Section (2) sigpending
sigpending, rt_sigpending — examine pending signals
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
sigpending() returns 0 on
success and −1 on error. In the event of an error,
errno is set to indicate the
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).
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
In versions of glibc up to and including 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
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Copyright (c) 2005 Michael Kerrisk
based on earlier work by faithcs.unc.edu and
Mike Battersby <mibdeakin.edu.au>
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2005-09-15, mtk, Created new page by splitting off from sigaction.2