man3/sysv_signal.3

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  23 .TH SYSV_SIGNAL 3 2007-05-04 "" "Linux Programmer's Manual"
  24 .SH NAME
  25 sysv_signal \- signal handling with System V semantics
  26 .SH SYNOPSIS
  27 .B #define _GNU_SOURCE
  28 .br
  29 .B #include <signal.h>
  30 .sp
  31 .B typedef void (*sighandler_t)(int);
  32 .sp
  33 .BI "sighandler_t sysv_signal(int " signum ", sighandler_t " handler );
  34 .SH DESCRIPTION
  35 The
  36 .BR sysv_signal ()
  37 function takes the same arguments, and performs the same task, as
  38 .BR signal (2).
  39
  40 However
  41 .BR sysv_signal ()
  42 provides the System V unreliable signal semantics, that is:
  43 a) the disposition of the signal is reset to the default
  44 when the handler is invoked;
  45 b) delivery of further instances of the signal is not blocked while
  46 the signal handler is executing; and
  47 c) if the handler interrupts (certain) blocking system calls,
  48 then the system call is not automatically restarted.
  49 .SH "RETURN VALUE"
  50 The
  51 .BR sysv_signal ()
  52 function returns the previous value of the signal handler, or
  53 .B SIG_ERR
  54 on error.
  55 .SH ERRORS
  56 As for
  57 .BR signal (2).
  58 .SH "CONFORMING TO"
  59 This function is non-standard.
  60 .SH NOTES
  61 Use of
  62 .BR sysv_signal ()
  63 should be avoided; use
  64 .BR sigaction (2)
  65 instead.
  66
  67 On older Linux systems,
  68 .BR sysv_signal ()
  69 and
  70 .BR signal (2)
  71 were equivalent.
  72 But on newer systems,
  73 .BR signal (2)
  74 provides reliable signal semantics; see
  75 .BR signal (2)
  76 for details.
  77
  78 The use of
  79 .B sighandler_t
  80 is a GNU extension;
  81 this type is only defined if
  82 the _GNU_SOURCE feature test macro is defined.
  83 .SH "SEE ALSO"
  84 .BR sigaction (2),
  85 .BR signal (2),
  86 .BR bsd_signal (3),
  87 .BR feature_test_macros (7),
  88 .BR signal (7)