sigpending(2)

NAME
sigpending, rt_sigpending - examine pending signals

LIBRARY
Standard C library (libc, -lc)

SYNOPSIS
#include <signal.h>

int sigpending(sigset_t *set);

    Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

sigpending():
    _POSIX_C_SOURCE

DESCRIPTION
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 set.

RETURN VALUE
sigpending() returns 0 on success. On failure, -1 is returned and errno is set to indicate the error.

ERRORS

EFAULT
    set points to memory which is not a valid part of the process address space.

STANDARDS
POSIX.1-2024.

HISTORY
POSIX.1-2001.

  C library/kernel differences
The original Linux system call was named sigpending(). However, with the addition of real-time signals in Linux 2.2, the fixed-size, 32-bit sigset_t argument supported by that system call was no longer fit for purpose. Consequently, a new system call, rt_sigpending(), was added to support an enlarged sigset_t type. The new system call takes a second argument, size_t sigsetsize, which specifies the size in bytes of the signal set in set. The glibc sigpending() wrapper function hides these details from us, transparently calling rt_sigpending() when the kernel provides it.

NOTES
See sigsetops(3) for details on manipulating signal sets.

If a signal is both blocked and has a disposition of "ignored", it is not added to the mask of pending signals when generated.

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 signal(7).

A child created via fork(2) initially has an empty pending signal set; the pending signal set is preserved across an execve(2).

BUGS
Up to and including glibc 2.2.1, there is a bug in the wrapper function for sigpending() which means that information about pending real-time signals is not correctly returned.

SEE ALSO
kill(2), sigaction(2), signal(2), sigprocmask(2), sigsuspend(2), sigsetops(3), signal(7)