Add third_party/pexpect

third_party/pexpect/pexpect/pty_spawn.py

+import os
+import sys
+import time
+import select
+import pty
+import tty
+import errno
+import signal
+from contextlib import contextmanager
+
+import ptyprocess
+from ptyprocess.ptyprocess import use_native_pty_fork
+
+from .exceptions import ExceptionPexpect, EOF, TIMEOUT
+from .spawnbase import SpawnBase
+from .utils import which, split_command_line
+
+@contextmanager
+def _wrap_ptyprocess_err():
+    """Turn ptyprocess errors into our own ExceptionPexpect errors"""
+    try:
+        yield
+    except ptyprocess.PtyProcessError as e:
+        raise ExceptionPexpect(*e.args)
+
+PY3 = (sys.version_info[0] >= 3)
+
+class spawn(SpawnBase):
+    '''This is the main class interface for Pexpect. Use this class to start
+    and control child applications. '''
+
+    # This is purely informational now - changing it has no effect
+    use_native_pty_fork = use_native_pty_fork
+
+    def __init__(self, command, args=[], timeout=30, maxread=2000,
+                 searchwindowsize=None, logfile=None, cwd=None, env=None,
+                 ignore_sighup=False, echo=True, preexec_fn=None,
+                 encoding=None, codec_errors='strict', dimensions=None):
+        '''This is the constructor. The command parameter may be a string that
+        includes a command and any arguments to the command. For example::
+
+            child = pexpect.spawn('/usr/bin/ftp')
+            child = pexpect.spawn('/usr/bin/ssh user@example.com')
+            child = pexpect.spawn('ls -latr /tmp')
+
+        You may also construct it with a list of arguments like so::
+
+            child = pexpect.spawn('/usr/bin/ftp', [])
+            child = pexpect.spawn('/usr/bin/ssh', ['user@example.com'])
+            child = pexpect.spawn('ls', ['-latr', '/tmp'])
+
+        After this the child application will be created and will be ready to
+        talk to. For normal use, see expect() and send() and sendline().
+
+        Remember that Pexpect does NOT interpret shell meta characters such as
+        redirect, pipe, or wild cards (``>``, ``|``, or ``*``). This is a
+        common mistake.  If you want to run a command and pipe it through
+        another command then you must also start a shell. For example::
+
+            child = pexpect.spawn('/bin/bash -c "ls -l | grep LOG > logs.txt"')
+            child.expect(pexpect.EOF)
+
+        The second form of spawn (where you pass a list of arguments) is useful
+        in situations where you wish to spawn a command and pass it its own
+        argument list. This can make syntax more clear. For example, the
+        following is equivalent to the previous example::
+
+            shell_cmd = 'ls -l | grep LOG > logs.txt'
+            child = pexpect.spawn('/bin/bash', ['-c', shell_cmd])
+            child.expect(pexpect.EOF)
+
+        The maxread attribute sets the read buffer size. This is maximum number
+        of bytes that Pexpect will try to read from a TTY at one time. Setting
+        the maxread size to 1 will turn off buffering. Setting the maxread
+        value higher may help performance in cases where large amounts of
+        output are read back from the child. This feature is useful in
+        conjunction with searchwindowsize.
+
+        When the keyword argument *searchwindowsize* is None (default), the
+        full buffer is searched at each iteration of receiving incoming data.
+        The default number of bytes scanned at each iteration is very large
+        and may be reduced to collaterally reduce search cost.  After
+        :meth:`~.expect` returns, the full buffer attribute remains up to
+        size *maxread* irrespective of *searchwindowsize* value.
+
+        When the keyword argument ``timeout`` is specified as a number,
+        (default: *30*), then :class:`TIMEOUT` will be raised after the value
+        specified has elapsed, in seconds, for any of the :meth:`~.expect`
+        family of method calls.  When None, TIMEOUT will not be raised, and
+        :meth:`~.expect` may block indefinitely until match.
