Develop Reference

Command output is corrupted when executed using Python Paramiko exec_command

I'm a software tester, trying to verify that the log on a remote QNX (a BSD variant) machine will contain the correct entries after specific actions are taken. I am able to list the contents of the directory in which the log resides, and use that information in the command to read (really want to use tail -n XX <file>) the file. So far, I always get a "(No such file or directory)" when trying to read the file.
We are using Froglogic Squish for automated testing, because the Windows UI (that interacts with the server piece on QNX) is built using Qt extensions for standard Windows elements. Squish uses Python 2.7, so I am using Python 2.7.
I am using paramiko for the SSH connection to the QNX server. This has worked great for sending commands to the simulator piece that also runs on the QNX server.
So, here's the code. Some descriptive names have been changed to avoid upsetting my employer.
import sys
import time
import select
sys.path.append(r"C:\Python27\Lib\site-packages")
sys.path.append(r"C:\Python27\Lib\site-packages\pip\_vendor")
import paramiko
# Import SSH configuration variables
ssh_host = 'vvv.xxx.yyy.zzz'
thelog_dir = "/logs/the/"
ssh_user = 'un'
ssh_pw = 'pw'
def execute_Command(fullCmd):
outptLines = []
#
# Try to connect to the host.
# Retry a few times if it fails.
#
i = 1
while True:
try:
ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect(ssh_host, 22, ssh_user, ssh_pw)
break
except paramiko.AuthenticationException:
log ("Authentication failed when connecting to %s" % ssh_host)
return 1
except:
log ("Could not SSH to %s, waiting for it to start" % ssh_host)
i += 1
time.sleep(2)
# If we could not connect within time limit
if i == 30:
log ("Could not connect to %s. Giving up" % ssh_host)
return 1
# Send the command (non-blocking?)
stdin, stdout, stderr = ssh.exec_command(fullCmd, get_pty=True)
for line in iter(stdout.readline, ""):
outptLines.append(line)
#
# Disconnect from the host
#
ssh.close()
return outptLines
def get_Latest_Log():
fullCmd = "ls -1 %s | grep the_2" %thelog_dir
files = execute_Command(fullCmd)
theFile = files[-1]
return theFile
def main():
numLines = 20
theLog = get_Latest_Log()
print("\n\nThe latest log is %s\n\n" %theLog)
fullCmd = "cd /logs/the; tail -n 20 /logs/the/%s" %theLog
#fullCmd = "tail -n 20 /logs/the/%s" %theLog
print fullCmd
logLines = execute_Command(fullCmd)
for line in logLines:
print line
if __name__ == "__main__":
# execute only if run as a script
main()
I have tried to read the file using both tail and cat. I have also tried to get and open the file using Paramiko's SFTP client.
In all cases, the response of trying to read the file fails -- despite the fact that listing the contents of the directory works fine. (?!) And BTW, the log file is supposed to be readable by 'world'. Permissions are -rw-rw-r--.
The output I get is:
"C:\Users\xsat086\Documents\paramikoTest>python SSH_THE_MsgChk.py
The latest log is the_20210628_115455_205.log
cd /logs/the; tail -n 20 /logs/the/the_20210628_115455_205.log
(No such file or directory)the/the_20210628_115455_205.log"
The file name is correct. If I copy and paste the tail command into an interactive SSH session with the QNX server, it works fine.
Is it something to do with the 'non-interactive' nature of this method of sending commands? I read that some implementations of SSH are built upon a command that offers a very limited environment. I don't see how that would impact this tail command.
Or am I doing something stupid in this code?

I cannot really explain completely, why you get the results you get.
But in general a corrupted output is a result of enabling and not handling terminal emulation. You enable the terminal emulation using get_pty=True. Remove it. You should not use the terminal emulation, when automating command execution.
Related question:
Is there a simple way to get rid of junk values that come when you SSH using Python's Paramiko library and fetch output from CLI of a remote machine?

