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.\" Modified by aeb, 960721
.\" 2005-11-21, mtk, added descriptions of sigisemptyset(), sigandset(),
.\"                  and sigorset()
.\" 2007-10-26 mdw   added wording that a sigset_t must be initialized
.\"                  prior to use
.\"
.TH SIGSETOPS 3 2020-12-21 "Linux" "Linux Programmer's Manual"
.SH NAME
sigemptyset, sigfillset, sigaddset, sigdelset, sigismember \- POSIX
signal set operations
.SH SYNOPSIS
.B #include <signal.h>
.PP
.BI "int sigemptyset(sigset_t *" set );
.PP
.BI "int sigfillset(sigset_t *" set );
.PP
.BI "int sigaddset(sigset_t *" set ", int " signum );
.PP
.BI "int sigdelset(sigset_t *" set ", int " signum );
.PP
.BI "int sigismember(const sigset_t *" set ", int " signum );
.PP
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.PP
.ad l
.BR sigemptyset (),
.BR sigfillset (),
.BR sigaddset (),
.BR sigdelset (),
.BR sigismember ():
.RS 4
_POSIX_C_SOURCE
.RE
.ad b
.SH DESCRIPTION
These functions allow the manipulation of POSIX signal sets.
.PP
.BR sigemptyset ()
initializes the signal set given by
.I set
to empty, with all signals excluded from the set.
.PP
.BR sigfillset ()
initializes
.I set
to full, including all signals.
.PP
.BR sigaddset ()
and
.BR sigdelset ()
add and delete respectively signal
.I signum
from
.IR set .
.PP
.BR sigismember ()
tests whether
.I signum
is a member of
.IR set .
.PP
Objects of type
.I sigset_t
must be initialized by a call to either
.BR sigemptyset ()
or
.BR sigfillset ()
before being passed to the functions
.BR sigaddset (),
.BR sigdelset (),
and
.BR sigismember ()
or the additional glibc functions described below
.RB ( sigisemptyset (),
.BR sigandset (),
and
.BR sigorset ()).
The results are undefined if this is not done.
.SH RETURN VALUE
.BR sigemptyset (),
.BR sigfillset (),
.BR sigaddset (),
and
.BR sigdelset ()
return 0 on success and \-1 on error.
.PP
.BR sigismember ()
returns 1 if
.I signum
is a member of
.IR set ,
0 if
.I signum
is not a member, and \-1 on error.
.PP
On error, these functions set
.I errno
to indicate the cause of the error.
.SH ERRORS
.TP
.B EINVAL
.I signum
is not a valid signal.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lbw31 lb lb
l l l.
Interface	Attribute	Value
T{
.BR sigemptyset (),
.BR sigfillset (),
.br
.BR sigaddset (),
.BR sigdelset (),
.br
.BR sigismember (),
.BR sigisemptyset (),
.br
.BR sigorset (),
.BR sigandset ()
T}	Thread safety	MT-Safe
.TE
.SH CONFORMING TO
POSIX.1-2001, POSIX.1-2008.
.SH NOTES
When creating a filled signal set, the glibc
.BR sigfillset ()
function does not include the two real-time signals used internally
by the NPTL threading implementation.
See
.BR nptl (7)
for details.
.\"
.SS Glibc extensions
If the
.B _GNU_SOURCE
feature test macro is defined, then \fI<signal.h>\fP
exposes three other functions for manipulating signal
sets:
.PP
.nf
.BI "int sigisemptyset(const sigset_t *" set );
.BI "int sigorset(sigset_t *" dest ", const sigset_t *" left ,
.BI "              const sigset_t *" right );
.BI "int sigandset(sigset_t *" dest ", const sigset_t *" left ,
.BI "              const sigset_t *" right );
.fi
.PP
.BR sigisemptyset ()
returns 1 if
.I set
contains no signals, and 0 otherwise.
.PP
.BR sigorset ()
places the union of the sets
.I left
and
.I right
in
.IR dest .
.BR sigandset ()
places the intersection of the sets
.I left
and
.I right
in
.IR dest .
Both functions return 0 on success, and \-1 on failure.
.PP
These functions are nonstandard (a few other systems provide similar
functions) and their use should be avoided in portable applications.
.SH SEE ALSO
.BR sigaction (2),
.BR sigpending (2),
.BR sigprocmask (2),
.BR sigsuspend (2)
.SH COLOPHON
This page is part of release 5.10 of the Linux
.I man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
\%https://www.kernel.org/doc/man\-pages/.