+
+
+        The logfile member turns on or off logging. All input and output will
+        be copied to the given file object. Set logfile to None to stop
+        logging. This is the default. Set logfile to sys.stdout to echo
+        everything to standard output. The logfile is flushed after each write.
+
+        Example log input and output to a file::
+
+            child = pexpect.spawn('some_command')
+            fout = open('mylog.txt','wb')
+            child.logfile = fout
+
+        Example log to stdout::
+
+            # In Python 2:
+            child = pexpect.spawn('some_command')
+            child.logfile = sys.stdout
+
+            # In Python 3, spawnu should be used to give str to stdout:
+            child = pexpect.spawnu('some_command')
+            child.logfile = sys.stdout
+
+        The logfile_read and logfile_send members can be used to separately log
+        the input from the child and output sent to the child. Sometimes you
+        don't want to see everything you write to the child. You only want to
+        log what the child sends back. For example::
+
+            child = pexpect.spawn('some_command')
+            child.logfile_read = sys.stdout
+
+        You will need to pass an encoding to spawn in the above code if you are
+        using Python 3.
+
+        To separately log output sent to the child use logfile_send::
+
+            child.logfile_send = fout
+
+        If ``ignore_sighup`` is True, the child process will ignore SIGHUP
+        signals. The default is False from Pexpect 4.0, meaning that SIGHUP
+        will be handled normally by the child.
+
+        The delaybeforesend helps overcome a weird behavior that many users
+        were experiencing. The typical problem was that a user would expect() a
+        "Password:" prompt and then immediately call sendline() to send the
+        password. The user would then see that their password was echoed back
+        to them. Passwords don't normally echo. The problem is caused by the
+        fact that most applications print out the "Password" prompt and then
+        turn off stdin echo, but if you send your password before the
+        application turned off echo, then you get your password echoed.
+        Normally this wouldn't be a problem when interacting with a human at a
+        real keyboard. If you introduce a slight delay just before writing then
+        this seems to clear up the problem. This was such a common problem for
+        many users that I decided that the default pexpect behavior should be
+        to sleep just before writing to the child application. 1/20th of a
+        second (50 ms) seems to be enough to clear up the problem. You can set
+        delaybeforesend to 0 to return to the old behavior. Most Linux machines
+        don't like this to be below 0.03. I don't know why.
+
+        Note that spawn is clever about finding commands on your path.
+        It uses the same logic that "which" uses to find executables.
+
+        If you wish to get the exit status of the child you must call the
+        close() method. The exit or signal status of the child will be stored
+        in self.exitstatus or self.signalstatus. If the child exited normally
+        then exitstatus will store the exit return code and signalstatus will
+        be None. If the child was terminated abnormally with a signal then
+        signalstatus will store the signal value and exitstatus will be None.
+        If you need more detail you can also read the self.status member which
+        stores the status returned by os.waitpid. You can interpret this using
+        os.WIFEXITED/os.WEXITSTATUS or os.WIFSIGNALED/os.TERMSIG.
+
+        The echo attribute may be set to False to disable echoing of input.
+        As a pseudo-terminal, all input echoed by the "keyboard" (send()
+        or sendline()) will be repeated to output.  For many cases, it is
+        not desirable to have echo enabled, and it may be later disabled
+        using setecho(False) followed by waitnoecho().  However, for some
+        platforms such as Solaris, this is not possible, and should be
+        disabled immediately on spawn.
+        
+        If preexec_fn is given, it will be called in the child process before
+        launching the given command. This is useful to e.g. reset inherited
+        signal handlers.
+
+        The dimensions attribute specifies the size of the pseudo-terminal as
+        seen by the subprocess, and is specified as a two-entry tuple (rows,
+        columns). If this is unspecified, the defaults in ptyprocess will apply.