How to interact with ssh using subprocess module

I'm trying to spawn an ssh child process using subprocess.
I'm working on Python 2.7.6 on Windows 7
here is my code:
from subprocess import *
r=Popen("ssh sshserver#localhost", stdout=PIPE)
stdout, stderr=r.communicate()
print(stdout)
print(stderr)
The outputs:
None
stdout should contain:
sshserver#localhost's password:

Here's an example of working SSH code that handles the promt for yes/no on the certificate part and also when asked for a password.
#!/usr/bin/python
import pty, sys
from subprocess import Popen, PIPE, STDOUT
from time import sleep
from os import fork, waitpid, execv, read, write
class ssh():
def __init__(self, host, execute='echo "done" > /root/testing.txt', askpass=False, user='root', password=b'SuperSecurePassword'):
self.exec = execute
self.host = host
self.user = user
self.password = password
self.askpass = askpass
self.run()
def run(self):
command = [
'/usr/bin/ssh',
self.user+'#'+self.host,
'-o', 'NumberOfPasswordPrompts=1',
self.exec,
]
# PID = 0 for child, and the PID of the child for the parent
pid, child_fd = pty.fork()
if not pid: # Child process
# Replace child process with our SSH process
execv(command[0], command)
## if we havn't setup pub-key authentication
## we can loop for a password promt and "insert" the password.
while self.askpass:
try:
output = read(child_fd, 1024).strip()
except:
break
lower = output.lower()
# Write the password
if b'password:' in lower:
write(child_fd, self.password + b'\n')
break
elif b'are you sure you want to continue connecting' in lower:
# Adding key to known_hosts
write(child_fd, b'yes\n')
elif b'company privacy warning' in lower:
pass # This is an understood message
else:
print('Error:',output)
waitpid(pid, 0)
The reason (and correct me if i'm wrong here) for you not being able to read the stdin straight away is because SSH runs as a subprocess under a different process ID which you need to read/attach to.
Since you're using windows, pty will not work. there's two solutions that would work better and that's pexpect and as someone pointed out key-based authentication.
In order to achieve a key-based authentication you only need to do the following:
On your client, run: ssh-keygen
Copy your id_rsa.pub content (one line) into /home/user/.ssh/authorized_keys on the server.
And you're done.
If not, go with pexpect.
import pexpect
child = pexpect.spawn('ssh user#host.com')
child.expect('Password:')
child.sendline('SuperSecretPassword')

Remote executing of program via xterm run using paramiko python ssh library

Flow of the program is:
Connect to OpenSSH server on Linux machine using Paramiko library
Open X11 session
Run xterm executable
Run some other program (e.g. Firefox) by typing executable name in the terminal and running it.
I would be grateful if someone can explain how to cause some executable to run in a terminal which was open by using the following code and provide sample source code (source):
import select
import sys
import paramiko
import Xlib.support.connect as xlib_connect
import os
import socket
import subprocess
# run xming
XmingProc = subprocess.Popen("C:/Program Files (x86)/Xming/Xming.exe :0 -clipboard -multiwindow")
ssh_client = paramiko.SSHClient()
ssh_client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh_client.connect(SSHServerIP, SSHServerPort, username=user, password=pwd)
transport = ssh_client.get_transport()
channelOppositeEdges = {}
local_x11_display = xlib_connect.get_display(os.environ['DISPLAY'])
inputSockets = []
def x11_handler(channel, (src_addr, src_port)):
local_x11_socket = xlib_connect.get_socket(*local_x11_display[:3])
inputSockets.append(local_x11_socket)
inputSockets.append(channel)
channelOppositeEdges[local_x11_socket.fileno()] = channel
channelOppositeEdges[channel.fileno()] = local_x11_socket
transport._queue_incoming_channel(channel)
session = transport.open_session()
inputSockets.append(session)
session.request_x11(handler = x11_handler)
session.exec_command('xterm')
transport.accept()
while not session.exit_status_ready():
readable, writable, exceptional = select.select(inputSockets,[],[])
if len(transport.server_accepts) > 0:
transport.accept()
for sock in readable:
if sock is session:
while session.recv_ready():
sys.stdout.write(session.recv(4096))
while session.recv_stderr_ready():
sys.stderr.write(session.recv_stderr(4096))
else:
try:
data = sock.recv(4096)
counterPartSocket = channelOppositeEdges[sock.fileno()]
counterPartSocket.sendall(data)
except socket.error:
inputSockets.remove(sock)
inputSockets.remove(counterPartSocket)
del channelOppositeEdges[sock.fileno()]
del channelOppositeEdges[counterPartSocket.fileno()]
sock.close()
counterPartSocket.close()
print 'Exit status:', session.recv_exit_status()
while session.recv_ready():
sys.stdout.write(session.recv(4096))
while session.recv_stderr_ready():
sys.stdout.write(session.recv_stderr(4096))
session.close()
XmingProc.terminate()
XmingProc.wait()
I was thinking about running the program in child thread, while the thread running the xterm is waiting for the child to terminate.

