后台进程挂起（tty 输出）

Question

I've a python script which calls a bash script to connect a vpn account. If I run python script from console, I can do 2FA and connect to my VPN account seamlessly. However, if I run this python script as a background process (with nohup , etc.) then the python process becomes suspended ( + suspended (tty output) ) whenever I try to connect VPN and python program is not responding (looks like it is stuck in a state that expects an input).

vpn_manager.py :

connection_command = 'sh {}'.format(os.path.join(base_path, 'scripts', 'vpn.sh'))

response = subprocess.run(connection_command, shell=True, stdout=subprocess.PIPE)
stdout = response.stdout.decode('utf-8')

if 'state: Connected' in stdout:
    update_icon(environment)

Shell script vpn.sh :

printf "1\nUSERNAME\nPASSWORD\n2\n" | /opt/cisco/anyconnect/bin/vpn -s connect VPN_HOST

Normally, this VPN command asks for a user name and password, then waits for me to verify it from my 2FA app on my phone.

How can I make this python code working as a background process and not interrupted with that VPN prompts?

Answer 1

Using pexpect is a better approach to communicate as @CharlesDuffy suggested.

Solution with pexpect will be similar to below example.

import pexpect

failed = False
vpn = pexpect.spawn('/opt/cisco/anyconnect/bin/vpn -s connect {}'.format(host))
ret = vpn.expect([pexpect.TIMEOUT, CONNECT_SUCCESS, CONNECT_ERR_1, CONNECT_ERR_2, ...])
if ret != 1:
    failed = True

if not failed:
    vpn.sendline('1')
    ret = vpn.expect([pexpect.TIMEOUT, SELECT_GROUP_SUCCESS, SELECT_GROUP_ERR_1, SELECT_GROUP_ERR_2, ...])
    if ret != 1:
        failed = True

if not failed:
    vpn.sendline(USER_NAME)
    ret = vpn.expect([pexpect.TIMEOUT, USER_NAME_SUCCESS, USER_NAME_ERR_1, USER_NAME_ERR_2, ...])
    if ret != 1:
        failed = True

if not failed:
    vpn.sendline(PASSWORD)
    ret = vpn.expect([pexpect.TIMEOUT, PASSWORD_SUCCESS, PASSWORD_ERR_1, PASSWORD_ERR_2, ...])
    if ret != 1:
        failed = True

if not failed:
    vpn.sendline(AUTHENTICATION_METHOD)
    ret = vpn.expect([pexpect.TIMEOUT, AUTHENTICATION_SUCCESS, AUTHENTICATION_ERR_1, AUTHENTICATION_ERR_2, ...])
    if ret != 1:
        failed = True

if not failed:
    print('Connected!')
else:
    print('Failed to connect!')

Answer 2

Send the output to a file (or named pipe)

printf "1\nUSERNAME\nPASSWORD\n2\n" | /opt/cisco/anyconnect/bin/vpn -s connect VPN_HOST > /tmp/vpn.out

Then in you python script you can check that file content until you read the expected content.