sigvec

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, const 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:
           Since glibc 2.19:
               _DEFAULT_SOURCE
           Glibc 2.19 and earlier:
               _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  This  API  is
       obsolete:  new  applications  should  use  the POSIX signal API (sigac-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
       sv_flags field specifies flags controlling what happens when  the  han-
       dler  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 s not be restarted:
              instead it fails 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 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() macro 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) | sigmask(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() macro returns the signal mask for signum.

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

VERSIONS
       Starting with version 2.21, the GNU C library  no  longer  exports  the
       sigvec()  function as part of the ABI.  (To ensure backward compatibil-
       ity, the glibc symbol versioning scheme continues to export the  inter-
       face to binaries linked against older versions of the library.)

ATTRIBUTES
       For   an   explanation   of   the  terms  used  in  this  section,  see
       attributes(7).

       +---------------------------------+---------------+---------+
       |Interface                        | Attribute     | Value   |
       +---------------------------------+---------------+---------+
       |sigvec(), sigmask(), sigblock(), | Thread safety | MT-Safe |
       |sigsetmask(), siggetmask()       |               |         |
       +---------------------------------+---------------+---------+
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 leaves these aspects of sig-
       nal() unspecified.  See signal(2) for further details.

       In order to wait for a signal, BSD and System V both provided  a  func-
       tion  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 4.15 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest     version     of     this    page,    can    be    found    at
       https://www.kernel.org/doc/man-pages/.

Linux                             2017-09-15                         SIGVEC(3)
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