man3/sysv_signal.3

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  25 .TH SYSV_SIGNAL 3 2017-09-15 "" "Linux Programmer's Manual"
  26 .SH NAME
  27 sysv_signal \- signal handling with System V semantics
  28 .SH SYNOPSIS
  29 .BR "#define _GNU_SOURCE" "         /* See feature_test_macros(7) */"
  30 .br
  31 .B #include <signal.h>
  32 .PP
  33 .B typedef void (*sighandler_t)(int);
  34 .PP
  35 .BI "sighandler_t sysv_signal(int " signum ", sighandler_t " handler );
  36 .SH DESCRIPTION
  37 The
  38 .BR sysv_signal ()
  39 function takes the same arguments, and performs the same task, as
  40 .BR signal (2).
  41 .PP
  42 However
  43 .BR sysv_signal ()
  44 provides the System V unreliable signal semantics, that is:
  45 a) the disposition of the signal is reset to the default
  46 when the handler is invoked;
  47 b) delivery of further instances of the signal is not blocked while
  48 the signal handler is executing; and
  49 c) if the handler interrupts (certain) blocking system calls,
  50 then the system call is not automatically restarted.
  51 .SH RETURN VALUE
  52 The
  53 .BR sysv_signal ()
  54 function returns the previous value of the signal handler, or
  55 .B SIG_ERR
  56 on error.
  57 .SH ERRORS
  58 As for
  59 .BR signal (2).
  60 .SH ATTRIBUTES
  61 For an explanation of the terms used in this section, see
  62 .BR attributes (7).
  63 .TS
  64 allbox;
  65 lb lb lb
  66 l l l.
  67 Interface       Attribute       Value
  68 T{
  69 .BR sysv_signal ()
  70 T}      Thread safety   MT-Safe
  71 .TE
  72 .SH CONFORMING TO
  73 This function is nonstandard.
  74 .SH NOTES
  75 Use of
  76 .BR sysv_signal ()
  77 should be avoided; use
  78 .BR sigaction (2)
  79 instead.
  80 .PP
  81 On older Linux systems,
  82 .BR sysv_signal ()
  83 and
  84 .BR signal (2)
  85 were equivalent.
  86 But on newer systems,
  87 .BR signal (2)
  88 provides reliable signal semantics; see
  89 .BR signal (2)
  90 for details.
  91 .PP
  92 The use of
  93 .I sighandler_t
  94 is a GNU extension;
  95 this type is defined only if
  96 the
  97 .B _GNU_SOURCE
  98 feature test macro is defined.
  99 .SH SEE ALSO
 100 .BR sigaction (2),
 101 .BR signal (2),
 102 .BR bsd_signal (3),
 103 .BR signal (7)