2

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" " [email protected]" " 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

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5
  • does the ssh have password? If it does the above would not work. Commented May 21, 2013 at 4:33
  • You have %s but then you use +; its not doing what you think its doing. Commented May 21, 2013 at 4:36
  • 3
    @BurhanKhalid in this case %s is not meant for Python, but for the stat command (it means "show the total size in bytes") Commented May 21, 2013 at 4:39
  • Oh I see; however seeing the multiple " " in the string doesn't give me much confidence :) Commented May 21, 2013 at 4:44
  • You'll need to use stat -c%s on the local file aswell.. Commented May 21, 2013 at 5:24

4 Answers 4

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3

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 [email protected] stat -c%s "{}"'.format(B), shell=True)
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1 Comment

Note: to do it without shell=True, which is not usually required, you will need to use the absolute path of stat (find with which stat) and split the command into an args list (using shlex.split)
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

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1 Comment

all, i appriciate your help! below code helped me to solve my prob, posted by Brian Cain : statinfo1 = os.stat(A).st_size cmd = "ssh" " [email protected]" " 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
1

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 = ['[email protected]']
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"
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Comments

0 
statinfo1 = os.stat(A)
statinfo2 = os.system ("ssh" " [email protected]" " 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" " [email protected]" " 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
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5 Comments

Deprecated since version 2.6: The commands module has been removed in Python 3. Use the subprocess module instead.
i would really appriciate if someone could help me to understand whatis: rc, remote_stat and what does 'if rc != 0' means
@Noob, if you're satisfied with these answer(s), please select one as the official answer to your question.
@wim, indeed, subprocess is a better alternative.
sure Brian and Win. both your solutions worked fine for me. i appriciate alot! thanks again

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