如何使用 pexpect 在 CLI 上回答命令问题？

Question

I am using Python and pexpect to automate a CLI interface for a networking device. The problem is that I cannot use pexpect to send commands that require "yes"/"no" confirmation. I think this happens because pexpect does not match the question.

child = pexpect.spawn ('ssh -p <port> user@192.168.1.1')
child.expect ("password: ")
child.sendline ('userPass')
child.expect ('> ')
child.sendline('show')
child.expect('> ')
logging.info(child.before)

# works fine untill now - it connects to the box and prints the show output

child.sendline ('reset')

logging.info(child.before)
# this command prints the same thing as previous child.before

logging.info('This line gets printed.')

child.expect ("<additional text> Are You sure? [no,yes] ")

logging.info('This line does not get printed.')

child.sendline ('yes')

Answer 1

Try this:

import re

child.expect( re.escape("<additional text> Are You sure? [no,yes] ") )

I think (but didn't check the documentation now) that pexpect handles the text as a regular expression. That is useful for matching things that aren't necessarily a constant. However, it does mean that when you want to match characters that have meaning in the regular expression grammar (eg '?', '[', and ']') then you need to escape them accordingly.

Answer 2

After escaping the expected text, the "yes" was still not accepted/sent to device. I fixed the issue by sending and additional line ('') after "yes":

child.sendline ('yes')
child.sendline('')

Answer 3

[]? are regex meta characters (they have special meaning and are not matched literally). To avoid interpreting the pattern as a regular expression, use child.expect_exact(your_pattern) instead.