Well, this is a bit of a hack, but hey.
What you can do on the remote end is the following: Inside the xterm, you run netcat, listen to any data coming in on some port, and pipe whatever you get into bash. It's not quite the same as typing it into xterm direclty, but it's almost as good as typing it into bash directly, so I hope it'll get you a bit closer to your goal. If you really want to interact with xterm directly, you might want to read this.
For example:
terminal 1:
% nc -l 3333 | bash
terminal 2 (type echo hi here):
% nc localhost 3333
echo hi
Now you should see hi pop out of the first terminal. Now try it with xterm&. It worked for me.
Here's how you can automate this in Python. You may want to add some code that enables the server to tell the client when it's ready, rather than using the silly time.sleeps.
import select
import sys
import paramiko
import Xlib.support.connect as xlib_connect
import os
import socket
import subprocess
# for connecting to netcat running remotely
from multiprocessing import Process
import time
# data
import getpass
SSHServerPort=22
SSHServerIP = "localhost"
# get username/password interactively, or use some other method..
user = getpass.getuser()
pwd = getpass.getpass("enter pw for '" + user + "': ")
NETCAT_PORT = 3333
FIREFOX_CMD="/path/to/firefox &"
#FIREFOX_CMD="xclock&"#or this :)
def run_stuff_in_xterm():
time.sleep(5)
s = socket.socket(socket.AF_INET6 if ":" in SSHServerIP else socket.AF_INET, socket.SOCK_STREAM)
s.connect((SSHServerIP, NETCAT_PORT))
s.send("echo \"Hello there! Are you watching?\"\n")
s.send(FIREFOX_CMD + "\n")
time.sleep(30)
s.send("echo bye bye\n")
time.sleep(2)
s.close()
# run xming
XmingProc = subprocess.Popen("C:/Program Files (x86)/Xming/Xming.exe :0 -clipboard -multiwindow")
ssh_client = paramiko.SSHClient()
ssh_client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh_client.connect(SSHServerIP, SSHServerPort, username=user, password=pwd)
transport = ssh_client.get_transport()
channelOppositeEdges = {}
local_x11_display = xlib_connect.get_display(os.environ['DISPLAY'])
inputSockets = []
def x11_handler(channel, (src_addr, src_port)):
local_x11_socket = xlib_connect.get_socket(*local_x11_display[:3])
inputSockets.append(local_x11_socket)
inputSockets.append(channel)
channelOppositeEdges[local_x11_socket.fileno()] = channel
channelOppositeEdges[channel.fileno()] = local_x11_socket
transport._queue_incoming_channel(channel)
session = transport.open_session()
inputSockets.append(session)
session.request_x11(handler = x11_handler)
session.exec_command("xterm -e \"nc -l 0.0.0.0 %d | /bin/bash\"" % NETCAT_PORT)
p = Process(target=run_stuff_in_xterm)
transport.accept()
p.start()
while not session.exit_status_ready():
readable, writable, exceptional = select.select(inputSockets,[],[])
if len(transport.server_accepts) > 0:
transport.accept()
for sock in readable:
if sock is session:
while session.recv_ready():
sys.stdout.write(session.recv(4096))
while session.recv_stderr_ready():
sys.stderr.write(session.recv_stderr(4096))
else:
try:
data = sock.recv(4096)
counterPartSocket = channelOppositeEdges[sock.fileno()]
counterPartSocket.sendall(data)
except socket.error:
inputSockets.remove(sock)
inputSockets.remove(counterPartSocket)
del channelOppositeEdges[sock.fileno()]
del channelOppositeEdges[counterPartSocket.fileno()]
sock.close()
counterPartSocket.close()
p.join()
print 'Exit status:', session.recv_exit_status()
while session.recv_ready():
sys.stdout.write(session.recv(4096))
while session.recv_stderr_ready():
sys.stdout.write(session.recv_stderr(4096))
session.close()
XmingProc.terminate()
XmingProc.wait()
I tested this on a Mac, so I commented out the XmingProc bits and used /Applications/Firefox.app/Contents/MacOS/firefox as FIREFOX_CMD (and xclock).
The above isn't exactly a secure setup, as anyone connecting to the port at the right time could run arbitrary code on your remote server, but it sounds like you're planning to use this for testing purposes anyway. If you want to improve the security, you could make netcat bind to 127.0.0.1 rather than 0.0.0.0, setup an ssh tunnel (run ssh -L3333:localhost:3333 username#remote-host.com to tunnel all traffic received locally on port 3333 to remote-host.com:3333), and let Python connect to ("localhost", 3333).
Now you can combine this with selenium for browser automation:
Follow the instructions from this page, i.e. download the selenium standalone server jar file, put it into /path/to/some/place (on the server), and pip install -U selenium (again, on the server).
Next, put the following code into selenium-example.py in /path/to/some/place:
#!/usr/bin/env python
from selenium import webdriver
from selenium.common.exceptions import NoSuchElementException
from selenium.webdriver.common.keys import Keys
import time
browser = webdriver.Firefox() # Get local session of firefox
browser.get("http://www.yahoo.com") # Load page
assert "Yahoo" in browser.title
elem = browser.find_element_by_name("p") # Find the query box
elem.send_keys("seleniumhq" + Keys.RETURN)
time.sleep(0.2) # Let the page load, will be added to the API
try:
browser.find_element_by_xpath("//a[contains(#href,'http://docs.seleniumhq.org')]")
except NoSuchElementException:
assert 0, "can't find seleniumhq"
browser.close()
and change the firefox command:
FIREFOX_CMD="cd /path/to/some/place && python selenium-example.py"
And watch firefox do a Yahoo search. You might also want to increase the time.sleep.
If you want to run more programs, you can do things like this before or after running firefox:
# start up xclock, wait for some time to pass, kill it.
s.send("xclock&\n")
time.sleep(1)
s.send("XCLOCK_PID=$!\n") # stash away the process id (into a bash variable)
time.sleep(30)
s.send("echo \"killing $XCLOCK_PID\"\n")
s.send("kill $XCLOCK_PID\n\n")
time.sleep(5)
If you want to do perform general X11 application control, I think you might need to write similar "driver applications", albeit using different libraries. You might want search for "x11 send {mouse|keyboard} events" to find more general approaches. That brings up these questions, but I'm sure there's lots more.
If the remote end isn't responding instantaneously, you might want to sniff your network traffic in Wireshark, and check whether or not TCP is batching up the data, rather than sending it line by line (the \n seems to help here, but I guess there's no guarantee). If this is the case, you might be out of luck, but nothing is impossible. I hope you don't need to go that far though ;-)
One more note: if you need to communicate with CLI programs' STDIN/STDOUT, you might want to look at expect scripting (e.g. using pexpect, or for simple cases you might be able to use subprocess.Popen.communicate](http://docs.python.org/2/library/subprocess.html#subprocess.Popen.communicate)).

