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NAME

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

SYNOPSIS

       #include <signal.h>

       int sigvec(int sig, 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: _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  This API is obsolete: new applications  should  use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 (sigaction(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)();  /* 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; or 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 by default.  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 handler 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  calling  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() function 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) | sigpause(SIGABRT);
                       /* Block SIGQUIT and SIGABRT during
                          handler execution */

       The  sigblock() function adds the signals in mask to the process's signal 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() function returns the signal mask for signum.

ERRORS

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

CONFORMING TO

       All of these functions were in 4.3BSD,  except  siggetmask(),  whose  origin  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.1-2001  leaves  these  aspects  of  signal() unspecified.  See signal(2) for further
       details.

       In order to wait  for  a  signal,  BSD  and  System  V  both  provided  a  function  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

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       project, and information about reporting bugs, can be found at  http://man7.org/linux/man-
       pages/.