A Python module for controlling interactive programs in a pseudo-terminal

There are at least two ports of pexpect to Windows APIs:

• Chris Gorecki's wexpect
• Geert Jansen's winpexpect

We could look at integrating this support into pexpect. Both Chris and Geert have said they'd be willing to help out with some initial work, but I think this would need someone committed to maintaining it and fixing the inevitable problems. I don't really use Windows myself, so I can't give it much support.

I have been using pexpect for many months with no problem. However, I recently this line:

1680 return select.select(iwtd, owtd, ewtd, timeout)

Has been creating a few problems. The select system call cannot handle more than 1024 file descriptors. On the other hand, the select.poll() system call does not have such limitations.

I understand that not all platforms support poll() but it would be nice to incorporate this system call as an option.

Up until a few weeks ago pexpect worked just fine.

My setup: A Raspberry Pi 3B+ updated with the latest Raspbain: 4.19.66-v7+ #1253 SMP Thu Aug 15 11:49:46 BST 2019 armv7l GNU/Linux

Latest python included with Raspbain: python3/oldstable,now 3.5.3-1 armhf [installed,automatic] Latest pexpect included with Raspbain: python3-pexpect/oldstable,now 4.2.1-1 all [installed]

Simplified and sanitized version of my code:

import pexpect

child = pexpect.spawn('ssh -i /home/pi/.ssh/remote_box -o StrictHostKeyChecking=no -p 22 [email protected]_box ifconfig') child.expect("remote_box': ") child.sendline('secretpassword') child.expect(pexpect.EOF, timeout=20) print (child.before)

What happens is it sends the ssh command, it then gets two identical prompt lines for the passphrase instead of just one. However pexpect never sends the secretpassword. It just times out.

Tried many things including: Tried the ssh command line outside of python. - That works fine. The prompt comes back to enter the passphrase for the key. Enter that and you get the ifconfig output and it exits from the remote box. Changed timeout=None - just hangs there forever Changed the child.expect("remote_box': ") line with shorter and longer prompt strings - no change Replaced the child.expect("remote_box': ") line entirely with time.sleep(5) - no change

What can I try next?

It would be nice if the ANSI and screen packages supported Unicode strings, or there were additional packages/classes that did. I only had to change str() to unicode() and add u in front of the quoted strings (and perhaps even some of that wasn't necessary) in screen.pretty() and put_abs() in 345eb58 to get this working quickly for me, but I didn't test all methods.

If you could suggest your preferred solution, I might be able to implement it and submit a pull request.

I am using the pexpect (version 3.1, installed via pip) on OmniOS (Solaris fork), and it works fine on the interactive shell. But when I try to use it via cron it has issues with /dev/tty. I thought this was an issue for Solaris but had been fixed? Specifically, the error is:

OSError: [Errno 6] No such device or address: '/dev/tty'

Rest of the trace:

p=pexpect.spawn('ssh -oUserKnownHostsFile=/dev/null -oStrictHostKeyChecking=no %s@%s' % ('root', host), timeout=60)
  File "/usr/lib/python2.6/site-packages/pexpect/__init__.py", line 485, in __init__
    self._spawn(command, args)
  File "/usr/lib/python2.6/site-packages/pexpect/__init__.py", line 607, in _spawn
    self.pid, self.child_fd = self.__fork_pty()
  File "/usr/lib/python2.6/site-packages/pexpect/__init__.py", line 668, in __fork_pty
    self.__pty_make_controlling_tty(child_fd)
  File "/usr/lib/python2.6/site-packages/pexpect/__init__.py", line 722, in __pty_make_controlling_tty
    fd = os.open("/dev/tty", os.O_WRONLY)
OSError: [Errno 6] No such device or address: '/dev/tty'
Traceback (most recent call last):
  File "/root/nologify.py", line 25, in <module>
    p.expect('\r\n.+]# ')
  File "/usr/lib/python2.6/site-packages/pexpect/__init__.py", line 1418, in expect
    timeout, searchwindowsize)
  File "/usr/lib/python2.6/site-packages/pexpect/__init__.py", line 1433, in expect_list
    timeout, searchwindowsize)
  File "/usr/lib/python2.6/site-packages/pexpect/__init__.py", line 1521, in expect_loop
    raise EOF(str(err) + '\n' + str(self))
pexpect.EOF: End of File (EOF). Very slow platform.
<pexpect.spawn object at 0x8181d6c>
version: 3.1
command: /usr/bin/ssh
args: ['/usr/bin/ssh', '-oUserKnownHostsFile=/dev/null', '-oStrictHostKeyChecking=no', '[email protected]']
searcher: <pexpect.searcher_re object at 0x8181dec>
buffer (last 100 chars): ''

Factor out uninterruptible select and put the code in utils as select_ignore_interrupts. Modify fdpexpect to use select_ignore_interrupts if os.name is posix. This should restore POSIX support without affecting Windows support.

Please see the commit message for details.

I'm not sure if I'm on the right track at all, so I didn't spend a huge amount of time trying to tidy the code, get the comments exactly right, etc. I'm happy to fix that stuff up if I'm on the right track. Apologies if I'm on the completely wrong track!

