Execute a command on Remote Machine in Python

Question

I am writing a program in python on Ubuntu, to execute a command ls -l on RaspberryPi, connect with Network.

Can anybody guide me on how do I do that?

Answer 1

Sure, there are several ways to do it!

Let's say you've got a Raspberry Pi on a raspberry.lan host and your username is irfan.

subprocess

It's the default Python library that runs commands.
You can make it run ssh and do whatever you need on a remote server.

scrat has it covered in his answer. You definitely should do this if you don't want to use any third-party libraries.

You can also automate the password/passphrase entering using pexpect.

paramiko

paramiko is a third-party library that adds SSH-protocol support, so it can work like an SSH-client.

The example code that would connect to the server, execute and grab the results of the ls -l command would look like that:

import paramiko

client = paramiko.SSHClient()
client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
client.connect('raspberry.lan', username='irfan', password='my_strong_password')

stdin, stdout, stderr = client.exec_command('ls -l')

for line in stdout:
    print line.strip('\n')

client.close()

fabric

You can also achieve it using fabric.
Fabric is a deployment tool which executes various commands on remote servers.

It's often used to run stuff on a remote server, so you could easily put your latest version of the web application, restart a web-server and whatnot with a single command. Actually, you can run the same command on multiple servers, which is awesome!

Though it was made as a deploying and remote management tool, you still can use it to execute basic commands.

# fabfile.py
from fabric.api import *

def list_files():
    with cd('/'):  # change the directory to '/'
        result = run('ls -l')  # run a 'ls -l' command
        # you can do something with the result here,
        # though it will still be displayed in fabric itself.

It's like typing cd / and ls -l in the remote server, so you'll get the list of directories in your root folder.

Then run in the shell:

fab list_files

It will prompt for an server address:

No hosts found. Please specify (single) host string for connection: irfan@raspberry.lan

---

A quick note: You can also assign a username and a host right in a fab command:

fab list_files -U irfan -H raspberry.lan

Or you could put a host into the env.hosts variable in your fabfile. Here's how to do it.

---

Then you'll be prompted for a SSH password:

[irfan@raspberry.lan] run: ls -l
[irfan@raspberry.lan] Login password for 'irfan':

And then the command will be ran successfully.

[irfan@raspberry.lan] out: total 84
[irfan@raspberry.lan] out: drwxr-xr-x   2 root root  4096 Feb  9 05:54 bin
[irfan@raspberry.lan] out: drwxr-xr-x   3 root root  4096 Dec 19 08:19 boot
...

Answer 2

Simple example from here:

import subprocess
import sys

HOST="www.example.org"
# Ports are handled in ~/.ssh/config since we use OpenSSH
COMMAND="uname -a"

ssh = subprocess.Popen(["ssh", "%s" % HOST, COMMAND],
                       shell=False,
                       stdout=subprocess.PIPE,
                       stderr=subprocess.PIPE)
result = ssh.stdout.readlines()
if result == []:
    error = ssh.stderr.readlines()
    print >>sys.stderr, "ERROR: %s" % error
else:
    print result

It does exactly what you want: connects over ssh, executes command, returns output. No third party library needed.

Answer 3

You may use below method with linux/ Unix 's built in ssh command.

   import os
   os.system('ssh username@ip  bash < local_script.sh >> /local/path/output.txt 2>&1')
   os.system('ssh username@ip  python < local_program.py >> /local/path/output.txt 2>&1')