checking file size in a remote server using python

Question

someone please help!

im currently writting a python script to actually retrieve a file size that is in a local PC and a remote server. then, what i do is, i compare if the file's size are the same. below is my code :

A = "/path/of/the/file/in/my/local/PC"
B = "/path/of/the/file/in/remote/PC"

statinfo1 = os.stat(A)
statinfo2 = os.system ("ssh" " root@192.168.10.1" " stat -c%s "+B)

if statinfo1 == statinfo2 :
   print 'awesome'
else :
   break

problem encountered : statinfo1 is able to return the file size in the local PC, but statinfo2 is not able to return the file size.. anyone please help? i want to use SSH method

Answer 1

Using paramiko or pexpect will work, but may be kind of heavyweight for your simple use case here.

You can use a lightweight solution that simply relies on ssh of the underlying OS, and python builtin subprocess module.

import os
A = "/path/of/the/file/in/my/local/PC"
B = "/path/of/the/file/in/remote/PC"

# I assume you have stat visible in PATH on both the local and remote machine,
# and that you have no password nags for ssh because you've setup the key pairs 
# already (using, for example, ssh-copy-id)

statinfo1 = subprocess.check_output('stat -c%s "{}"'.format(A), shell=True)
statinfo2 = subprocess.check_output('ssh root@192.168.10.1 stat -c%s "{}"'.format(B), shell=True)

Answer 2

Why dont you use Paramiko SSHClient. Its a nifty third party library simplifying ssh access.

So to check file size of remote file the code would be something like -

import paramiko, base64

B = "/path/of/the/file/in/remote/PC"

key    = paramiko.RSAKey(data=base64.decodestring('AAA...'))
client = paramiko.SSHClient()
client.get_host_keys().add('ssh.example.com', 'ssh-rsa', key)
client.connect('192.168.10.1', username='root', password='yourpassword')
stdin, stdout, stderr = client.exec_command("stat -c " + B)
for line in stdout:
    print '... ' + line.strip('\n')
client.close()

Check this too - How to get size of remote file? and SSH programming with Paramiko

Answer 3

statinfo1 = os.stat(A)
statinfo2 = os.system ("ssh" " root@192.168.10.1" " stat -c%s "+B)

What does os.stat return?

• a data structure with several fields, one of which is the size.

what does os.system return?

• it returns an int representing the exit code of the program invoked.

So the comparison between them is bound to fail. Consider Paramiko as @Srikar suggests, or address the issues with this approach.

For the latter, try this:

import commands

statinfo1 = os.stat(A).st_size
cmd = "ssh" " root@192.168.10.1" " stat -c%s "+B
rc, remote_stat = commands.getstatusoutput(cmd)

if rc != 0:
   raise Exception('remote stat failure: ' + remote_stat)

statinfo2 = int(remote_stat)

if statinfo1 == statinfo2 :
   print 'awesome'
else :
   break

Answer 4

You could also take a look at fabric for easy remote tasks.

fabfile.py:

1 from fabric.api import run, env
2
3 env.hosts = ['[e-mail]']
4
5 def get_size(remote_filename):
6     output = run('stat -c \'%s\' {0}'.format(remote_filename))
7     print 'size={0}'.format(output)

Shell command:

~ $ fab get_size:"~/.bashrc"