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import os
import sys
import time
import errno
import signal
from winpty import PtyProcess
from .exceptions import ExceptionPexpect, EOF, TIMEOUT
from .spawnbase import SpawnBase
from .utils import which, split_command_line, select_ignore_interrupts
class spawn(SpawnBase):
'''This is the main class interface for Pexpect. Use this class to start
and control child applications. '''
def __init__(self, command, args=[], timeout=30, maxread=2000,
searchwindowsize=None, logfile=None, cwd=None, env=None,
encoding='utf-8', 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 = spawn('/usr/bin/ftp')
child = spawn('/usr/bin/ssh')
child = spawn('ls -latr /tmp')
You may also construct it with a list of arguments like so::
child = spawn('/usr/bin/ftp', [])
child = spawn('/usr/bin/ssh', [''])
child = 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 = spawn('/bin/bash -c "ls -l | grep LOG > logs.txt"')
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 = spawn('/bin/bash', ['-c', shell_cmd])
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 = spawn('some_command')
fout = open('mylog.txt','wb')
child.logfile = fout
Example log to stdout::
child = spawn('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 = spawn('some_command')
child.logfile_read = sys.stdout
To separately log output sent to the child use logfile_send::
child.logfile_send = fout
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 None to return to the old behavior.
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 status of the child will be stored
in self.exitstatus::
child = spawn('some_command')
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 winpty will apply.
super(spawn, self).__init__(timeout=timeout, maxread=maxread, searchwindowsize=searchwindowsize,
logfile=logfile, encoding=encoding, codec_errors=codec_errors)
self.cwd = cwd
self.env = env
if command is None:
self.command = None
self.args = None = '<pexpect factory incomplete>'
self._spawn(command, args, dimensions)
def __str__(self):
'''This returns a human-readable string that represents the state of
the object. '''
s = []
s.append('command: ' + str(self.command))
s.append('args: %r' % (self.args,))
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))
if hasattr(self, 'ptyproc'):
s.append('flag_eof: ' + str(self.flag_eof))
s.append('pid: ' + str(
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=[], dimensions=None):
'''This starts the given command in a child process. 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]
# 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, env=self.env)
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 = '<' + ' '.join(self.args) + '>'
assert is None, 'The pid member must be None.'
assert self.command is not None, 'The command member must not be None.'
kwargs = dict()
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 = self._spawnpty(self.args, env=self.env,
cwd=self.cwd, **kwargs) =
self.child_fd = self.ptyproc.fd
self.terminated = False
self.closed = False
def _spawnpty(self, args, **kwargs):
'''Spawn a pty and return an instance of PtyProcess.'''
return PtyProcess.spawn(args, **kwargs)
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 SIGINT). '''
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.'''
return self.ptyproc.isatty()
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 It uses to
implement the timeout. '''
if self.closed:
raise ValueError('I/O operation on closed file.')
if timeout == -1:
timeout = self.timeout
r, w, e = select_ignore_interrupts([self.child_fd], [], [], timeout)
if not r:
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.
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:
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
if self.delaybeforesend is not None:
s = self._coerce_send_string(s)
self._log(s, 'send')
return self.ptyproc.write(s)
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`.
s = self._coerce_send_string(s)
return self.send(s + self.linesep)
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')::
See also, sendintr() and sendeof().
n, byte = self.ptyproc.sendcontrol(char)
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()
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()
def flag_eof(self):
return self.ptyproc.flag_eof
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
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
if not self.isalive():
return True
if force:
if not self.isalive():
return True
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.
if not self.isalive():
return True
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
exitstatus = ptyproc.wait()
self.exitstatus = ptyproc.exitstatus
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 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
alive = ptyproc.isalive()
if not alive:
self.exitstatus = ptyproc.exitstatus
self.terminated = True
return alive
def kill(self, sig):
'''This sends the given signal to the child application. 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(, 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)
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