This tests if the child process is running or not. This is
        non-blocking. If the child was terminated then this will read the
        exitstatus or signalstatus of the child. This returns True if the child
        process appears to be running or False if not. It can take literally
        SECONDS for Solaris to return the right status.

def isalive(self):
        '''This tests if the child process is running or not. This is
        non-blocking. If the child was terminated then this will read the
        exitstatus or signalstatus of the child. This returns True if the child
        process appears to be running or False if not. It can take literally
        SECONDS for Solaris to return the right status. '''

        if self.terminated:
            return False

        if self.flag_eof:
            # This is for Linux, which requires the blocking form
            # of waitpid to get the status of a defunct process.
            # This is super-lame. The flag_eof would have been set
            # in read_nonblocking(), so this should be safe.
            waitpid_options = 0
        else:
            waitpid_options = os.WNOHANG

        try:
            pid, status = os.waitpid(self.pid, waitpid_options)
        except OSError as e:
            # No child processes
            if e.errno == errno.ECHILD:
                raise PtyProcessError('isalive() encountered condition ' +
                        'where "terminated" is 0, but there was no child ' +
                        'process. Did someone else call waitpid() ' +
                        'on our process?')
            else:
                raise

        # I have to do this twice for Solaris.
        # I can't even believe that I figured this out...
        # If waitpid() returns 0 it means that no child process
        # wishes to report, and the value of status is undefined.
        if pid == 0:
            try:
                ### os.WNOHANG) # Solaris!
                pid, status = os.waitpid(self.pid, waitpid_options)
            except OSError as e:  # pragma: no cover
                # This should never happen...
                if e.errno == errno.ECHILD:
                    raise PtyProcessError('isalive() encountered condition ' +
                            'that should never happen. There was no child ' +
                            'process. Did someone else call waitpid() ' +
                            'on our process?')
                else:
                    raise

            # If pid is still 0 after two calls to waitpid() then the process
            # really is alive. This seems to work on all platforms, except for
            # Irix which seems to require a blocking call on waitpid or select,
            # so I let read_nonblocking take care of this situation
            # (unfortunately, this requires waiting through the timeout).
            if pid == 0:
                return True

        if pid == 0:
            return True

        if os.WIFEXITED(status):
            self.status = status
            self.exitstatus = os.WEXITSTATUS(status)
            self.signalstatus = None
            self.terminated = True
        elif os.WIFSIGNALED(status):
            self.status = status
            self.exitstatus = None
            self.signalstatus = os.WTERMSIG(status)
            self.terminated = True
        elif os.WIFSTOPPED(status):
            raise PtyProcessError('isalive() encountered condition ' +
                    'where child process is stopped. This is not ' +
                    'supported. Is some other process attempting ' +
                    'job control with our child pid?')
        return False