+        '''
+        super(spawn, self).__init__(timeout=timeout, maxread=maxread, searchwindowsize=searchwindowsize,
+                                    logfile=logfile, encoding=encoding, codec_errors=codec_errors)
+        self.STDIN_FILENO = pty.STDIN_FILENO
+        self.STDOUT_FILENO = pty.STDOUT_FILENO
+        self.STDERR_FILENO = pty.STDERR_FILENO
+        self.cwd = cwd
+        self.env = env
+        self.echo = echo
+        self.ignore_sighup = ignore_sighup
+        self.__irix_hack = sys.platform.lower().startswith('irix')
+        if command is None:
+            self.command = None
+            self.args = None
+            self.name = '<pexpect factory incomplete>'
+        else:
+            self._spawn(command, args, preexec_fn, dimensions)
+
+    def __str__(self):
+        '''This returns a human-readable string that represents the state of
+        the object. '''
+
+        s = []
+        s.append(repr(self))
+        s.append('command: ' + str(self.command))
+        s.append('args: %r' % (self.args,))
+        s.append('searcher: %r' % (self.searcher,))
+        s.append('buffer (last 100 chars): %r' % (
+                self.buffer[-100:] if self.buffer else self.buffer,))
+        s.append('before (last 100 chars): %r' % (
+                self.before[-100:] if self.before else self.before,))
+        s.append('after: %r' % (self.after,))
+        s.append('match: %r' % (self.match,))
+        s.append('match_index: ' + str(self.match_index))
+        s.append('exitstatus: ' + str(self.exitstatus))
+        s.append('flag_eof: ' + str(self.flag_eof))
+        s.append('pid: ' + str(self.pid))
+        s.append('child_fd: ' + str(self.child_fd))
+        s.append('closed: ' + str(self.closed))
+        s.append('timeout: ' + str(self.timeout))
+        s.append('delimiter: ' + str(self.delimiter))
+        s.append('logfile: ' + str(self.logfile))
+        s.append('logfile_read: ' + str(self.logfile_read))
+        s.append('logfile_send: ' + str(self.logfile_send))
+        s.append('maxread: ' + str(self.maxread))
+        s.append('ignorecase: ' + str(self.ignorecase))
+        s.append('searchwindowsize: ' + str(self.searchwindowsize))
+        s.append('delaybeforesend: ' + str(self.delaybeforesend))
+        s.append('delayafterclose: ' + str(self.delayafterclose))
+        s.append('delayafterterminate: ' + str(self.delayafterterminate))
+        return '\n'.join(s)
+
+    def _spawn(self, command, args=[], preexec_fn=None, dimensions=None):
+        '''This starts the given command in a child process. This does all the
+        fork/exec type of stuff for a pty. This is called by __init__. If args
+        is empty then command will be parsed (split on spaces) and args will be
+        set to parsed arguments. '''
+
+        # The pid and child_fd of this object get set by this method.
+        # Note that it is difficult for this method to fail.
+        # You cannot detect if the child process cannot start.
+        # So the only way you can tell if the child process started
+        # or not is to try to read from the file descriptor. If you get
+        # EOF immediately then it means that the child is already dead.
+        # That may not necessarily be bad because you may have spawned a child
+        # that performs some task; creates no stdout output; and then dies.
+
+        # If command is an int type then it may represent a file descriptor.
+        if isinstance(command, type(0)):
+            raise ExceptionPexpect('Command is an int type. ' +
+                    'If this is a file descriptor then maybe you want to ' +
+                    'use fdpexpect.fdspawn which takes an existing ' +
+                    'file descriptor instead of a command string.')
+
+        if not isinstance(args, type([])):
+            raise TypeError('The argument, args, must be a list.')
+
+        if args == []:
+            self.args = split_command_line(command)
+            self.command = self.args[0]
+        else:
+            # Make a shallow copy of the args list.
+            self.args = args[:]
+            self.args.insert(0, command)
+            self.command = command
+
+        command_with_path = which(self.command)
+        if command_with_path is None:
+            raise ExceptionPexpect('The command was not found or was not ' +
+                    'executable: %s.' % self.command)
+        self.command = command_with_path
+        self.args[0] = self.command
+
+        self.name = '<' + ' '.join(self.args) + '>'
+
+        assert self.pid is None, 'The pid member must be None.'
+        assert self.command is not None, 'The command member must not be None.'
