Implement an interactive shell over ssh in Python using Paramiko?

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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.

1 Answers
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