-.so man2/sigaction.2
+.\" Copyright (c) 2005 Michael Kerrisk
+.\" based on earlier work by faith@cs.unc.edu and
+.\" Mike Battersby <mib@deakin.edu.au>
+.\"
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+.\" entire resulting derived work is distributed under the terms of a
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+.\" manual page may be incorrect or out-of-date. The author(s) assume no
+.\" responsibility for errors or omissions, or for damages resulting from
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+.\"
+.\" 2005-09-15, mtk, Created new page by splitting off from sigaction.2
+.\"
+.TH SIGPENDING 2 2017-09-15 "Linux" "Linux Programmer's Manual"
+.SH NAME
+sigpending, rt_sigpending \- examine pending signals
+.SH SYNOPSIS
+.B #include <signal.h>
+.PP
+.BI "int sigpending(sigset_t *" set );
+.PP
+.in -4n
+Feature Test Macro Requirements for glibc (see
+.BR feature_test_macros (7)):
+.in
+.PP
+.ad l
+.BR sigpending ():
+_POSIX_C_SOURCE
+.ad b
+.SH DESCRIPTION
+.PP
+.BR sigpending ()
+returns the set of signals that are pending for delivery to the calling
+thread (i.e., the signals which have been raised while blocked).
+The mask of pending signals is returned in
+.IR set .
+.SH RETURN VALUE
+.BR sigpending ()
+returns 0 on success and \-1 on error.
+In the event of an error,
+.I errno
+is set to indicate the cause.
+.SH ERRORS
+.TP
+.B EFAULT
+.I set
+points to memory which is not a valid part of the process address space.
+.SH CONFORMING TO
+POSIX.1-2001, POSIX.1-2008.
+.SH NOTES
+See
+.BR sigsetops (3)
+for details on manipulating signal sets.
+.PP
+If a signal is both blocked and has a disposition of "ignored", it is
+.I not
+added to the mask of pending signals when generated.
+.PP
+The set of signals that is pending for a thread
+is the union of the set of signals that is pending for that thread
+and the set of signals that is pending for the process as a whole; see
+.BR signal (7).
+.PP
+A child created via
+.BR fork (2)
+initially has an empty pending signal set;
+the pending signal set is preserved across an
+.BR execve (2).
+.\"
+.SS C library/kernel differences
+The original Linux system call was named
+.BR sigpending ().
+However, with the addition of real-time signals in Linux 2.2,
+the fixed-size, 32-bit
+.IR sigset_t
+argument supported by that system call was no longer fit for purpose.
+Consequently, a new system call,
+.BR rt_sigpending (),
+was added to support an enlarged
+.IR sigset_t
+type.
+The new system call takes a second argument,
+.IR "size_t sigsetsize" ,
+which specifies the size in bytes of the signal set in
+.IR set .
+.\" This argument is currently required to be less than or equal to
+.\" .IR sizeof(sigset_t)
+.\" (or the error
+.\" .B EINVAL
+.\" results).
+The glibc
+.BR sigpending ()
+wrapper function hides these details from us, transparently calling
+.BR rt_sigpending ()
+when the kernel provides it.
+.\"
+.SH BUGS
+In versions of glibc up to and including 2.2.1,
+there is a bug in the wrapper function for
+.BR sigpending ()
+which means that information about pending real-time signals
+is not correctly returned.
+.SH SEE ALSO
+.BR kill (2),
+.BR sigaction (2),
+.BR signal (2),
+.BR sigprocmask (2),
+.BR sigsuspend (2),
+.BR sigsetops (3),
+.BR signal (7)
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