Python：在成功的ping上在Cisco路由器中执行命令，否则打印错误

Question

The following code fetches IP address (Cisco Router) from a text file and executes the mentioned command and prints the resultant output on to a file. Here am trying to first test the reach-ability of the device by using PING, on successful ping response commands should be executed else should print an error and move to the next host. Please help me on how to achieve this. I am a newbie.

Here is my code,

import paramiko
import sys
import os
import subprocess

with open('C:\Python27\Testing\Fetch.txt') as f:
    for line in f:
        line = line.strip()
        dssh = paramiko.SSHClient()
        dssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
        dssh.connect(line, username='cisco', password='cisco')
        stdin, stdout, stderr = dssh.exec_command('sh ip ssh')
        mystring = stdout.read()
        print mystring
        f = open('C:\Python27\Testing\output.txt', 'a+')
        f.write(mystring)
        f.close()      
dssh.close()

Input file Fetch.txt looks like this,

10.0.0.1
10.0.0.2
10.0.0.3
10.0.0.4
10.0.0.5

---

I scoured through the forum and achieved just about what I am looking for.. If all the IP addresses are reachable in that list, the script works just fine. But if any one of the IP address is unreachable then the script ends abruptly without proceeding to the next IP address. I realize that am doing something wrong here, I just need that little bit of help to get this working..... Please help out.

import paramiko
import sys
import os
import subprocess
dssh = paramiko.SSHClient()
dssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())

with open('C:\Python27\Testing\Fetch.txt') as f:
     for line in f:
        line = line.strip()
        with open(os.devnull, "wb") as limbo:
            ip = line
            result = subprocess.Popen(["ping", "-n", "1", "-w", "200", ip],
                                      stdout=limbo, stderr=limbo).wait()
            if result: 
                    print ip, "Down"   
            else:   
                    print ip, "Reachable"  
    dssh.connect(line, username='cisco', password='cisco')
    stdin, stdout, stderr = dssh.exec_command('sh ip ssh')
    mystring = stdout.read()
    print mystring
    f = open('C:\Python27\Testing\output.txt', 'a+')
    f.write('\n' + ip + '\n' + mystring)
    f.close()      
dssh.close()

Answer 1

You ideally don't have to test if a host is pingable first using a separate if statement..paramiko comes inbuilt with a lot of exception checking ..using this along the socket module..your program can be written in a cleaner fashion without having to use subprocesses..

import paramiko
import socket
dssh = paramiko.SSHClient()
dssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ips = [i.strip() for i in open("C:\Python27\Testing\Fetch.txt")] # creates a list from input file

for ip in ips:
    try:
        dssh.connect(ip, username='cisco', password='cisco', timeout=4)
        stdin, stdout, stderr = ssh.exec_command('sh ip ssh')
        print ip + '===' + stdout.read()
        ssh.close()
    except paramiko.AuthenticationException:
        print ip + '=== Bad credentials'
    except paramiko.SSHException:
        print ip + '=== Issues with ssh service'
    except socket.error:
        print ip + '=== Device unreachable' 

this will catch other exceptions like bad credentials and other issues with ssh service

Answer 2

You could try using fabric which is made for executing SSH commands on multiple machines.

This is just a snippet i threw together but it should show you the way to go.

from fabric.api import run, execute ,env

class Fetcher:
  def __init__(self,hosts=[]):
    env.hosts= hosts
    env.warn_only = True  # needed to not abort on pingtimout or other errs

  def getclock(self)
    run('sh clock')

  def fetch(self):
    results = execute(self.getclock,hosts=env.hosts)


if __name__ == '__main__':
  hosts = loadfromtxt(hosts.txt)
  f = Fetcher(hosts=hosts)
  f.fetch()

Answer 3

I recall an example of python threading, either in the docs or in a book I read (don't remember the source) that does something like what you're trying to do. Something like this should work:

import sys
import os
import subprocess
from threading import Thread

class Pinger(Thread):
    def __init__ (self, ip):
        Thread.__init__(self)
        self.ip = ip
        self.status = False

    def __repr__(self):
        return "Pinger for '%s' status '%s'" % (self.ip, self.status)

    def run(self):
        with open(os.devnull, "wb") as limbo:
            # Changed the arguments because I don't have a windows ping.exe to test it on
            result = subprocess.Popen(["ping", "-c", "2", "-q", self.ip],
                                      stdout=limbo, stderr=limbo).wait()
            if result: 
#                print self.ip, "Down"   
                self.status = False
            else:   
#                print self.ip, "Reachable"  
                self.status = True


hosts = []
with open('Fetch.txt') as f:
    for line in f:
        host = Pinger(line.rstrip())
#        print host
        hosts.append(host)
        host.start()

for host in hosts:
    host.join()
    if host.status:
        print "Host '%s' is up" % host.ip
        #### Insert your ssh exec code here ####
        # dssh.connect(host.ip, username='cisco', password='cisco')
        # etc.
    else:    
        print "Host '%s' is down" % host.ip

Answer 4

Why do you need Paramiko module or to create an input if python can do itself ?

#!/usr/bin/python

import os

hostname = raw_input('Enter the Router Name: ')
routers = hostname.split(',')
print routers

for hostname in routers:
        response = os.system("ping -c5 " + hostname) 
        if response == 0:
            print(hostname, 'is up!')
        else:
            print(hostname, 'is down!')