Python signal.SIG_DFL Examples

def __call__(self, *args, **kwargs):
        """Trap ``SIGTERM`` and call wrapped function."""
        self._caught_signal = None
        # Register handler for SIGTERM, then call `self.func`
        self.old_signal_handler = signal.getsignal(signal.SIGTERM)
        signal.signal(signal.SIGTERM, self.signal_handler)

        self.func(*args, **kwargs)

        # Restore old signal handler
        signal.signal(signal.SIGTERM, self.old_signal_handler)

        # Handle any signal caught during execution
        if self._caught_signal is not None:
            signum, frame = self._caught_signal
            if callable(self.old_signal_handler):
                self.old_signal_handler(signum, frame)
            elif self.old_signal_handler == signal.SIG_DFL:
                sys.exit(0) 

def __init__(self):
        # Setup signal fd, this allows signal to behave correctly
        if os.name == 'posix':
            self.signal_pipe_r, self.signal_pipe_w = os.pipe()
            self._set_nonblock(self.signal_pipe_r)
            self._set_nonblock(self.signal_pipe_w)
            signal.set_wakeup_fd(self.signal_pipe_w)

        self._signals_received = collections.deque()

        signal.signal(signal.SIGINT, signal.SIG_DFL)
        if os.name == 'posix':
            signal.signal(signal.SIGCHLD, signal.SIG_DFL)
            signal.signal(signal.SIGTERM, self._signal_catcher)
            signal.signal(signal.SIGALRM, self._signal_catcher)
            signal.signal(signal.SIGHUP, self._signal_catcher)
        else:
            # currently a noop on window...
            signal.signal(signal.SIGTERM, self._signal_catcher)
            # FIXME(sileht): should allow to catch signal CTRL_BREAK_EVENT,
            # but we to create the child process with CREATE_NEW_PROCESS_GROUP
            # to make this work, so current this is a noop for later fix
            signal.signal(signal.SIGBREAK, self._signal_catcher) 

def __call__(self, *args, **kwargs):
        """Trap ``SIGTERM`` and call wrapped function."""
        self._caught_signal = None
        # Register handler for SIGTERM, then call `self.func`
        self.old_signal_handler = signal.getsignal(signal.SIGTERM)
        signal.signal(signal.SIGTERM, self.signal_handler)

        self.func(*args, **kwargs)

        # Restore old signal handler
        signal.signal(signal.SIGTERM, self.old_signal_handler)

        # Handle any signal caught during execution
        if self._caught_signal is not None:
            signum, frame = self._caught_signal
            if callable(self.old_signal_handler):
                self.old_signal_handler(signum, frame)
            elif self.old_signal_handler == signal.SIG_DFL:
                sys.exit(0) 

def __call__(self, *args, **kwargs):
        self._caught_signal = None
        # Register handler for SIGTERM, then call `self.func`
        self.old_signal_handler = signal.getsignal(signal.SIGTERM)
        signal.signal(signal.SIGTERM, self.signal_handler)

        self.func(*args, **kwargs)

        # Restore old signal handler
        signal.signal(signal.SIGTERM, self.old_signal_handler)

        # Handle any signal caught during execution
        if self._caught_signal is not None:
            signum, frame = self._caught_signal
            if callable(self.old_signal_handler):
                self.old_signal_handler(signum, frame)
            elif self.old_signal_handler == signal.SIG_DFL:
                sys.exit(0) 

def __call__(self, *args, **kwargs):
        self._caught_signal = None
        # Register handler for SIGTERM, then call `self.func`
        self.old_signal_handler = signal.getsignal(signal.SIGTERM)
        signal.signal(signal.SIGTERM, self.signal_handler)

        self.func(*args, **kwargs)

        # Restore old signal handler
        signal.signal(signal.SIGTERM, self.old_signal_handler)

        # Handle any signal caught during execution
        if self._caught_signal is not None:
            signum, frame = self._caught_signal
            if callable(self.old_signal_handler):
                self.old_signal_handler(signum, frame)
            elif self.old_signal_handler == signal.SIG_DFL:
                sys.exit(0) 

def main():
    # make sure CTRL+C works
    signal.signal(signal.SIGINT, signal.SIG_DFL)

    description = """BlitzTUI - the Touch-User-Interface for the RaspiBlitz project

Keep on stacking SATs..! :-D"""

    parser = argparse.ArgumentParser(description=description, formatter_class=RawTextHelpFormatter)
    parser.add_argument("-V", "--version",
                        help="print version", action="version",
                        version=__version__)

    parser.add_argument('-d', '--debug', help="enable debug logging", action="store_true")

