man3/bsd_signal.3

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  25 .TH BSD_SIGNAL 3 2015-03-02 "" "Linux Programmer's Manual"
  26 .SH NAME
  27 bsd_signal \- signal handling with BSD semantics
  28 .SH SYNOPSIS
  29 .BR "#define _XOPEN_SOURCE" "       /* See feature_test_macros(7) */"
  30 .br
  31 .B #include <signal.h>
  32 .sp
  33 .B typedef void (*sighandler_t)(int);
  34 .sp
  35 .BI "sighandler_t bsd_signal(int " signum ", sighandler_t " handler );
  36 .SH DESCRIPTION
  37 The
  38 .BR bsd_signal ()
  39 function takes the same arguments, and performs the same task, as
  40 .BR signal (2).
  41
  42 The difference between the two is that
  43 .BR bsd_signal ()
  44 is guaranteed to provide reliable signal semantics, that is:
  45 a) the disposition of the signal is not reset to the default
  46 when the handler is invoked;
  47 b) delivery of further instances of the signal is blocked while
  48 the signal handler is executing; and
  49 c) if the handler interrupts a blocking system call,
  50 then the system call is automatically restarted.
  51 A portable application cannot rely on
  52 .BR signal (2)
  53 to provide these guarantees.
  54 .SH RETURN VALUE
  55 The
  56 .BR bsd_signal ()
  57 function returns the previous value of the signal handler, or
  58 .B SIG_ERR
  59 on error.
  60 .SH ERRORS
  61 As for
  62 .BR signal (2).
  63 .SH ATTRIBUTES
  64 For an explanation of the terms used in this section, see
  65 .BR attributes (7).
  66 .TS
  67 allbox;
  68 lb 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 .SH CONFORMING TO
  76 4.2BSD, POSIX.1-2001.
  77 POSIX.1-2008 removes the specification of
  78 .BR bsd_signal (),
  79 recommending the use of
  80 .BR sigaction (2)
  81 instead.
  82 .SH NOTES
  83 Use of
  84 .BR bsd_signal ()
  85 should be avoided; use
  86 .BR sigaction (2)
  87 instead.
  88
  89 On modern Linux systems,
  90 .BR bsd_signal ()
  91 and
  92 .BR signal (2)
  93 are equivalent.
  94 But on older systems,
  95 .BR signal (2)
  96 provided unreliable signal semantics; see
  97 .BR signal (2)
  98 for details.
  99
 100 The use of
 101 .I sighandler_t
 102 is a GNU extension;
 103 this type is defined only if the
 104 .B _GNU_SOURCE
 105 feature test macro is defined.
 106 .SH SEE ALSO
 107 .BR sigaction (2),
 108 .BR signal (2),
 109 .BR sysv_signal (3),
 110 .BR signal (7)