Simplest way to run an Expect script from Python

Question

I'm trying to instruct my Python installation to execute an Expect script "myexpect.sh":

#!/usr/bin/expect
spawn ssh usr@myip
expect "password:"
send "mypassword\n";
send "./mycommand1\r"
send "./mycommand2\r"
interact

I'm on Windows so re-writing the lines in the Expect script into Python are not an option. Any suggestions? Is there anything that can run it the way "./myexpect.sh" does from a bash shell?

I have had some success with the subprocess command:

subprocess.call("myexpect.sh",  shell=True)

I receive the error:

myexpect.sh is not a valid Win32 application.

How do I get around this?

...are you asking how to run a bash script on Windows without bash? I don't even see where Python comes in here. Furthermore, you probably should give .txt extensions to your shell scripts (.sh if anything) — Mateusz Kowalczyk
– Mateusz Kowalczyk, Commented Jun 22, 2012 at 16:43
@MateuszKowalczyk in a sense yes: I would like to automate running this script, from a .py file - when I run the .py file, the expect script will be called and run as part of the sequence of the .py file. — gortron
– gortron, Commented Jun 22, 2012 at 16:53
So it looks like you're not looking for a python-related solution at all (other than the fact that it's being controlled from Python). You simply want a program on Windows that will be able to read the expect script and execute it, right? — Eric Finn
– Eric Finn, Commented Jun 22, 2012 at 17:20
@EricFinn I am looking for a python solution - the myexpect.sh runs fine if I execute it from a cygwin terminal, but that is not my final goal. What I would like to do is have my python script execute my .sh script whenever I run my .py file, so I don't have to execute it from a terminal by hand before I run my .py file. — gortron
– gortron, Commented Jun 22, 2012 at 17:29
@gortron But it looks like your question isn't really Python-specific; you're just telling the OS to run a file as a program, and a solution that will allow the OS to run said file (most likely through a Windows port of Expect) would work with any language, not just Python. Or would also reading in the script and interpreting it yourself in Python be acceptable? — Eric Finn
– Eric Finn, Commented Jun 22, 2012 at 17:36

Peter Mortensen · Accepted Answer · 2018-06-03 16:40:36Z

26

Use the pexpect library. This is the Python version for Expect functionality.

Example:

child = pexpect.spawn('Some command that requires password')
child.expect('Enter password:')
child.sendline('password')
child.expect(pexpect.EOF, timeout=None)
cmd_show_data = child.before
cmd_output = cmd_show_data.split('\r\n')
for data in cmd_output:
    print data

Pexpect comes with lots of examples to learn from. For use of interact(), check out script.py from examples:

https://github.com/pexpect/pexpect/tree/master/examples

(For Windows, there is an alternative to pexpect.)

Can I use Expect on Windows without installing Cygwin?

edited Jun 3, 2018 at 16:40

Peter Mortensen

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answered Jun 22, 2012 at 16:41

pyfunc

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7 Comments

gortron Over a year ago

pexpect is a brilliant solution if you're on a Linux platform, but there is no pexpect library available for Windows platforms.

pyfunc Over a year ago

@gortron: There was an SO discussion on pexpect equivalent for windows. I have added that to the answer. See if that helps.

gortron Over a year ago

For posterity: winpexpect is a clean solution.

pyfunc Over a year ago

@gortron: Thanks! It has been long since I have been on windows platform.

jfs Over a year ago

@gortron: there is no ssh command on Windows. I don't see how using winpexpect would help here.

|

Peter Mortensen · Accepted Answer · 2018-06-03 16:43:21Z

0

Since it is an .expect script, I think you should change the extend name of your script.

Instead of using

subprocess.call("myexpect.sh", shell=True)

you should use

subprocess.call("myexpect.expect", shell=True)

edited Jun 3, 2018 at 16:43

Peter Mortensen

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answered Feb 28, 2018 at 20:17

MaxGu

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2 Comments

Cipher Over a year ago

It's fine, bro. Since there is a shebang, it doesn't matter whatever the file extension is.

uchuugaka Over a year ago

The system should not care but it is good to be explicit when possible.

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