+
+        kwargs = {'echo': self.echo, 'preexec_fn': preexec_fn}
+        if self.ignore_sighup:
+            def preexec_wrapper():
+                "Set SIGHUP to be ignored, then call the real preexec_fn"
+                signal.signal(signal.SIGHUP, signal.SIG_IGN)
+                if preexec_fn is not None:
+                    preexec_fn()
+            kwargs['preexec_fn'] = preexec_wrapper
+
+        if dimensions is not None:
+            kwargs['dimensions'] = dimensions
+
+        if self.encoding is not None:
+            # Encode command line using the specified encoding
+            self.args = [a if isinstance(a, bytes) else a.encode(self.encoding)
+                         for a in self.args]
+
+        self.ptyproc = ptyprocess.PtyProcess.spawn(self.args, env=self.env,
+                                                   cwd=self.cwd, **kwargs)
+
+        self.pid = self.ptyproc.pid
+        self.child_fd = self.ptyproc.fd
+
+
+        self.terminated = False
+        self.closed = False
+
+    def close(self, force=True):
+        '''This closes the connection with the child application. Note that
+        calling close() more than once is valid. This emulates standard Python
+        behavior with files. Set force to True if you want to make sure that
+        the child is terminated (SIGKILL is sent if the child ignores SIGHUP
+        and SIGINT). '''
+
+        self.flush()
+        self.ptyproc.close(force=force)
+        self.isalive()  # Update exit status from ptyproc
+        self.child_fd = -1
+
+    def isatty(self):
+        '''This returns True if the file descriptor is open and connected to a
+        tty(-like) device, else False.
+
+        On SVR4-style platforms implementing streams, such as SunOS and HP-UX,
+        the child pty may not appear as a terminal device.  This means
+        methods such as setecho(), setwinsize(), getwinsize() may raise an
+        IOError. '''
+
+        return os.isatty(self.child_fd)
+
+    def waitnoecho(self, timeout=-1):
+        '''This waits until the terminal ECHO flag is set False. This returns
+        True if the echo mode is off. This returns False if the ECHO flag was
+        not set False before the timeout. This can be used to detect when the
+        child is waiting for a password. Usually a child application will turn
+        off echo mode when it is waiting for the user to enter a password. For
+        example, instead of expecting the "password:" prompt you can wait for
+        the child to set ECHO off::
+
+            p = pexpect.spawn('ssh user@example.com')
+            p.waitnoecho()
+            p.sendline(mypassword)
+
+        If timeout==-1 then this method will use the value in self.timeout.
+        If timeout==None then this method to block until ECHO flag is False.
+        '''
+
+        if timeout == -1:
+            timeout = self.timeout
+        if timeout is not None:
+            end_time = time.time() + timeout
+        while True:
+            if not self.getecho():
+                return True
+            if timeout < 0 and timeout is not None:
+                return False
+            if timeout is not None:
+                timeout = end_time - time.time()
+            time.sleep(0.1)
+
+    def getecho(self):
+        '''This returns the terminal echo mode. This returns True if echo is
+        on or False if echo is off. Child applications that are expecting you
+        to enter a password often set ECHO False. See waitnoecho().
+
+        Not supported on platforms where ``isatty()`` returns False.  '''
+        return self.ptyproc.getecho()
+
+    def setecho(self, state):
+        '''This sets the terminal echo mode on or off. Note that anything the
+        child sent before the echo will be lost, so you should be sure that
+        your input buffer is empty before you call setecho(). For example, the
+        following will work as expected::
+
+            p = pexpect.spawn('cat') # Echo is on by default.
+            p.sendline('1234') # We expect see this twice from the child...
+            p.expect(['1234']) # ... once from the tty echo...
+            p.expect(['1234']) # ... and again from cat itself.
+            p.setecho(False) # Turn off tty echo
+            p.sendline('abcd') # We will set this only once (echoed by cat).
