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, 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 sig-
       nal 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  This API is obsolete: new applications should use the POSIX signal API (sigaction(2), sigprocmask(2), etc.)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  with-
       out 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 speci-
              fied, 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_SET-
       MASK)), 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 sig-
       nal(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  dif-
       ferent 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 3.25 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/.



Linux                                                      2007-07-26                                                  SIGVEC(3)