    # parse args
    args = parser.parse_args()

    if args.debug:
        setup_logging(log_level="DEBUG")
    else:
        setup_logging()

    log.info("Starting BlitzTUI v{}".format(__version__))

    # initialize app
    app = QApplication(sys.argv)

    w = AppWindow()
    w.show()

    # run app
    sys.exit(app.exec_()) 

def __call__(self, *args, **kwargs):
        self._caught_signal = None
        # Register handler for SIGTERM, then call `self.func`
        self.old_signal_handler = signal.getsignal(signal.SIGTERM)
        signal.signal(signal.SIGTERM, self.signal_handler)

        self.func(*args, **kwargs)

        # Restore old signal handler
        signal.signal(signal.SIGTERM, self.old_signal_handler)

        # Handle any signal caught during execution
        if self._caught_signal is not None:
            signum, frame = self._caught_signal
            if callable(self.old_signal_handler):
                self.old_signal_handler(signum, frame)
            elif self.old_signal_handler == signal.SIG_DFL:
                sys.exit(0) 

def __init__(self, default_handler):
        self.called = False
        self.original_handler = default_handler
        if isinstance(default_handler, int):
            if default_handler == signal.SIG_DFL:
                # Pretend it's signal.default_int_handler instead.
                default_handler = signal.default_int_handler
            elif default_handler == signal.SIG_IGN:
                # Not quite the same thing as SIG_IGN, but the closest we
                # can make it: do nothing.
                def default_handler(unused_signum, unused_frame):
                    pass
            else:
                raise TypeError("expected SIGINT signal handler to be "
                                "signal.SIG_IGN, signal.SIG_DFL, or a "
                                "callable object")
        self.default_handler = default_handler 

def closeConnections(self):
        try:
            self.workerSocket.shutdown(socket.SHUT_RDWR)
        except:
            pass
        try:
            self.workerSocket.close()
        except:
            pass
        try:
            self.clientSocket.shutdown(socket.SHUT_RDWR)
        except:
            pass
        try:
            self.clientSocket.close()
        except:
            pass
        signal.signal(signal.SIGTERM, signal.SIG_DFL) 

def __call__(self, *args, **kwargs):
        """Trap ``SIGTERM`` and call wrapped function."""
        self._caught_signal = None
        # Register handler for SIGTERM, then call `self.func`
        self.old_signal_handler = signal.getsignal(signal.SIGTERM)
        signal.signal(signal.SIGTERM, self.signal_handler)

        self.func(*args, **kwargs)

        # Restore old signal handler
        signal.signal(signal.SIGTERM, self.old_signal_handler)

        # Handle any signal caught during execution
        if self._caught_signal is not None:
            signum, frame = self._caught_signal
            if callable(self.old_signal_handler):
                self.old_signal_handler(signum, frame)
            elif self.old_signal_handler == signal.SIG_DFL:
                sys.exit(0) 

def unsubscribe(self):
        """Unsubscribe self.handlers from signals."""
        for signum, handler in self._previous_handlers.items():
            signame = self.signals[signum]

            if handler is None:
                self.bus.log('Restoring %s handler to SIG_DFL.' % signame)
                handler = _signal.SIG_DFL
            else:
                self.bus.log('Restoring %s handler %r.' % (signame, handler))

            try:
                our_handler = _signal.signal(signum, handler)
                if our_handler is None:
                    self.bus.log('Restored old %s handler %r, but our '
                                 'handler was not registered.' %
                                 (signame, handler), level=30)
            except ValueError:
                self.bus.log('Unable to restore %s handler %r.' %
                             (signame, handler), level=40, traceback=True) 

def context(**handlers):
    signals = {}

    def handler(signum, frame):
        signame = SIGNAL_NAMES[signum]
        signals[signame] = True
        handler = handlers[signame]
        handler()

    def set_all(handler):
        for signame in handlers:
            if signame in SIGNAL_NUMBERS:  # Windows doesn't have all signals
                signal.signal(SIGNAL_NUMBERS[signame], handler)