+            p.sendline('wxyz') # We will set this only once (echoed by cat)
+            p.expect(['abcd'])
+            p.expect(['wxyz'])
+
+        The following WILL NOT WORK because the lines sent before the setecho
+        will be lost::
+
+            p = pexpect.spawn('cat')
+            p.sendline('1234')
+            p.setecho(False) # Turn off tty echo
+            p.sendline('abcd') # We will set this only once (echoed by cat).
+            p.sendline('wxyz') # We will set this only once (echoed by cat)
+            p.expect(['1234'])
+            p.expect(['1234'])
+            p.expect(['abcd'])
+            p.expect(['wxyz'])
+
+
+        Not supported on platforms where ``isatty()`` returns False.
+        '''
+        return self.ptyproc.setecho(state)
+
+        self.echo = state
+
+    def read_nonblocking(self, size=1, timeout=-1):
+        '''This reads at most size characters from the child application. It
+        includes a timeout. If the read does not complete within the timeout
+        period then a TIMEOUT exception is raised. If the end of file is read
+        then an EOF exception will be raised.  If a logfile is specified, a
+        copy is written to that log.
+
+        If timeout is None then the read may block indefinitely.
+        If timeout is -1 then the self.timeout value is used. If timeout is 0
+        then the child is polled and if there is no data immediately ready
+        then this will raise a TIMEOUT exception.
+
+        The timeout refers only to the amount of time to read at least one
+        character. This is not affected by the 'size' parameter, so if you call
+        read_nonblocking(size=100, timeout=30) and only one character is
+        available right away then one character will be returned immediately.
+        It will not wait for 30 seconds for another 99 characters to come in.
+
+        This is a wrapper around os.read(). It uses select.select() to
+        implement the timeout. '''
+
+        if self.closed:
+            raise ValueError('I/O operation on closed file.')
+
+        if timeout == -1:
+            timeout = self.timeout
+
+        # Note that some systems such as Solaris do not give an EOF when
+        # the child dies. In fact, you can still try to read
+        # from the child_fd -- it will block forever or until TIMEOUT.
+        # For this case, I test isalive() before doing any reading.
+        # If isalive() is false, then I pretend that this is the same as EOF.
+        if not self.isalive():
+            # timeout of 0 means "poll"
+            r, w, e = self.__select([self.child_fd], [], [], 0)
+            if not r:
+                self.flag_eof = True
+                raise EOF('End Of File (EOF). Braindead platform.')
+        elif self.__irix_hack:
+            # Irix takes a long time before it realizes a child was terminated.
+            # FIXME So does this mean Irix systems are forced to always have
+            # FIXME a 2 second delay when calling read_nonblocking? That sucks.
+            r, w, e = self.__select([self.child_fd], [], [], 2)
+            if not r and not self.isalive():
+                self.flag_eof = True
+                raise EOF('End Of File (EOF). Slow platform.')
+
+        r, w, e = self.__select([self.child_fd], [], [], timeout)
+
+        if not r:
+            if not self.isalive():
+                # Some platforms, such as Irix, will claim that their
+                # processes are alive; timeout on the select; and
+                # then finally admit that they are not alive.
+                self.flag_eof = True
+                raise EOF('End of File (EOF). Very slow platform.')
+            else:
+                raise TIMEOUT('Timeout exceeded.')
+
+        if self.child_fd in r:
+            return super(spawn, self).read_nonblocking(size)
+
+        raise ExceptionPexpect('Reached an unexpected state.')  # pragma: no cover
+
+    def write(self, s):
+        '''This is similar to send() except that there is no return value.
+        '''
+
+        self.send(s)
+
+    def writelines(self, sequence):
+        '''This calls write() for each element in the sequence. The sequence
+        can be any iterable object producing strings, typically a list of
+        strings. This does not add line separators. There is no return value.
+        '''
+
+        for s in sequence:
+            self.write(s)
+
+    def send(self, s):
+        '''Sends string ``s`` to the child process, returning the number of
+        bytes written. If a logfile is specified, a copy is written to that
+        log.
+
+        The default terminal input mode is canonical processing unless set
+        otherwise by the child process. This allows backspace and other line
+        processing to be performed prior to transmitting to the receiving
+        program. As this is buffered, there is a limited size of such buffer.
