how to get console output from a remote computer (ssh + python)

Question

I have googled "python ssh". There is a wonderful module pexpect, which can access a remote computer using ssh (with password).

After the remote computer is connected, I can execute other commands. However I cannot get the result in python again.

p = pexpect.spawn("ssh user@remote_computer")
print "connecting..."
p.waitnoecho()
p.sendline(my_password)
print "connected"
p.sendline("ps -ef")
p.expect(pexpect.EOF) # this will take very long time
print p.before

How to get the result of ps -ef in my case?

hmm? p.before should give the output

Anurag Uniyal
– Anurag Uniyal

2009-08-21 12:56:09 +00:00
Commented Aug 21, 2009 at 12:56 — Anurag Uniyal
– Anurag Uniyal, Commented Aug 21, 2009 at 12:56

Pavel Repin · Accepted Answer · 2009-08-21 23:07:00Z

14

Have you tried an even simpler approach?

>>> from subprocess import Popen, PIPE
>>> stdout, stderr = Popen(['ssh', 'user@remote_computer', 'ps -ef'],
...                        stdout=PIPE).communicate()
>>> print(stdout)

Granted, this only works because I have ssh-agent running preloaded with a private key that the remote host knows about.

answered Aug 21, 2009 at 23:07

Pavel Repin

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2 Comments

stanleyxu2005 Over a year ago

Thanks for this tip. Is there an easy way to configure private keys for many clients? I have to check log files of 20 machines every week. This is the motivation of writing a python script.

Pavel Repin Over a year ago

Well... you'll just have to append your public key to ~/.ssh/authorized_keys on each of the machines. Perhaps, if your working set of machines doesn't change a lot, this will be a one time exercise. BTW, this is a pretty neat article about setting up SSH Agent and more: unixwiz.net/techtips/ssh-agent-forwarding.html

avasal · Accepted Answer · 2011-08-25 08:21:01Z

3

child = pexpect.spawn("ssh user@remote_computer ps -ef")
print "connecting..."
i = child.expect(['user@remote_computer\'s password:'])
child.sendline(user_password)
i = child.expect([' .*']) #or use i = child.expect([pexpect.EOF])
if i == 0:
    print child.after # uncomment when using [' .*'] pattern
    #print child.before # uncomment when using EOF pattern
else:
    print "Unable to capture output"


Hope this help..

edited Aug 25, 2011 at 8:21

answered Aug 25, 2011 at 6:32

avasal

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Comments

JJ Geewax · Accepted Answer · 2009-08-21 19:08:36Z

1

You might also want to investigate paramiko which is another SSH library for Python.

answered Aug 21, 2009 at 19:08

JJ Geewax

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1 Comment

stanleyxu2005 Over a year ago

After having tried so many different solutions, I think this library is the best practice for now. I even do not have to configure non-password login to run any script on foreign nodes over LAN.

Aaron Digulla · Accepted Answer · 2009-08-21 15:43:45Z

1

Try to send

p.sendline("ps -ef\n")

IIRC, the text you send is interpreted verbatim, so the other computer is probably waiting for you to complete the command.

answered Aug 21, 2009 at 15:43

Aaron Digulla

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