如何通过交互式CLI在python中编写登录脚本

Question

I am writing a python script to log into (not ssh/telnet) a remote system (not a Linux) and run commands. Below is an example that does the things manually.

root@centos (Centos 7.3) ➜  ~ shell_tool --cmd "<cmd1>;<cmd2>" 
//interactive shell
System address: 10.0.0.1
Username: admin
Password: 123456

<output>

Besides to login and run commands, I also want to save the output. shell_tool --cmd ";" >>output.txt does not work here because there is interactive shell after the command.

Can someone help with the script?

Answer 1

We can create mockup.py that will be a stand-in for whatever program you are trying to control:

import getpass

hostname = input('System address: ')
username = input('Username: ')
password = getpass.getpass('Password: ')
if password == 'good_guess':
    while True:
        line = input('mockup> ')
        if line == 'quit':
            break

Sample Interaction

$python mockup.py
System address: bogus
Username: nobody
Password: 
mockup> fake command
mockup> quit

We can write a Python program that will control mockup.py and log all interaction to a file named session.log :

import pexpect
import getpass

hostname = input('hostname: ')
username = input('username: ')
password = getpass.getpass('password: ')
prompt = 'mockup> '

with open('session.log', 'wb') as log_file:
    session = pexpect.spawn('python3 mockup.py')
    session.expect_exact('System address: ')
    session.sendline(hostname)
    session.expect_exact('Username: ')
    session.sendline(username)
    session.expect_exact('Password: ')
    session.sendline(password)
    # Start logging to a file here
    session.logfile_read = log_file
    session.expect_exact(prompt)
    session.sendline('fake command')
    session.expect_exact(prompt)
    session.sendline('quit')
    session.expect_exact(pexpect.EOF)

Sample Interaction

$ python3 use_pexpect.py 
hostname: bogus
username: nobody
password: 

Contents of session.log

mockup> fake command
mockup> quit

This should be enough information to get you started.