How to make a ssh connection with python?

Can anyone recommend something for making a ssh connection in python?
I need it to be compatible with any OS.
I've already tried pyssh only to get an error with SIGCHLD, which I've read is because Windows lacks this.
I've tried getting paramiko to work, but I've had errors between paramiko and Crypto to the point where the latest versions of each won't work together.
Python 2.6.1 currently on a Windows machine.

Notice that this doesn't work in Windows.
The module pxssh does exactly what you want:
For example, to run 'ls -l' and to print the output, you need to do something like that :
from pexpect import pxssh
s = pxssh.pxssh()
if not s.login ('localhost', 'myusername', 'mypassword'):
print "SSH session failed on login."
print str(s)
else:
print "SSH session login successful"
s.sendline ('ls -l')
s.prompt() # match the prompt
print s.before # print everything before the prompt.
s.logout()
Some links :
Pxssh docs : http://dsnra.jpl.nasa.gov/software/Python/site-packages/Contrib/pxssh.html
Pexpect (pxssh is based on pexpect) : http://pexpect.readthedocs.io/en/stable/

Twisted has SSH support : http://www.devshed.com/c/a/Python/SSH-with-Twisted/
The twisted.conch package adds SSH support to Twisted. This chapter shows how you can use the modules in twisted.conch to build SSH servers and clients.
Setting Up a Custom SSH Server
The command line is an incredibly efficient interface for certain tasks. System administrators love the ability to manage applications by typing commands without having to click through a graphical user interface. An SSH shell is even better, as it’s accessible from anywhere on the Internet.
You can use twisted.conch to create an SSH server that provides access to a custom shell with commands you define. This shell will even support some extra features like command history, so that you can scroll through the commands you’ve already typed.
How Do I Do That?
Write a subclass of twisted.conch.recvline.HistoricRecvLine that implements your shell protocol. HistoricRecvLine is similar to twisted.protocols.basic.LineReceiver , but with higher-level features for controlling the terminal.
Write a subclass of twisted.conch.recvline.HistoricRecvLine that implements your shell protocol. HistoricRecvLine is similar to twisted.protocols.basic.LineReceiver, but with higher-level features for controlling the terminal.
To make your shell available through SSH, you need to implement a few different classes that twisted.conch needs to build an SSH server. First, you need the twisted.cred authentication classes: a portal, credentials checkers, and a realm that returns avatars. Use twisted.conch.avatar.ConchUser as the base class for your avatar. Your avatar class should also implement twisted.conch.interfaces.ISession , which includes an openShell method in which you create a Protocol to manage the user’s interactive session. Finally, create a twisted.conch.ssh.factory.SSHFactory object and set its portal attribute to an instance of your portal.
Example 10-1 demonstrates a custom SSH server that authenticates users by their username and password. It gives each user a shell that provides several commands.
Example 10-1. sshserver.py
from twisted.cred import portal, checkers, credentials
from twisted.conch import error, avatar, recvline, interfaces as conchinterfaces
from twisted.conch.ssh import factory, userauth, connection, keys, session, common from twisted.conch.insults import insults from twisted.application import service, internet
from zope.interface import implements
import os
class SSHDemoProtocol(recvline.HistoricRecvLine):
def __init__(self, user):
self.user = user
def connectionMade(self) :
recvline.HistoricRecvLine.connectionMade(self)
self.terminal.write("Welcome to my test SSH server.")
self.terminal.nextLine()
self.do_help()
self.showPrompt()
