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  This  API  is
       obsolete:   new   applications   should   use   the  POSIX  signal  API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