sigblock


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  This  API  is
       obsolete:  new  applications  should  use  the POSIX signal API (sigac-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
              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()  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 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() 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 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.1-2001 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  func-


Linux                             2012-09-06                         SIGVEC(3)
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