    set_all(handler)
    try:
        yield signals

    finally:
        set_all(signal.SIG_DFL) 

def setUp(self):
        """
        Save the current SIGCHLD handler as reported by L{signal.signal} and
        the current file descriptor registered with L{installHandler}.
        """
        handler = signal.getsignal(signal.SIGCHLD)
        if handler != signal.SIG_DFL:
            self.signalModuleHandler = handler
            signal.signal(signal.SIGCHLD, signal.SIG_DFL)
        else:
            self.signalModuleHandler = None

        self.oldFD = installHandler(-1)

        if self.signalModuleHandler is not None and self.oldFD != -1:
            msg("Previous test didn't clean up after its SIGCHLD setup: %r %r"
                % (self.signalModuleHandler, self.oldFD)) 

def installHandler(fd):
    """
    Install a signal handler which will write a byte to C{fd} when
    I{SIGCHLD} is received.

    This is implemented by installing a SIGCHLD handler that does nothing,
    setting the I{SIGCHLD} handler as not allowed to interrupt system calls,
    and using L{signal.set_wakeup_fd} to do the actual writing.

    @param fd: The file descriptor to which to write when I{SIGCHLD} is
        received.
    @type fd: C{int}
    """
    if fd == -1:
        signal.signal(signal.SIGCHLD, signal.SIG_DFL)
    else:
        def noopSignalHandler(*args):
            pass
        signal.signal(signal.SIGCHLD, noopSignalHandler)
        signal.siginterrupt(signal.SIGCHLD, False)
    return signal.set_wakeup_fd(fd) 

def _downloadLocalFile(self, key, suffix):
        # Set default signal handler so that KeyboardInterrupt is raised.
        # Needed to gracefully handle ctrl+c.
        signal.signal(signal.SIGINT, signal.default_int_handler)

        try:
            with self._openDownloadFile(key, suffix) as (name, fileobj):
                ret = readFileOrHandle(name, fileobj)
            return (ret, None, None)
        except ArtifactNotFoundError:
            return (None, "not found", WARNING)
        except ArtifactDownloadError as e:
            return (None, e.reason, WARNING)
        except BuildError as e:
            raise
        except OSError as e:
            raise BuildError("Cannot download file: " + str(e))
        finally:
            # Restore signals to default so that Ctrl+C kills process. Needed
            # to prevent ugly backtraces when user presses ctrl+c.
            signal.signal(signal.SIGINT, signal.SIG_DFL) 

def _uploadPackage(self, buildId, suffix, audit, content):
        # Set default signal handler so that KeyboardInterrupt is raised.
        # Needed to gracefully handle ctrl+c.
        signal.signal(signal.SIGINT, signal.default_int_handler)

        try:
            with self._openUploadFile(buildId, suffix) as (name, fileobj):
                pax = { 'bob-archive-vsn' : "1" }
                with gzip.open(name or fileobj, 'wb', 6) as gzf:
                    with tarfile.open(name, "w", fileobj=gzf,
                                      format=tarfile.PAX_FORMAT, pax_headers=pax) as tar:
                        tar.add(audit, "meta/" + os.path.basename(audit))
                        tar.add(content, arcname="content")
        except ArtifactExistsError:
            return ("skipped ({} exists in archive)".format(content), SKIPPED)
        except (ArtifactUploadError, tarfile.TarError, OSError) as e:
            if self.__ignoreErrors:
                return ("error ("+str(e)+")", ERROR)
            else:
                raise BuildError("Cannot upload artifact: " + str(e))
        finally:
            # Restore signals to default so that Ctrl+C kills process. Needed
            # to prevent ugly backtraces when user presses ctrl+c.
            signal.signal(signal.SIGINT, signal.SIG_DFL)
        return ("ok", EXECUTED) 

def _uploadLocalFile(self, key, suffix, content):
        # Set default signal handler so that KeyboardInterrupt is raised.
        # Needed to gracefully handle ctrl+c.
        signal.signal(signal.SIGINT, signal.default_int_handler)