The screen and ANSI unit tests pass on Python 2.6, 2.7 and 3.3.

Some issues I'm aware of which I think are fairly minor:

It's not 100% clear to me which methods are meant to be public and which are only meant for internal use, so I've tried to perform decoding in all methods that accept input.

There are some cases (e.g. screen.fill(), fill_region(), put(), insert_abs(), insert()) where decoding is performed by a method that then invokes another method that also potentially performs decoding. I thought that this was safer as it meant that future refactoring wouldn't inadvertently result in decoding not being performed in some code path.

Use of the incremental decoder from ANSI.write_ch() and screen.put_abs() technically doesn't make sense, since those methods expect to receive exactly one character, and if the caller actually needs an incremental decoder to be used because they don't know where the character boundaries are in the byte stream, they shouldn't be calling those methods. However, I've just used the same incremental decoder in those methods as in all the other ones. I assume those methods probably wouldn't typically be called directly by outside code, and if they were, the user would have to have more of an idea of what they were doing with regards to multi-byte encodings.

With an incremental decoder, we're meant to call it once at the end with final=True so that any incomplete byte sequence at the end of the stream can be detected. I don't know of a sensible way to do that - perhaps screen() should have a close() method added to it that does this?

We have tried pexpect, but we have found pxssh to work better is our situation, but we are hitting a wall at one part.

I am trying to connect to multiple versions of Cisco devices. Some I have to enable, some use a '>' as a prompt and others just go to the '#' prompt. Is there a way that we can create a expect pattern with pxssh as we can with pexpect?

I would prefer to have one script running rather than having to specify which script to use with which host.

Thank you

Optimize read_nonblocking() in two ways:

1. When a lot of data is available to read, return all of it. This speeds up callers of read_nonblocking() such as expect_loop() because there are a lot less iterations in the loop.
2. Only call is_alive() if there is no data ready to read. This avoids a lot of pointless calls to is_alive().

Downstream: http://trac.sagemath.org/ticket/10295

Maybe this is just an docs issue (http://pexpect.readthedocs.org/en/stable/install.html#requirements), however pexpect >=4.0 does not work with python 2.7, because it uses a python 3.3 syntax (yield from). It is not clearly stated in docs and the install fails with a syntax error.

Installing collected packages: pexpect
  Running setup.py install for pexpect
      File "/home/smido/projects/pexeso-testing-indexer/env/lib/python2.7/site-packages/pexpect/async.py", line 16
        transport, pw = yield from asyncio.get_event_loop()\
                                 ^
    SyntaxError: invalid syntax

https://github.com/pexpect/pexpect/blob/master/pexpect/async.py#L16

File "/usr/lib/python3.4/site-packages/pexpect/init.py", line 904, in _log self.logfile.write(s) TypeError: must be str, not bytes

This contradicts the doc.

paaword.py is a script where getpass() asked the user about the password and validates it. but i want to automate the whole process and used pexpect for it (main.py). And i am using python3.10

Problem: But the problem is it not printing loop on the terminal. it running the loop in backend because its print output after sometime.

password.py

import warnings
import getpass
import time

# Suppress warnings
warnings.filterwarnings("ignore", category=getpass.GetPassWarning)
for x in range(10):
    print(f"curnt index {x}")
time.sleep(5)
password = getpass.getpass("Enter your password: ")
if password != "test":
    print("wrong password")
else:
    print("correct password")

main.py

import pexpect

child = pexpect.spawn("python password.py")

# wait for the input
child.expect("Enter your password:")

# send the password to the subprocess
child.sendline("test")

# Wait for output from the subprocess and print it
while True:
    try:
        child.expect("\n")
        print(child.before.strip())
        child.expect(pexpect.TIMEOUT, timeout=1)
    except pexpect.EOF:
        break

print(child.before.strip())

output:

Python 3.5 introduced the await and async def keywords. This change imports the coroutines from two different places, depending on the running Python version.

This address comments previously put in pull requests:

• #715
• #690

@dluyer @jdemeyer @jquast @noahsquaretrade @takluyver I'd like to get the number of open issues down to <20. Can we please discuss what we're happy with to handle issues?

I'd like to open the github discussions feature and move issues around user questions or help there so we can keep the issues only related to software problems in pexpect in the issues section. This way other users can help each other and we can keep a more clear idea about when other projects find problems or someone wishes to request features.

I don't like stale bots that auto-close because it feels like a complete lack of responsibility and ownership on problems as you can simply wait out the timer to not answer difficult questions. I am however happy to put this in if other people would prefer to have such a process.

First contribution to this project. I hope this code is of interest.

Please, let me know if there is interest on this PR and any improvement I can make to get this merged.

Thanks.

example when I use bash and input long text looks like:

[email protected]:~$ aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

use pexpect run bash and called interact then input long text looks like:

[email protected]:~$ aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

There is no line wrapping, and removing characters affects the presentation

• kubuntu 20.04
• python 3.8.10
• pexpect 4.6.0