SFTP in Python: Really Simple SSH

SFTP in Python: Really Simple SSH

Posted on May 29, 2008 by zeth ssh.py provides three common SSH operations, get, put and execute. It is a high-level abstraction upon Paramiko.

I wrote it yesterday for my own needs, so it is still very much in the beta stage. Any improvements or comments gratefully accepted.

In short, it works as follows:

import ssh
s = ssh.Connection('example.com')
s.put('hello.txt')
s.get('goodbye.txt')
s.execute('du -h --max-depth=0')
s.close()

That is it, in the rest of this post, I walk through this line by line.

Installation

First, we need to install paramiko, if you don't have it already.

On Gentoo Linux:

emerge paramiko

On Ubuntu/Debian and so on:

apt-get install python-paramiko

If you want to use Python's easy_install then:

easy_install paramiko

Secondly, you need to grab the ssh.py module, grab it from my code-page, and save it as ssh.py.

Connecting to a remote server

To play with the script interactively, you need to start Python:

python

Now, import the ssh module:

import ssh

Next we need to initiate the connection. If your username is the same on both systems, and you have set up ssh-keys, then all you need to do is:

s = ssh.Connection('example.com')

Connection supports the following options:

host	The Hostname of the remote machine.
username	Your username at the remote machine.
private_key	Your private key file.
password	Your password at the remote machine.
port	The SSH port of the remote machine.

The host is essential of course. Port defaults to 22. The username defaults to the username you are currently using on the local machine.

You need to use one of the authentication methods, a private key or a password. If you don't specify anything, then ssh.Connection will attempt to use a private_key at ~/.ssh/id_rsa or ~/.ssh/id_dsa.

So to specify a username and password, you can do it like this:

s = ssh.Connection(host = 'example.com', username = 'warrior', password = 'lennalenna')

Of course, Python also allows you to use the order to specify the arguments, so the last example can be written as:

s = ssh.Connection('example.com', 'warrior', password = 'lennalenna')

Operations

Once you have set up the connection, there are three methods you can use. Firstly, to send a file from the local machine, you can use put:

s.put('hello.txt')

The above example copies a file called hello.txt from the current local working directory to the remote server. We can also be more explicit if we want:

s.put('/home/warrior/hello.txt', '/home/zombie/textfiles/report.txt')

So the above example copies /home/warrior/hello.txt on the local server to /home/zombie/textfiles/report.txt on the remote server.

The second operation works in a similar way but in reverse:

s.get('hello.txt')

get takes the file from the remote server to the local server, again we can be more explicit if we want:

s.get('/var/log/strange.log', '/home/warrior/serverlog.txt')

The above example copies the strange.log from the server and saves it as serverlog.txt.

The last operation is execute, this executes a command on the remote server:

s.execute('ls -l')

This returns the output as a Python list.

Closing the connection

You can do as many operations you like while the connection is open, but when you are finished, you need to close the connection between the local and remote machines. You do this with the close method:

s.close()

There we go, that is all I needed to do with SSH. Please do let me know using the comments below if you have any problems using it.

If you import my module in your program and later find that you need more power or flexibility, you should be able to swap it out for the full paramiko with a minimum of fuss.

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