+
+        On Linux systems, this is 4096 (defined by N_TTY_BUF_SIZE). All
+        other systems honor the POSIX.1 definition PC_MAX_CANON -- 1024
+        on OSX, 256 on OpenSolaris, and 1920 on FreeBSD.
+
+        This value may be discovered using fpathconf(3)::
+
+            >>> from os import fpathconf
+            >>> print(fpathconf(0, 'PC_MAX_CANON'))
+            256
+
+        On such a system, only 256 bytes may be received per line. Any
+        subsequent bytes received will be discarded. BEL (``'\a'``) is then
+        sent to output if IMAXBEL (termios.h) is set by the tty driver.
+        This is usually enabled by default.  Linux does not honor this as
+        an option -- it behaves as though it is always set on.
+
+        Canonical input processing may be disabled altogether by executing
+        a shell, then stty(1), before executing the final program::
+
+            >>> bash = pexpect.spawn('/bin/bash', echo=False)
+            >>> bash.sendline('stty -icanon')
+            >>> bash.sendline('base64')
+            >>> bash.sendline('x' * 5000)
+        '''
+
+        time.sleep(self.delaybeforesend)
+
+        s = self._coerce_send_string(s)
+        self._log(s, 'send')
+
+        b = self._encoder.encode(s, final=False)
+        return os.write(self.child_fd, b)
+
+    def sendline(self, s=''):
+        '''Wraps send(), sending string ``s`` to child process, with
+        ``os.linesep`` automatically appended. Returns number of bytes
+        written.  Only a limited number of bytes may be sent for each
+        line in the default terminal mode, see docstring of :meth:`send`.
+        '''
+
+        n = self.send(s)
+        n = n + self.send(self.linesep)
+        return n
+
+    def _log_control(self, s):
+        """Write control characters to the appropriate log files"""
+        if self.encoding is not None:
+            s = s.decode(self.encoding, 'replace')
+        self._log(s, 'send')
+
+    def sendcontrol(self, char):
+        '''Helper method that wraps send() with mnemonic access for sending control
+        character to the child (such as Ctrl-C or Ctrl-D).  For example, to send
+        Ctrl-G (ASCII 7, bell, '\a')::
+
+            child.sendcontrol('g')
+
+        See also, sendintr() and sendeof().
+        '''
+        n, byte = self.ptyproc.sendcontrol(char)
+        self._log_control(byte)
+        return n
+
+    def sendeof(self):
+        '''This sends an EOF to the child. This sends a character which causes
+        the pending parent output buffer to be sent to the waiting child
+        program without waiting for end-of-line. If it is the first character
+        of the line, the read() in the user program returns 0, which signifies
+        end-of-file. This means to work as expected a sendeof() has to be
+        called at the beginning of a line. This method does not send a newline.
+        It is the responsibility of the caller to ensure the eof is sent at the
+        beginning of a line. '''
+
+        n, byte = self.ptyproc.sendeof()
+        self._log_control(byte)
+
+    def sendintr(self):
+        '''This sends a SIGINT to the child. It does not require
+        the SIGINT to be the first character on a line. '''
+
+        n, byte = self.ptyproc.sendintr()
+        self._log_control(byte)
+
+    @property
+    def flag_eof(self):
+        return self.ptyproc.flag_eof
+
+    @flag_eof.setter
+    def flag_eof(self, value):
+        self.ptyproc.flag_eof = value
+
+    def eof(self):
+        '''This returns True if the EOF exception was ever raised.
