Read remote output and respond using paramiko (SSH.execute)

Question

I am using the python paramiko module to run a built in parmiko function SSH.execute on a remote server. I want to run a script on the server which will require 4 prompts. I was planning to do a more complex version of this:

   ExpectedString = 'ExpectedOutput'
   Output = SSH.execute('./runScript')
   if Output == ExpectedString:
       SSH.execute('Enter this')
   else:
       raise SomeException

The problem is nothing comes back for output as the server was waiting for a number to entered and the script gets stuck at this SSH.execute command. So even if another SSH.execute command is run after it never gets run! Should I be looking to use something other than paramiko?

leoluk · Accepted Answer · 2012-10-08 15:53:20Z

3

You need to interact with the remote script. Actually, SSH.execute doesn't exist, I assume you're talking about exec_command. Instead of just returning the output, it actually gives you wrappers for stdout, stdin and stderr streams. You can directly use these in order to communicate with the remote script.

Basically, this is how you run a command and pass data over stdin (and receive output using stdout):

ssh.connect('127.0.0.1', username='foo', password='bar')

stdin, stdout, stderr = ssh.exec_command("some_script")

stdin.write('expected_input\n')
stdin.flush()

data = stdout.read.splitlines()

You should check for the prompts, of course, instead of relying on good timing.

edited Oct 8, 2012 at 15:53

answered Oct 8, 2012 at 15:40

leoluk

13k6 gold badges47 silver badges51 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Sarah92 Over a year ago

Thanks for your answer! Would you mind explaining the process behind what the meaning of using stdin.write,stdin.flush and data is for ?

leoluk Over a year ago

in short: your application receives data using stdin and outputs data using stdout (and stderr for errors, usually, you don't notice that there's a difference as a shell displays both). In Python, you can use them pretty much like file objects (which are actually streams as well), i.e. read, write, flush... docs.python.org/library/io.html

Sarah92 Over a year ago

this solution doesn't work for me- execution of ssh.exec_command still hangs as before waiting for an input so no output is returned to the python script.

colin0117 · Accepted Answer · 2016-05-10 09:57:31Z

0

@leoluk - yep, I understand your problem, both those recommended solutions won't work. The problem, as you said, with exec_command is that you can only read the output once the command completes. So, if you wanted to remotely run the command rm -i *, you won't be able to read which file is to be deleted before you can respond with a "yes" or a "no". The key here is to use invoke_shell. See this youtube link - https://www.youtube.com/watch?v=lLKdxIu3-A4 - this helped and got me going.

answered May 10, 2016 at 9:57

colin0117

1,5581 gold badge12 silver badges16 bronze badges

Collectives™ on Stack Overflow

Read remote output and respond using paramiko (SSH.execute)

2 Answers 2

3 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related