man3/sysv_signal.3

   1 .\" Copyright (c) 2007 Michael Kerrisk <mtk.manpages@gmail.com>
   2 .\"
   3 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
   4 .\"
   5 .TH SYSV_SIGNAL 3 2021-03-22 "Linux man-pages (unreleased)"
   6 .SH NAME
   7 sysv_signal \- signal handling with System V semantics
   8 .SH LIBRARY
   9 Standard C library
  10 .RI ( libc ", " \-lc )
  11 .SH SYNOPSIS
  12 .nf
  13 .BR "#define _GNU_SOURCE" "         /* See feature_test_macros(7) */"
  14 .B #include <signal.h>
  15 .PP
  16 .B typedef void (*sighandler_t)(int);
  17 .PP
  18 .BI "sighandler_t sysv_signal(int " signum ", sighandler_t " handler );
  19 .fi
  20 .SH DESCRIPTION
  21 The
  22 .BR sysv_signal ()
  23 function takes the same arguments, and performs the same task, as
  24 .BR signal (2).
  25 .PP
  26 However
  27 .BR sysv_signal ()
  28 provides the System V unreliable signal semantics, that is:
  29 a) the disposition of the signal is reset to the default
  30 when the handler is invoked;
  31 b) delivery of further instances of the signal is not blocked while
  32 the signal handler is executing; and
  33 c) if the handler interrupts (certain) blocking system calls,
  34 then the system call is not automatically restarted.
  35 .SH RETURN VALUE
  36 The
  37 .BR sysv_signal ()
  38 function returns the previous value of the signal handler, or
  39 .B SIG_ERR
  40 on error.
  41 .SH ERRORS
  42 As for
  43 .BR signal (2).
  44 .SH ATTRIBUTES
  45 For an explanation of the terms used in this section, see
  46 .BR attributes (7).
  47 .ad l
  48 .nh
  49 .TS
  50 allbox;
  51 lbx lb lb
  52 l l l.
  53 Interface       Attribute       Value
  54 T{
  55 .BR sysv_signal ()
  56 T}      Thread safety   MT-Safe
  57 .TE
  58 .hy
  59 .ad
  60 .sp 1
  61 .SH STANDARDS
  62 This function is nonstandard.
  63 .SH NOTES
  64 Use of
  65 .BR sysv_signal ()
  66 should be avoided; use
  67 .BR sigaction (2)
  68 instead.
  69 .PP
  70 On older Linux systems,
  71 .BR sysv_signal ()
  72 and
  73 .BR signal (2)
  74 were equivalent.
  75 But on newer systems,
  76 .BR signal (2)
  77 provides reliable signal semantics; see
  78 .BR signal (2)
  79 for details.
  80 .PP
  81 The use of
  82 .I sighandler_t
  83 is a GNU extension;
  84 this type is defined only if
  85 the
  86 .B _GNU_SOURCE
  87 feature test macro is defined.
  88 .SH SEE ALSO
  89 .BR sigaction (2),
  90 .BR signal (2),
  91 .BR bsd_signal (3),
  92 .BR signal (7)