man2/sigprocmask.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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  25 .\" 2005-09-15, mtk, Created new page by splitting off from sigaction.2
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  27 .TH SIGPROCMASK 2 2005-09-15 "Linux 2.6.13" "Linux Programmer's Manual"
  28 .SH NAME
  29 sigprocmask \- examine and change blocked signals
  30 .SH SYNOPSIS
  31 .B #include <signal.h>
  32 .sp
  33 .BI "int sigprocmask(int " how ", const sigset_t *" set ,
  34 .BI "sigset_t *" oldset );
  35 .SH DESCRIPTION
  36 .BR sigprocmask ()
  37 is used to change the signal mask, the set of currently blocked signals.
  38 The behaviour of the call is dependent on the value of
  39 .IR how ,
  40 as follows.
  41 .RS
  42 .TP
  43 .B SIG_BLOCK
  44 The set of blocked signals is the union of the current set and the
  45 .I set
  46 argument.
  47 .TP
  48 .B SIG_UNBLOCK
  49 The signals in
  50 .I set
  51 are removed from the current set of blocked signals.  It is legal to
  52 attempt to unblock a signal which is not blocked.
  53 .TP
  54 .B SIG_SETMASK
  55 The set of blocked signals is set to the argument
  56 .IR set .
  57 .RE
  58 .PP
  59 If
  60 .I oldset
  61 is non\-null, the previous value of the signal mask is stored in
  62 .IR oldset .
  63
  64 If
  65 .I set
  66 is NULL, then the signal mask is unchanged (i.e.,
  67 .I how
  68 is ignored),
  69 but the current value of the signal mask is nevertheless returned in
  70 .IR oldset
  71 (it it is not NULL).
  72
  73 The use of
  74 .BR sigprocmask ()
  75 is unspecified in a multithreaded process; see
  76 .BR pthread_sigmask (3).
  77 .SH "RETURN VALUE"
  78 .BR sigprocmask ()
  79 returns 0 on success and \-1 on error.
  80 .SH ERRORS
  81 .B EINVAL
  82 The value specified in
  83 .I how
  84 was invalid.
  85 .SH NOTES
  86 It is not possible to block
  87 .BR SIGKILL " or " SIGSTOP .
  88 Attempts to do so are silently ignored.
  89 .PP
  90 If
  91 .BR SIGBUS ,
  92 .BR SIGFPE ,
  93 .BR SIGILL ,
  94 or
  95 .BR SIGSEGV
  96 are generated
  97 while they are blocked, the result is undefined,
  98 unless the signal was generated by the
  99 .BR kill (2),
 100 .BR sigqueue (2),
 101 or
 102 .BR raise (3).
 103 .PP
 104 See
 105 .BR sigsetops (3)
 106 for details on manipulating signal sets.
 107 .SH "CONFORMING TO"
 108 POSIX.1-2001.
 109 .SH "SEE ALSO"
 110 .BR kill (2),
 111 .BR pause (2),
 112 .BR sigaction (2),
 113 .BR signal (2),
 114 .BR sigpending (2),
 115 .BR sigprocmask (2),
 116 .BR sigqueue (2),
 117 .BR sigsuspend (2),
 118 .BR pthread_sigmask (3),
 119 .BR sigsetops (3),
 120 .BR signal (7)