man3/bsd_signal.3

   1 .\" Copyright (c) 2007 Michael Kerrisk <mtk.manpages@gmail.com>
   2 .\"
   3 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
   4 .\"
   5 .TH bsd_signal 3 (date) "Linux man-pages (unreleased)"
   6 .SH NAME
   7 bsd_signal \- signal handling with BSD semantics
   8 .SH LIBRARY
   9 Standard C library
  10 .RI ( libc ", " \-lc )
  11 .SH SYNOPSIS
  12 .nf
  13 .B #include <signal.h>
  14 .PP
  15 .B typedef void (*sighandler_t)(int);
  16 .PP
  17 .BI "sighandler_t bsd_signal(int " signum ", sighandler_t " handler );
  18 .fi
  19 .PP
  20 .RS -4
  21 Feature Test Macro Requirements for glibc (see
  22 .BR feature_test_macros (7)):
  23 .RE
  24 .PP
  25 .BR bsd_signal ():
  26 .nf
  27     Since glibc 2.26:
  28         _XOPEN_SOURCE >= 500
  29 .\"    || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
  30             && ! (_POSIX_C_SOURCE >= 200809L)
  31     Glibc 2.25 and earlier:
  32         _XOPEN_SOURCE
  33 .fi
  34 .SH DESCRIPTION
  35 The
  36 .BR bsd_signal ()
  37 function takes the same arguments, and performs the same task, as
  38 .BR signal (2).
  39 .PP
  40 The difference between the two is that
  41 .BR bsd_signal ()
  42 is guaranteed to provide reliable signal semantics, that is:
  43 a) the disposition of the signal is not reset to the default
  44 when the handler is invoked;
  45 b) delivery of further instances of the signal is blocked while
  46 the signal handler is executing; and
  47 c) if the handler interrupts a blocking system call,
  48 then the system call is automatically restarted.
  49 A portable application cannot rely on
  50 .BR signal (2)
  51 to provide these guarantees.
  52 .SH RETURN VALUE
  53 The
  54 .BR bsd_signal ()
  55 function returns the previous value of the signal handler, or
  56 .B SIG_ERR
  57 on error.
  58 .SH ERRORS
  59 As for
  60 .BR signal (2).
  61 .SH ATTRIBUTES
  62 For an explanation of the terms used in this section, see
  63 .BR attributes (7).
  64 .ad l
  65 .nh
  66 .TS
  67 allbox;
  68 lbx lb lb
  69 l l l.
  70 Interface       Attribute       Value
  71 T{
  72 .BR bsd_signal ()
  73 T}      Thread safety   MT-Safe
  74 .TE
  75 .hy
  76 .ad
  77 .sp 1
  78 .SH STANDARDS
  79 4.2BSD, POSIX.1-2001.
  80 POSIX.1-2008 removes the specification of
  81 .BR bsd_signal (),
  82 recommending the use of
  83 .BR sigaction (2)
  84 instead.
  85 .SH NOTES
  86 Use of
  87 .BR bsd_signal ()
  88 should be avoided; use
  89 .BR sigaction (2)
  90 instead.
  91 .PP
  92 On modern Linux systems,
  93 .BR bsd_signal ()
  94 and
  95 .BR signal (2)
  96 are equivalent.
  97 But on older systems,
  98 .BR signal (2)
  99 provided unreliable signal semantics; see
 100 .BR signal (2)
 101 for details.
 102 .PP
 103 The use of
 104 .I sighandler_t
 105 is a GNU extension;
 106 this type is defined only if the
 107 .B _GNU_SOURCE
 108 feature test macro is defined.
 109 .SH SEE ALSO
 110 .BR sigaction (2),
 111 .BR signal (2),
 112 .BR sysv_signal (3),
 113 .BR signal (7)