man3/bsd_signal.3

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  25 .TH BSD_SIGNAL 3 2017-07-13 "" "Linux Programmer's Manual"
  26 .SH NAME
  27 bsd_signal \- signal handling with BSD semantics
  28 .SH SYNOPSIS
  29 .B #include <signal.h>
  30 .PP
  31 .B typedef void (*sighandler_t)(int);
  32 .PP
  33 .BI "sighandler_t bsd_signal(int " signum ", sighandler_t " handler );
  34 .PP
  35 .in -4n
  36 Feature Test Macro Requirements for glibc (see
  37 .BR feature_test_macros (7)):
  38 .in
  39 .PP
  40 .ad l
  41 .BR bsd_signal ():
  42 .RS 4
  43 Since glibc 2.26:
  44     _XOPEN_SOURCE >= 500
  45 .\"    || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
  46         && ! (_POSIX_C_SOURCE\ >=\ 200112L)
  47 .br
  48 Glibc 2.25 and earlier:
  49     _XOPEN_SOURCE
  50 .RE
  51 .ad b
  52 .SH DESCRIPTION
  53 The
  54 .BR bsd_signal ()
  55 function takes the same arguments, and performs the same task, as
  56 .BR signal (2).
  57 .PP
  58 The difference between the two is that
  59 .BR bsd_signal ()
  60 is guaranteed to provide reliable signal semantics, that is:
  61 a) the disposition of the signal is not reset to the default
  62 when the handler is invoked;
  63 b) delivery of further instances of the signal is blocked while
  64 the signal handler is executing; and
  65 c) if the handler interrupts a blocking system call,
  66 then the system call is automatically restarted.
  67 A portable application cannot rely on
  68 .BR signal (2)
  69 to provide these guarantees.
  70 .SH RETURN VALUE
  71 The
  72 .BR bsd_signal ()
  73 function returns the previous value of the signal handler, or
  74 .B SIG_ERR
  75 on error.
  76 .SH ERRORS
  77 As for
  78 .BR signal (2).
  79 .SH ATTRIBUTES
  80 For an explanation of the terms used in this section, see
  81 .BR attributes (7).
  82 .TS
  83 allbox;
  84 lb lb lb
  85 l l l.
  86 Interface       Attribute       Value
  87 T{
  88 .BR bsd_signal ()
  89 T}      Thread safety   MT-Safe
  90 .TE
  91 .SH CONFORMING TO
  92 4.2BSD, POSIX.1-2001.
  93 POSIX.1-2008 removes the specification of
  94 .BR bsd_signal (),
  95 recommending the use of
  96 .BR sigaction (2)
  97 instead.
  98 .SH NOTES
  99 Use of
 100 .BR bsd_signal ()
 101 should be avoided; use
 102 .BR sigaction (2)
 103 instead.
 104 .PP
 105 On modern Linux systems,
 106 .BR bsd_signal ()
 107 and
 108 .BR signal (2)
 109 are equivalent.
 110 But on older systems,
 111 .BR signal (2)
 112 provided unreliable signal semantics; see
 113 .BR signal (2)
 114 for details.
 115 .PP
 116 The use of
 117 .I sighandler_t
 118 is a GNU extension;
 119 this type is defined only if the
 120 .B _GNU_SOURCE
 121 feature test macro is defined.
 122 .SH SEE ALSO
 123 .BR sigaction (2),
 124 .BR signal (2),
 125 .BR sysv_signal (3),
 126 .BR signal (7)