+        '''
+        return self.flag_eof
+
+    def terminate(self, force=False):
+        '''This forces a child process to terminate. It starts nicely with
+        SIGHUP and SIGINT. If "force" is True then moves onto SIGKILL. This
+        returns True if the child was terminated. This returns False if the
+        child could not be terminated. '''
+
+        if not self.isalive():
+            return True
+        try:
+            self.kill(signal.SIGHUP)
+            time.sleep(self.delayafterterminate)
+            if not self.isalive():
+                return True
+            self.kill(signal.SIGCONT)
+            time.sleep(self.delayafterterminate)
+            if not self.isalive():
+                return True
+            self.kill(signal.SIGINT)
+            time.sleep(self.delayafterterminate)
+            if not self.isalive():
+                return True
+            if force:
+                self.kill(signal.SIGKILL)
+                time.sleep(self.delayafterterminate)
+                if not self.isalive():
+                    return True
+                else:
+                    return False
+            return False
+        except OSError:
+            # I think there are kernel timing issues that sometimes cause
+            # this to happen. I think isalive() reports True, but the
+            # process is dead to the kernel.
+            # Make one last attempt to see if the kernel is up to date.
+            time.sleep(self.delayafterterminate)
+            if not self.isalive():
+                return True
+            else:
+                return False
+
+    def wait(self):
+        '''This waits until the child exits. This is a blocking call. This will
+        not read any data from the child, so this will block forever if the
+        child has unread output and has terminated. In other words, the child
+        may have printed output then called exit(), but, the child is
+        technically still alive until its output is read by the parent.
+
+        This method is non-blocking if :meth:`wait` has already been called
+        previously or :meth:`isalive` method returns False.  It simply returns
+        the previously determined exit status.
+        '''
+
+        ptyproc = self.ptyproc
+        with _wrap_ptyprocess_err():
+            # exception may occur if "Is some other process attempting
+            # "job control with our child pid?"
+            exitstatus = ptyproc.wait()
+        self.status = ptyproc.status
+        self.exitstatus = ptyproc.exitstatus
+        self.signalstatus = ptyproc.signalstatus
+        self.terminated = True
+
+        return exitstatus
+
+    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. '''
+
+        ptyproc = self.ptyproc
+        with _wrap_ptyprocess_err():
+            alive = ptyproc.isalive()
+
+        if not alive:
+            self.status = ptyproc.status
+            self.exitstatus = ptyproc.exitstatus
+            self.signalstatus = ptyproc.signalstatus
+            self.terminated = True
+
+        return alive
+
+    def kill(self, sig):
+
+        '''This sends the given signal to the child application. In keeping
+        with UNIX tradition it has a misleading name. It does not necessarily
+        kill the child unless you send the right signal. '''
+
+        # Same as os.kill, but the pid is given for you.
+        if self.isalive():
+            os.kill(self.pid, sig)
+
+    def getwinsize(self):
+        '''This returns the terminal window size of the child tty. The return
+        value is a tuple of (rows, cols). '''
+        return self.ptyproc.getwinsize()
+
+    def setwinsize(self, rows, cols):
+        '''This sets the terminal window size of the child tty. This will cause
+        a SIGWINCH signal to be sent to the child. This does not change the
+        physical window size. It changes the size reported to TTY-aware
+        applications like vi or curses -- applications that respond to the
+        SIGWINCH signal. '''
+        return self.ptyproc.setwinsize(rows, cols)
+
+
+    def interact(self, escape_character=chr(29),
+            input_filter=None, output_filter=None):
+
+        '''This gives control of the child process to the interactive user (the
+        human at the keyboard). Keystrokes are sent to the child process, and
+        the stdout and stderr output of the child process is printed. This
+        simply echos the child stdout and child stderr to the real stdout and
+        it echos the real stdin to the child stdin. When the user types the
+        escape_character this method will return None. The escape_character
+        will not be transmitted.  The default for escape_character is
+        entered as ``Ctrl - ]``, the very same as BSD telnet. To prevent
+        escaping, escape_character may be set to None.
+
+        If a logfile is specified, then the data sent and received from the
+        child process in interact mode is duplicated to the given log.
+
+        You may pass in optional input and output filter functions. These
+        functions should take a string and return a string. The output_filter
+        will be passed all the output from the child process. The input_filter
+        will be passed all the keyboard input from the user. The input_filter
+        is run BEFORE the check for the escape_character.
