigismember(), │ │ │
│ sigisemptyset(), sigorset(), sigandset() │ │ │
└────────────────────────────────────────────┴───────────────┴─────────┘
VERSIONS
GNU
If the _GNU_SOURCE feature test macro is defined, then <signal.h> ex-
poses 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. sigand-
set() 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)
Linux man-pages 6.9.1 2024-05-02 SIGSETOPS(3)
Generated by dwww version 1.16 on Tue Dec 16 04:45:47 CET 2025.