Implement an interactive shell over ssh in Python

问题:

I want to write a program (in Python 3.x on Windows 7) that executes multiple commands on a remote shell via ssh. After looking at paramikos' exec_command() function, i realized it's not suitable for my use case (because the channel gets closed after the command is executed), as the commands depend on environment variables (set by prior commands) and can't be concatenated into one exec_command() call as they are to be executed at different times in the program.

Thus, i want to execute commands in the same channel. The next option I looked into was implementing an interactive shell using paramikos' invoke_shell() function:

ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect(host, username=user, password=psw, port=22)

channel = ssh.invoke_shell()

out = channel.recv(9999)

channel.send('cd mivne_final\n')
channel.send('ls\n')

while not channel.recv_ready():
    time.sleep(3)

out = channel.recv(9999)
print(out.decode("ascii"))

channel.send('cd ..\n')
channel.send('cd or_fail\n')
channel.send('ls\n')

while not channel.recv_ready():
    time.sleep(3)

out = channel.recv(9999)
print(out.decode("ascii"))

channel.send('cd ..\n')
channel.send('cd simulator\n')
channel.send('ls\n')

while not channel.recv_ready():
    time.sleep(3)

out = channel.recv(9999)
print(out.decode("ascii"))

ssh.close() 

There are some problems with this code:

1. The first 'print' doesn't always print the 'ls' output (sometimes it is only printed on the second 'print').
2. The first 'cd' and 'ls' commands are always present in the output (I get them via the 'recv' command, as part of the output), while all the following 'cd' and 'ls' commands are printed sometimes, and sometimes they aren't.
3. The second and third 'cd' and 'ls' commands (when printed) always appear before the first 'ls' output.

I'm confused with this "non-determinism" and would very much appreciate your help.

回答1:

import paramiko
import re


class ShellHandler:

    def __init__(self, host, user, psw):
        self.ssh = paramiko.SSHClient()
        self.ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
        self.ssh.connect(host, username=user, password=psw, port=22)

        channel = self.ssh.invoke_shell()
        self.stdin = channel.makefile('wb')
        self.stdout = channel.makefile('r')

    def __del__(self):
        self.ssh.close()

    def execute(self, cmd):
        """

        :param cmd: the command to be executed on the remote computer
        :examples:  execute('ls')
                    execute('finger')
                    execute('cd folder_name')
        """
        cmd = cmd.strip('\n')
        self.stdin.write(cmd + '\n')
        finish = 'end of stdOUT buffer. finished with exit status'
        echo_cmd = 'echo {} $?'.format(finish)
        self.stdin.write(echo_cmd + '\n')
        shin = self.stdin
        self.stdin.flush()

        shout = []
        sherr = []
        exit_status = 0
        for line in self.stdout:
            if str(line).startswith(cmd) or str(line).startswith(echo_cmd):
                # up for now filled with shell junk from stdin
                shout = []
            elif str(line).startswith(finish):
                # our finish command ends with the exit status
                exit_status = int(str(line).rsplit(maxsplit=1)[1])
                if exit_status:
                    # stderr is combined with stdout.
                    # thus, swap sherr with shout in a case of failure.
                    sherr = shout
                    shout = []
                break
            else:
                # get rid of 'coloring and formatting' special characters
                shout.append(re.compile(r'(\x9B|\x1B\[)[0-?]*[ -/]*[@-~]').sub('', line).
                             replace('\b', '').replace('\r', ''))

        # first and last lines of shout/sherr contain a prompt
        if shout and echo_cmd in shout[-1]:
            shout.pop()
        if shout and cmd in shout[0]:
            shout.pop(0)
        if sherr and echo_cmd in sherr[-1]:
            sherr.pop()
        if sherr and cmd in sherr[0]:
            sherr.pop(0)

        return shin, shout, sherr

回答2:

I'm basically using all your code and just adding a for loop:

commands = ["ls","command2","command3"]
conn_one = ShellHandler(host,name,pwd)
for command in commands:
      conn_one.execute(command)

It executes 2 of the commands with the correct output but then it just sits there. I'm wondering if I need to call del somewhere in the code.