+
+        Note that if you change the window size of the parent the SIGWINCH
+        signal will not be passed through to the child. If you want the child
+        window size to change when the parent's window size changes then do
+        something like the following example::
+
+            import pexpect, struct, fcntl, termios, signal, sys
+            def sigwinch_passthrough (sig, data):
+                s = struct.pack("HHHH", 0, 0, 0, 0)
+                a = struct.unpack('hhhh', fcntl.ioctl(sys.stdout.fileno(),
+                    termios.TIOCGWINSZ , s))
+                global p
+                p.setwinsize(a[0],a[1])
+            # Note this 'p' global and used in sigwinch_passthrough.
+            p = pexpect.spawn('/bin/bash')
+            signal.signal(signal.SIGWINCH, sigwinch_passthrough)
+            p.interact()
+        '''
+
+        # Flush the buffer.
+        self.write_to_stdout(self.buffer)
+        self.stdout.flush()
+        self.buffer = self.string_type()
+        mode = tty.tcgetattr(self.STDIN_FILENO)
+        tty.setraw(self.STDIN_FILENO)
+        if escape_character is not None and PY3:
+            escape_character = escape_character.encode('latin-1')
+        try:
+            self.__interact_copy(escape_character, input_filter, output_filter)
+        finally:
+            tty.tcsetattr(self.STDIN_FILENO, tty.TCSAFLUSH, mode)
+
+    def __interact_writen(self, fd, data):
+        '''This is used by the interact() method.
+        '''
+
+        while data != b'' and self.isalive():
+            n = os.write(fd, data)
+            data = data[n:]
+
+    def __interact_read(self, fd):
+        '''This is used by the interact() method.
+        '''
+
+        return os.read(fd, 1000)
+
+    def __interact_copy(self, escape_character=None,
+            input_filter=None, output_filter=None):
+
+        '''This is used by the interact() method.
+        '''
+
+        while self.isalive():
+            r, w, e = self.__select([self.child_fd, self.STDIN_FILENO], [], [])
+            if self.child_fd in r:
+                try:
+                    data = self.__interact_read(self.child_fd)
+                except OSError as err:
+                    if err.args[0] == errno.EIO:
+                        # Linux-style EOF
+                        break
+                    raise
+                if data == b'':
+                    # BSD-style EOF
+                    break
+                if output_filter:
+                    data = output_filter(data)
+                self._log(data, 'read')
+                os.write(self.STDOUT_FILENO, data)
+            if self.STDIN_FILENO in r:
+                data = self.__interact_read(self.STDIN_FILENO)
+                if input_filter:
+                    data = input_filter(data)
+                i = -1
+                if escape_character is not None:
+                    i = data.rfind(escape_character)
+                if i != -1:
+                    data = data[:i]
+                    if data:
+                        self._log(data, 'send')
+                    self.__interact_writen(self.child_fd, data)
+                    break
+                self._log(data, 'send')
+                self.__interact_writen(self.child_fd, data)
+
+    def __select(self, iwtd, owtd, ewtd, timeout=None):
+
+        '''This is a wrapper around select.select() that ignores signals. If
+        select.select raises a select.error exception and errno is an EINTR
+        error then it is ignored. Mainly this is used to ignore sigwinch
+        (terminal resize). '''
+
+        # if select() is interrupted by a signal (errno==EINTR) then
+        # we loop back and enter the select() again.
+        if timeout is not None:
+            end_time = time.time() + timeout
+        while True:
+            try:
+                return select.select(iwtd, owtd, ewtd, timeout)
+            except select.error:
+                err = sys.exc_info()[1]
+                if err.args[0] == errno.EINTR:
+                    # if we loop back we have to subtract the
+                    # amount of time we already waited.
+                    if timeout is not None:
+                        timeout = end_time - time.time()
+                        if timeout < 0:
+                            return([], [], [])
+                else:
+                    # something else caused the select.error, so
+                    # this actually is an exception.
+                    raise
+
+def spawnu(*args, **kwargs):
+    """Deprecated: pass encoding to spawn() instead."""
+    kwargs.setdefault('encoding', 'utf-8')
+    return spawn(*args, **kwargs)