man2/sigpending.2

   1 .\" Copyright (c) 2005 Michael Kerrisk
   2 .\" based on earlier work by faith@cs.unc.edu and
   3 .\" Mike Battersby <mib@deakin.edu.au>
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  27 .\" 2005-09-15, mtk, Created new page by splitting off from sigaction.2
  28 .\"
  29 .TH SIGPENDING 2 2017-09-15 "Linux" "Linux Programmer's Manual"
  30 .SH NAME
  31 sigpending, rt_sigpending \- examine pending signals
  32 .SH SYNOPSIS
  33 .B #include <signal.h>
  34 .PP
  35 .BI "int sigpending(sigset_t *" set );
  36 .PP
  37 .in -4n
  38 Feature Test Macro Requirements for glibc (see
  39 .BR feature_test_macros (7)):
  40 .in
  41 .PP
  42 .ad l
  43 .BR sigpending ():
  44 _POSIX_C_SOURCE
  45 .ad b
  46 .SH DESCRIPTION
  47 .PP
  48 .BR sigpending ()
  49 returns the set of signals that are pending for delivery to the calling
  50 thread (i.e., the signals which have been raised while blocked).
  51 The mask of pending signals is returned in
  52 .IR set .
  53 .SH RETURN VALUE
  54 .BR sigpending ()
  55 returns 0 on success and \-1 on error.
  56 In the event of an error,
  57 .I errno
  58 is set to indicate the cause.
  59 .SH ERRORS
  60 .TP
  61 .B EFAULT
  62 .I set
  63 points to memory which is not a valid part of the process address space.
  64 .SH CONFORMING TO
  65 POSIX.1-2001, POSIX.1-2008.
  66 .SH NOTES
  67 See
  68 .BR sigsetops (3)
  69 for details on manipulating signal sets.
  70 .PP
  71 If a signal is both blocked and has a disposition of "ignored", it is
  72 .I not
  73 added to the mask of pending signals when generated.
  74 .PP
  75 The set of signals that is pending for a thread
  76 is the union of the set of signals that is pending for that thread
  77 and the set of signals that is pending for the process as a whole; see
  78 .BR signal (7).
  79 .PP
  80 A child created via
  81 .BR fork (2)
  82 initially has an empty pending signal set;
  83 the pending signal set is preserved across an
  84 .BR execve (2).
  85 .\"
  86 .SS C library/kernel differences
  87 The original Linux system call was named
  88 .BR sigpending ().
  89 However, with the addition of real-time signals in Linux 2.2,
  90 the fixed-size, 32-bit
  91 .IR sigset_t
  92 argument supported by that system call was no longer fit for purpose.
  93 Consequently, a new system call,
  94 .BR rt_sigpending (),
  95 was added to support an enlarged
  96 .IR sigset_t
  97 type.
  98 The new system call takes a second argument,
  99 .IR "size_t sigsetsize" ,
 100 which specifies the size in bytes of the signal set in
 101 .IR set .
 102 .\" This argument is currently required to be less than or equal to
 103 .\" .IR sizeof(sigset_t)
 104 .\" (or the error
 105 .\" .B EINVAL
 106 .\" results).
 107 The glibc
 108 .BR sigpending ()
 109 wrapper function hides these details from us, transparently calling
 110 .BR rt_sigpending ()
 111 when the kernel provides it.
 112 .\"
 113 .SH BUGS
 114 In versions of glibc up to and including 2.2.1,
 115 there is a bug in the wrapper function for
 116 .BR sigpending ()
 117 which means that information about pending real-time signals
 118 is not correctly returned.
 119 .SH SEE ALSO
 120 .BR kill (2),
 121 .BR sigaction (2),
 122 .BR signal (2),
 123 .BR sigprocmask (2),
 124 .BR sigsuspend (2),
 125 .BR sigsetops (3),
 126 .BR signal (7)