man2/sigprocmask.2

   1 .\" Copyright (c) 2005 Michael Kerrisk
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   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 SIGPROCMASK 2 2012-04-15 "Linux" "Linux Programmer's Manual"
  30 .SH NAME
  31 sigprocmask \- examine and change blocked signals
  32 .SH SYNOPSIS
  33 .B #include <signal.h>
  34 .sp
  35 .BI "int sigprocmask(int " how ", const sigset_t *" set ,
  36 .BI "sigset_t *" oldset );
  37 .sp
  38 .in -4n
  39 Feature Test Macro Requirements for glibc (see
  40 .BR feature_test_macros (7)):
  41 .in
  42 .sp
  43 .ad l
  44 .BR sigprocmask ():
  45 _POSIX_C_SOURCE\ >=\ 1 || _XOPEN_SOURCE || _POSIX_SOURCE
  46 .ad b
  47 .SH DESCRIPTION
  48 .BR sigprocmask ()
  49 is used to fetch and/or change the signal mask of the calling thread.
  50 The signal mask is the set of signals whose delivery is currently
  51 blocked for the caller
  52 (see also
  53 .BR signal (7)
  54 for more details).
  55
  56 The behavior of the call is dependent on the value of
  57 .IR how ,
  58 as follows.
  59 .TP
  60 .B SIG_BLOCK
  61 The set of blocked signals is the union of the current set and the
  62 .I set
  63 argument.
  64 .TP
  65 .B SIG_UNBLOCK
  66 The signals in
  67 .I set
  68 are removed from the current set of blocked signals.
  69 It is permissible to attempt to unblock a signal which is not blocked.
  70 .TP
  71 .B SIG_SETMASK
  72 The set of blocked signals is set to the argument
  73 .IR set .
  74 .PP
  75 If
  76 .I oldset
  77 is non-NULL, the previous value of the signal mask is stored in
  78 .IR oldset .
  79
  80 If
  81 .I set
  82 is NULL, then the signal mask is unchanged (i.e.,
  83 .I how
  84 is ignored),
  85 but the current value of the signal mask is nevertheless returned in
  86 .I oldset
  87 (if it is not NULL).
  88
  89 The use of
  90 .BR sigprocmask ()
  91 is unspecified in a multithreaded process; see
  92 .BR pthread_sigmask (3).
  93 .SH RETURN VALUE
  94 .BR sigprocmask ()
  95 returns 0 on success and \-1 on error.
  96 .SH ERRORS
  97 .TP
  98 .B EFAULT
  99 the
 100 .I set
 101 or
 102 .I oldset
 103 argument points outside the process's allocated address space.
 104 .TP
 105 .B EINVAL
 106 The value specified in
 107 .I how
 108 was invalid.
 109 .SH CONFORMING TO
 110 POSIX.1-2001.
 111 .SH NOTES
 112 It is not possible to block
 113 .BR SIGKILL " or " SIGSTOP .
 114 Attempts to do so are silently ignored.
 115
 116 Each of the threads in a process has its own signal mask.
 117
 118 A child created via
 119 .BR fork (2)
 120 inherits a copy of its parent's signal mask;
 121 the signal mask is preserved across
 122 .BR execve (2).
 123
 124 If
 125 .BR SIGBUS ,
 126 .BR SIGFPE ,
 127 .BR SIGILL ,
 128 or
 129 .B SIGSEGV
 130 are generated
 131 while they are blocked, the result is undefined,
 132 unless the signal was generated by
 133 .BR kill (2),
 134 .BR sigqueue (3),
 135 or
 136 .BR raise (3).
 137 .PP
 138 See
 139 .BR sigsetops (3)
 140 for details on manipulating signal sets.
 141 .SH SEE ALSO
 142 .BR kill (2),
 143 .BR pause (2),
 144 .BR sigaction (2),
 145 .BR signal (2),
 146 .BR sigpending (2),
 147 .BR sigsuspend (2),
 148 .BR pthread_sigmask (3),
 149 .BR sigqueue (3),
 150 .BR sigsetops (3),
 151 .BR signal (7)