bsd_signal(3) [linux man page]

BSD_SIGNAL(3)						     Linux Programmer's Manual						     BSD_SIGNAL(3)

NAME

       bsd_signal - signal handling with BSD semantics

SYNOPSIS

       #define _XOPEN_SOURCE
       #include <signal.h>

       typedef void (*sighandler_t)(int);

       sighandler_t bsd_signal(int signum, sighandler_t handler);

DESCRIPTION

       The bsd_signal() function takes the same arguments, and performs the same task, as signal(2).

       The  difference between the two is that bsd_signal() is guaranteed to provide reliable signal semantics, that is: a) the disposition of the
       signal is not reset to the default when the handler is invoked; b) delivery of further instances of the signal is blocked while the  signal
       handler is executing; and c) if the handler interrupts a blocking system call, then the system call is automatically restarted.	A portable
       application cannot rely on signal(2) to provide these guarantees.

RETURN VALUE

       The bsd_signal() function returns the previous value of the signal handler, or SIG_ERR on error.

ERRORS

       As for signal(2).

CONFORMING TO

       4.2BSD, POSIX.1-2001.  POSIX.1-2008 removes the specification of bsd_signal(), recommending the use of sigaction(2) instead.

NOTES

       Use of bsd_signal() should be avoided; use sigaction(2) instead.

       On modern Linux systems, bsd_signal() and signal(2) are equivalent.  But on older systems, signal(2) provided unreliable signal	semantics;
       see signal(2) for details.

       The use of sighandler_t is a GNU extension; this type is only defined if the _GNU_SOURCE feature test macro is defined.

SEE ALSO

       sigaction(2), signal(2), sysv_signal(3), feature_test_macros(7), signal(7)

COLOPHON

       This  page is part of release 3.27 of the Linux man-pages project.  A description of the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.

								    2009-03-15							     BSD_SIGNAL(3)

BSD_SIGNAL(3)						   BSD Library Functions Manual 					     BSD_SIGNAL(3)

NAME

     bsd_signal -- simplified signal facilities

SYNOPSIS

     #include <signal.h>

     void (*
     bsd_signal(int sig, void (*func)(int)))(int);

     or in an equivalent but easier to read typedef'd version:

     typedef void (*sig_t) (int);

     sig_t
     bsd_signal(int sig, sig_t func);

DESCRIPTION

     The bsd_signal() function provides a partially compatible interface for programs written to historical system interfaces (see USAGE below).

     The function call bsd_signal(sig, func) has the effect as if implemented as:

	   void (*bsd_signal(int sig, void (*func)(int)))(int)
	   {
	       struct sigaction act, oact;

	       act.sa_handler = func;
	       act.sa_flags = SA_RESTART;
	       sigemptyset(&act.sa_mask);
	       sigaddset(&act.sa_mask, sig);
	       if (sigaction(sig, &act, &oact) == -1)
		   return(SIG_ERR);
	       return(oact.sa_handler);
	   }

     The handler function should be declared:

	   void func(int sig)

     where sig is the signal number.  The behavior is undefined if func() is a function that takes more than one argument, or an argument of a
     different type.

RETURN VALUES

     Upon successful completion, bsd_signal() returns the previous action for sig.  Otherwise, SIG_ERR is returned and errno is set to indicate
     the error.

ERRORS

     Refer to sigaction(2).

USAGE

     This function is a direct replacement for the BSD signal(3) function for simple applications that are installing a single-argument signal
     handler function.	If a BSD signal handler function is being installed that expects more than one argument, the application has to be modi-
     fied to use sigaction(2).	The bsd_signal() function differs from signal(3) in that the SA_RESTART flag is set and the SA_RESETHAND will be
     clear when bsd_signal() is used.  The state of these flags is not specified for signal(3).

SEE ALSO

     sigaction(2), sigaddset(3), sigemptyset(3), signal(3)

STANDARDS

     The bsd_signal() function conforms to IEEE Std 1003.1-2001 (``POSIX.1'').

BSD
								 December 20, 2003							       BSD