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



NAME
       sigvec, sigblock, sigsetmask, siggetmask, sigmask - BSD signal API

SYNOPSIS
       #include <signal.h>

       int sigvec(int sig, const struct sigvec *vec, struct sigvec *ovec);

       int sigmask(int signum);

       int sigblock(int mask);

       int sigsetmask(int mask);

       int siggetmask(void);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       All functions shown above:
	   Since glibc 2.19:
	       _DEFAULT_SOURCE
	   Glibc 2.19 and earlier:
	       _BSD_SOURCE

DESCRIPTION
       These  functions are provided in glibc as a compatibility interface for
       programs that make use of the historical BSD signal API.	 This  API  is
       obsolete:  new  applications  should  use  the POSIX signal API (sigac-
       tion(2), sigprocmask(2), etc.).

       The sigvec() function sets and/or gets the disposition  of  the	signal
       sig  (like the POSIX sigaction(2)).  If vec is not NULL, it points to a
       sigvec structure that defines the new disposition for sig.  If ovec  is
       not  NULL,  it  points to a sigvec structure that is used to return the
       previous disposition of sig.  To obtain the current disposition of  sig
       without	changing  it, specify NULL for vec, and a non-null pointer for
       ovec.

       The dispositions for SIGKILL and SIGSTOP cannot be changed.

       The sigvec structure has the following form:

	   struct sigvec {
	       void (*sv_handler)(int); /* Signal disposition */
	       int    sv_mask;		/* Signals to be blocked in handler */
	       int    sv_flags;		/* Flags */
	   };

       The sv_handler field specifies the disposition of the  signal,  and  is
       either:	the address of a signal handler function; SIG_DFL, meaning the
       default disposition applies for the signal; or  SIG_IGN,	 meaning  that
       the signal is ignored.

       If  sv_handler  specifies the address of a signal handler, then sv_mask
       specifies a mask of signals that are to be blocked while the handler is
       executing.  In addition, the signal for which the handler is invoked is
       also blocked.  Attempts	to  block  SIGKILL  or	SIGSTOP	 are  silently
       ignored.

       If  sv_handler  specifies  the  address	of  a signal handler, then the
       sv_flags field specifies flags controlling what happens when  the  han-
       dler  is	 called.  This field may contain zero or more of the following
       flags:

       SV_INTERRUPT
	      If the signal handler interrupts a blocking  system  call,  then
	      upon  return  from  the  handler	the  system  call  will not be
	      restarted: instead it will fail with the error EINTR.   If  this
	      flag  is	not  specified,	 then  system  calls  are restarted by
	      default.

       SV_RESETHAND
	      Reset the disposition of the signal to the default before	 call-
	      ing the signal handler.  If this flag is not specified, then the
	      handler remains established until explicitly removed by a	 later
	      call to sigvec() or until the process performs an execve(2).

       SV_ONSTACK
	      Handle  the  signal  on the alternate signal stack (historically
	      established under BSD using the  obsolete	 sigstack()  function;
	      the POSIX replacement is sigaltstack(2)).

       The  sigmask() macro constructs and returns a "signal mask" for signum.
       For example, we can initialize the vec.sv_mask field given to  sigvec()
       using code such as the following:

	   vec.sv_mask = sigmask(SIGQUIT) | sigmask(SIGABRT);
		       /* Block SIGQUIT and SIGABRT during
			  handler execution */

       The  sigblock() function adds the signals in mask to the process's sig-
       nal mask (like POSIX sigprocmask(SIG_BLOCK)), and returns the process's
       previous	 signal	 mask.	 Attempts  to  block  SIGKILL  or  SIGSTOP are
       silently ignored.

       The sigsetmask() function sets the process's signal mask to  the	 value
       given  in  mask	(like POSIX sigprocmask(SIG_SETMASK)), and returns the
       process's previous signal mask.

       The siggetmask() function returns the process's	current	 signal	 mask.
       This call is equivalent to sigblock(0).

RETURN VALUE
       The sigvec() function returns 0 on success; on error, it returns -1 and
       sets errno to indicate the error.

       The sigblock() and sigsetmask() functions return	 the  previous	signal
       mask.

       The sigmask() macro returns the signal mask for signum.

ERRORS
       See the ERRORS under sigaction(2) and sigprocmask(2).

VERSIONS
       Starting	 with  version	2.21,  the GNU C library no longer exports the
       sigvec() function as part of the ABI.  (To ensure backward  compatibil-
       ity,  the glibc symbol versioning scheme continues to export the inter-
       face to binaries linked against older versions of the library.)

ATTRIBUTES
       For  an	explanation  of	 the  terms  used   in	 this	section,   see
       attributes(7).

       +---------------------------------+---------------+---------+
       |Interface			 | Attribute	 | Value   |
       +---------------------------------+---------------+---------+
       |sigvec(), sigmask(), sigblock(), | Thread safety | MT-Safe |
       |sigsetmask(), siggetmask()	 |		 |	   |
       +---------------------------------+---------------+---------+
CONFORMING TO
       All of these functions were in 4.3BSD, except siggetmask(), whose  ori-
       gin  is	unclear.  These functions are obsolete: do not use them in new
       programs.

NOTES
       On 4.3BSD, the signal() function provided reliable semantics  (as  when
       calling	sigvec()  with vec.sv_mask equal to 0).	 On System V, signal()
       provides unreliable semantics.  POSIX.1 leaves these  aspects  of  sig-
       nal() unspecified.  See signal(2) for further details.

       In  order  to wait for a signal, BSD and System V both provided a func-
       tion named sigpause(3), but this function has a different  argument  on
       the two systems.	 See sigpause(3) for details.

SEE ALSO
       kill(2),	 pause(2),  sigaction(2), signal(2), sigprocmask(2), raise(3),
       sigpause(3), sigset(3), signal(7)

COLOPHON
       This page is part of release 4.10 of the Linux  man-pages  project.   A
       description  of	the project, information about reporting bugs, and the
       latest	 version    of	  this	  page,	   can	   be	  found	    at
       https://www.kernel.org/doc/man-pages/.



Linux				  2016-10-08			     SIGVEC(3)