def showPrompt(self):
self.terminal.write("$ ")
def getCommandFunc(self, cmd):
return getattr(self, ‘do_’ + cmd, None)
def lineReceived(self, line):
line = line.strip()
if line:
cmdAndArgs = line.split()
cmd = cmdAndArgs[0]
args = cmdAndArgs[1:]
func = self.getCommandFunc(cmd)
if func:
try:
func(*args)
except Exception, e:
self.terminal.write("Error: %s" % e)
self.terminal.nextLine()
else:
self.terminal.write("No such command.")
self.terminal.nextLine()
self.showPrompt()
def do_help(self, cmd=”):
"Get help on a command. Usage: help command"
if cmd:
func = self.getCommandFunc(cmd)
if func:
self.terminal.write(func.__doc__)
self.terminal.nextLine()
return
publicMethods = filter(
lambda funcname: funcname.startswith(‘do_’), dir(self))
commands = [cmd.replace(‘do_’, ”, 1) for cmd in publicMethods]
self.terminal.write("Commands: " + " ".join(commands))
self.terminal.nextLine()
def do_echo(self, *args):
"Echo a string. Usage: echo my line of text"
self.terminal.write(" ".join(args))
self.terminal.nextLine()
def do_whoami(self):
"Prints your user name. Usage: whoami"
self.terminal.write(self.user.username)
self.terminal.nextLine()
def do_quit(self):
"Ends your session. Usage: quit"
self.terminal.write("Thanks for playing!")
self.terminal.nextLine()
self.terminal.loseConnection()
def do_clear(self):
"Clears the screen. Usage: clear"
self.terminal.reset()
class SSHDemoAvatar(avatar.ConchUser):
implements(conchinterfaces.ISession)
def __init__(self, username):
avatar.ConchUser.__init__(self)
self.username = username
self.channelLookup.update({‘session’:session.SSHSession})
def openShell(self, protocol):
serverProtocol = insults.ServerProtocol(SSHDemoProtocol, self)
serverProtocol.makeConnection(protocol)
protocol.makeConnection(session.wrapProtocol(serverProtocol))
def getPty(self, terminal, windowSize, attrs):
return None
def execCommand(self, protocol, cmd):
raise NotImplementedError
def closed(self):
pass
class SSHDemoRealm:
implements(portal.IRealm)
def requestAvatar(self, avatarId, mind, *interfaces):
if conchinterfaces.IConchUser in interfaces:
return interfaces[0], SSHDemoAvatar(avatarId), lambda: None
else:
raise Exception, "No supported interfaces found."
def getRSAKeys():
if not (os.path.exists(‘public.key’) and os.path.exists(‘private.key’)):
# generate a RSA keypair
print "Generating RSA keypair…"
from Crypto.PublicKey import RSA
KEY_LENGTH = 1024
rsaKey = RSA.generate(KEY_LENGTH, common.entropy.get_bytes)
publicKeyString = keys.makePublicKeyString(rsaKey)
privateKeyString = keys.makePrivateKeyString(rsaKey)
# save keys for next time
file(‘public.key’, ‘w+b’).write(publicKeyString)
file(‘private.key’, ‘w+b’).write(privateKeyString)
print "done."
else:
publicKeyString = file(‘public.key’).read()
privateKeyString = file(‘private.key’).read()
return publicKeyString, privateKeyString
if __name__ == "__main__":
sshFactory = factory.SSHFactory()
sshFactory.portal = portal.Portal(SSHDemoRealm())
users = {‘admin’: ‘aaa’, ‘guest’: ‘bbb’}
sshFactory.portal.registerChecker(
checkers.InMemoryUsernamePasswordDatabaseDontUse(**users))
pubKeyString, privKeyString =
getRSAKeys()
sshFactory.publicKeys = {
‘ssh-rsa’: keys.getPublicKeyString(data=pubKeyString)}
sshFactory.privateKeys = {
‘ssh-rsa’: keys.getPrivateKeyObject(data=privKeyString)}
from twisted.internet import reactor
reactor.listenTCP(2222, sshFactory)
reactor.run()
{mospagebreak title=Setting Up a Custom SSH Server continued}
sshserver.py will run an SSH server on port 2222. Connect to this server with an SSH client using the username admin and password aaa, and try typing some commands:
$ ssh admin#localhost -p 2222
admin#localhost’s password: aaa
>>> Welcome to my test SSH server.
Commands: clear echo help quit whoami
$ whoami
admin
$ help echo
Echo a string. Usage: echo my line of text
$ echo hello SSH world!
hello SSH world!
$ quit
Connection to localhost closed.

