man3/bsd_signal.3

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  23 .TH BSD_SIGNAL 2 2007-05-04 "" "Linux Programmer's Manual"
  24 .SH NAME
  25 bsd_signal \- signal handling with BSD semantics
  26 .SH SYNOPSIS
  27 .B #define _XOPEN_SOURCE
  28 .br
  29 .B #include <signal.h>
  30 .sp
  31 .B typedef void (*sighandler_t)(int);
  32 .sp
  33 .BI "sighandler_t bsd_signal(int " signum ", sighandler_t " handler );
  34 .SH DESCRIPTION
  35 The
  36 .BR bsd_signal ()
  37 function takes the same arguments, and performs the same task, as
  38 .BR signal (2).
  39
  40 The difference between the two is that
  41 .BR bsd_signal ()
  42 is guaranteed to provide reliable signal semantics, that is:
  43 a) the disposition of the signal is not reset to the default
  44 when the handler is invoked;
  45 b) delivery of further instances of the signal is blocked while
  46 the signal handler is executing; and
  47 c) if the handler interrupts a blocking system call,
  48 then the system call is automatically restarted.
  49 A portable application cannot rely on
  50 .BR signal (2)
  51 to provide these guarantees.
  52 .SH "RETURN VALUE"
  53 The
  54 .BR bsd_signal ()
  55 function returns the previous value of the signal handler, or
  56 .B SIG_ERR
  57 on error.
  58 .SH ERRORS
  59 As for
  60 .BR signal (2).
  61 .SH NOTES
  62 Use of
  63 .BR bsd_signal ()
  64 should be avoided; use
  65 .BR sigaction (2)
  66 instead.
  67
  68 On modern Linux systems,
  69 .BR bsd_signal ()
  70 and
  71 .BR signal (2)
  72 are equivalent.
  73 But on older systems,
  74 .BR signal (2)
  75 provided unreliable signal semantics; see
  76 .BR signal (2)
  77 for details.
  78
  79 The use of
  80 .B sighandler_t
  81 is a GNU extension;
  82 this type is only defined if
  83 the _GNU_SOURCE feature test macro is defined.
  84 .SH "CONFORMING TO"
  85 4.2BSD, POSIX.1-2001.
  86 .SH "SEE ALSO"
  87 .BR sigaction (2),
  88 .BR signal (2),
  89 .BR sysv_signal (3),
  90 .BR feature_test_macros (7),
  91 .BR signal (7)