        try:
            with self._openUploadFile(key, suffix) as (name, fileobj):
                writeFileOrHandle(name, fileobj, content)
        except ArtifactExistsError:
            return ("skipped (exists in archive)", SKIPPED)
        except (ArtifactUploadError, OSError) as e:
            if self.__ignoreErrors:
                return ("error ("+str(e)+")", ERROR)
            else:
                raise BuildError("Cannot upload file: " + str(e))
        finally:
            # Restore signals to default so that Ctrl+C kills process. Needed
            # to prevent ugly backtraces when user presses ctrl+c.
            signal.signal(signal.SIGINT, signal.SIG_DFL)
        return ("ok", EXECUTED) 

def __init__(self, default_handler):
        self.called = False
        self.original_handler = default_handler
        if isinstance(default_handler, int):
            if default_handler == signal.SIG_DFL:
                # Pretend it's signal.default_int_handler instead.
                default_handler = signal.default_int_handler
            elif default_handler == signal.SIG_IGN:
                # Not quite the same thing as SIG_IGN, but the closest we
                # can make it: do nothing.
                def default_handler(unused_signum, unused_frame):
                    pass
            else:
                raise TypeError("expected SIGINT signal handler to be "
                                "signal.SIG_IGN, signal.SIG_DFL, or a "
                                "callable object")
        self.default_handler = default_handler 

def __init__(self, default_handler):
        self.called = False
        self.original_handler = default_handler
        if isinstance(default_handler, (int, long)):
            if default_handler == signal.SIG_DFL:
                # Pretend it's signal.default_int_handler instead.
                default_handler = signal.default_int_handler
            elif default_handler == signal.SIG_IGN:
                # Not quite the same thing as SIG_IGN, but the closest we
                # can make it: do nothing.
                def default_handler(unused_signum, unused_frame):
                    pass
            else:
                raise TypeError("expected SIGINT signal handler to be "
                                "signal.SIG_IGN, signal.SIG_DFL, or a "
                                "callable object")
        self.default_handler = default_handler 

def test_signal_signal(self):
        WORKING_CASES = SUPPORTED_SIGNALS + [6]
        WEIRD_CASES = {
                    6: None,
                    2: signal.default_int_handler}
        for x in WORKING_CASES:
            #Ideal handler signature
            def a(signum, frame):
                return x
            
            ret_val = signal.signal(x, a)
            if x not in WEIRD_CASES.keys():
                self.assertEqual(ret_val, signal.SIG_DFL)
            else:
                self.assertEqual(ret_val, WEIRD_CASES[x])
            self.assertEqual(a, signal.getsignal(x))
            
        #Strange handler signatures
        class KNew(object):
            def __call__(self, *args, **kwargs):
                pass
        
        a = KNew()
        ret_val = signal.signal(signal.SIGBREAK, a)
        self.assertEqual(a, signal.getsignal(signal.SIGBREAK)) 

def run(self):
        """
        Run guest main thread
        """
        global virt
        global exiting
        virt = VirtioGuestPosix()
        slave = Thread(target=worker, args=(virt,))
        slave.start()
        signal.signal(signal.SIGUSR1, sigusr_handler)
        signal.signal(signal.SIGALRM, sigusr_handler)
        while not exiting:
            signal.alarm(1)
            signal.pause()
            catch = virt.catching_signal()
            if catch:
                signal.signal(signal.SIGIO, virt)
            elif catch is False:
                signal.signal(signal.SIGIO, signal.SIG_DFL)
            if catch is not None:
                virt.use_config.set()
        print("PASS: guest_exit")
        sys.exit(0) 

def __init__(self, default_handler):
        self.called = False
        self.original_handler = default_handler
        if isinstance(default_handler, int):
            if default_handler == signal.SIG_DFL:
                # Pretend it's signal.default_int_handler instead.
                default_handler = signal.default_int_handler
            elif default_handler == signal.SIG_IGN:
                # Not quite the same thing as SIG_IGN, but the closest we
                # can make it: do nothing.
                def default_handler(unused_signum, unused_frame):
                    pass
            else:
                raise TypeError("expected SIGINT signal handler to be "
                                "signal.SIG_IGN, signal.SIG_DFL, or a "
                                "callable object")
        self.default_handler = default_handler 

def permit_sigpipe():
    """Helper for subprocess.Popen(). Handle SIGPIPE. To be used as preexec_fn.