adding here to driquet's answer as the edit waitlist is full
for python3 :
from pexpect import pxssh
s = pxssh.pxssh()
if not s.login ('10.6.192.18', 'root', 'paloalto'):
print ("SSH session failed on login.")
print (str(s))
else:
print ("SSH session login successful")
s.sendline ('ls -l')
s.prompt() # match the prompt
print (s.before.decode('UTF-8')) # decode to string and print everything before the prompt.
s.logout()

Pexpect - silence ssh connection output

I'm using a simple pexpect script to ssh to a remote machine and grab a value returned by a command.
Is there any way, pexpect or sshwise I can use to ignore the unix greeting?
That is, from
child = pexpect.spawn('/usr/bin/ssh %s#%s' % (rem_user, host))
child.expect('[pP]assword: ', timeout=5)
child.sendline(spass)
child.expect([pexpect.TIMEOUT, prompt])
child.before = '0'
child.sendline ('%s' % cmd2exec)
child.expect([pexpect.EOF, prompt])
# Collected data processing
result = child.before
# logon to the machine returns a lot of garbage, the returned executed command is at the 57th position
print result.split('\r\n') [57]
result = result.split('\r\n') [57]
How can I simply get the returned value, ignoring,
the "Last successful login" and "(c)Copyright" stuff
and without having to concern with the value correct position?
Thanks !

If you have access to the server to which you are logging in, you can try creating a file named .hushlogin in the home directory. The presence of this file silences the standard MOTD greeting and similar stuff.
Alternatively, try ssh -T, which will disable terminal allocation entirely; you won't get a shell prompt, but you may still issue commands and read the response.
There is also a similar thread on ServerFault which may be of some use to you.

If the command isn't interactive, you can just run ssh HOST COMMAND to run the command without all the login excitement happening at all. If the command is interactive, you can frequently use the ssh -t option (ssh -t HOST COMMAND) to force pseudo-tty allocation and trick the remote process to think that it's running attached to a TTY.

I have used paramiko to automate ssh connection and I have found it useful. It can deal with greetings and silent execution.
http://www.lag.net/paramiko/

Hey there you kann kill all that noise by using the sys module and a small class:
class StreamToLogger(object):
"""
Fake file-like stream object that redirects writes to a logger instance.
"""
def __init__(self, logger, log_level=logging.INFO):
self.logger = logger
self.log_level = log_level
self.linebuf = ''
def write(self, buf):
for line in buf.rstrip().splitlines():
self.logger.log(self.log_level, line.rstrip())
#Mak
stdout_logger = logging.getLogger('STDOUT')
sl = StreamToLogger(stdout_logger, logging.INFO)
sys.stdout = sl
stderr_logger = logging.getLogger('STDERR')
sl = StreamToLogger(stderr_logger, logging.ERROR)
sys.stderr = sl
Can't remember where i found that snippet but it works for me :)