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  This API is obsolete: new  applications  should  use  the  POSIX  signal  API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)(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 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

       This  page  is  part  of  release 3.54 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/.