    Notes
    -----
    Things like::

        >>> cmd = r"grep pattern /path/to/very_big_file | head -n1"
        >>> pp = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE,
        ...                       stderr=subprocess.PIPE)
        >>> out,err = pp.communicate()

    sometimes end with a broken pipe error: "grep: writing output: Broken
    pipe". They run fine at the bash prompt, while failing with Popen. The
    reason is that they actually "kind of" fail in the shell too, namely,
    SIGPIPE [1,2]. This can be seen by runing the call in strace "$ strace grep
    ...". Popen chokes on that. The solution is to ignore SIGPIPE.

    References
    ----------
    .. [1] http://mail.python.org/pipermail/tutor/2007-October/058042.html
    .. [2] http://article.gmane.org/gmane.comp.python.devel/88798/
    """
    signal.signal(signal.SIGPIPE, signal.SIG_DFL)


# XXX The error handling is not safe since we raise the exception only when
# stderr is not empty w/o checking the retcode. This fails if we do
# backtick('dhwjqdhwjwqdk 2>/dev/null'). This may have been a design decision
# in order to deal with flaky shell commands. But we should never use that in
# tests. 

def _register_signal_handlers(self):
        # type: () -> None
        # SIGKILL cannot be caught or ignored, and the receiving
        # process cannot perform any clean-up upon receiving this
        # signal.
        try:
            if signal.SIGKILL in self._sigmap.keys():
                raise ValueError(
                    "Trying to set handler for SIGKILL signal. "
                    "SIGKILL cannot be cought or ignored in POSIX systems."
                )
        except AttributeError:
            pass

        for sig, sig_handler in self._sigmap.items():
            # A handler for a particular signal, once set, remains
            # installed until it is explicitly reset. Store default
            # signal handlers for subsequent reset at cleanup phase.
            dfl_handler = signal.getsignal(sig)
            self._dfl_sigmap[sig] = dfl_handler

            # ``signal.SIG_DFL`` and ``signal.SIG_IGN`` are also valid
            # signal handlers and are not callables.
            if callable(sig_handler):
                # ``signal.signal`` accepts handler function which is
                # called with two arguments: signal number and the
                # interrupted stack frame. ``functools.partial`` solves
                # the problem of passing spinner instance into the handler
                # function.
                sig_handler = functools.partial(sig_handler, spinner=self)

            signal.signal(sig, sig_handler) 

def set_blocking_signal_threshold(self, seconds, action):
        if not hasattr(signal, "setitimer"):
            gen_log.error("set_blocking_signal_threshold requires a signal module "
                          "with the setitimer method")
            return
        self._blocking_signal_threshold = seconds
        if seconds is not None:
            signal.signal(signal.SIGALRM,
                          action if action is not None else signal.SIG_DFL) 

def __doChildStart(self):
        "guts of start child process"
        self.statusPipe.postForkChild()
        _setPgid(os.getpid(), self.dag.pgid if (self.dag.pgid is not None) else os.getpid())
        cmd = self.__buildCmd()
        self.__stdioSetup(self.stdin, 0)
        self.__stdioSetup(self.stdout, 1)
        self.__stdioSetup(self.stderr, 2)
        self.__closeFiles()
        signal.signal(signal.SIGPIPE, signal.SIG_DFL)
        os.execvp(cmd[0], cmd) 

def set_blocking_signal_threshold(self, seconds, action):
        if not hasattr(signal, "setitimer"):
            gen_log.error("set_blocking_signal_threshold requires a signal module "
                          "with the setitimer method")
            return
        self._blocking_signal_threshold = seconds
        if seconds is not None:
            signal.signal(signal.SIGALRM,
                          action if action is not None else signal.SIG_DFL) 

def set_blocking_signal_threshold(self, seconds, action):
        if not hasattr(signal, "setitimer"):
            gen_log.error("set_blocking_signal_threshold requires a signal module "
                          "with the setitimer method")
            return
        self._blocking_signal_threshold = seconds
        if seconds is not None:
            signal.signal(signal.SIGALRM,
                          action if action is not None else signal.SIG_DFL) 

def __exit__(self, exc_type, exc_value, traceback):
        if not self._silent:
            if exc_type is None:
                self.update(self._total)
            self._file.write('\n')
            self._file.flush()
            if self._signal_set:
                signal.signal(signal.SIGWINCH, signal.SIG_DFL) 

def mainloop(self):
        # allow KeyboardInterrupt exceptions to close the plot window.
        signal.signal(signal.SIGINT, signal.SIG_DFL)

        QtGui.qApp.exec_()