Pfthb

I have a list of hostnames / IP addresses, and my script takes the each item from the text file and stores them in the nodes variable as a list.

I want to ping each host and output the results to a text file. I can do it with a single host, but am having trouble understanding how to iterate through the list.

I have looked at other posts on Stackoverflow, but most of the posts are using the OS module, which has been deprecated.

My code:

#!/usr/local/bin/python3.6

import argparse
import subprocess


parser = argparse.ArgumentParser(description="Reads a file and pings hosts by line.")
parser.add_argument("filename")

args = parser.parse_args()

# Opens a text file that has the list of IP addresses or hostnames and puts
#them into a list.
with open(args.filename) as f:
 lines = f.readlines()
 nodes = [x.strip() for x in lines]

# Opens the ping program
ping = subprocess.run(
 ["ping", "-c 1", nodes[0]],
 stdout=subprocess.PIPE,
 stderr=subprocess.PIPE
)

# Captures stdout and puts into a text file.
with open('output.txt', 'w') as f:
 print(ping.stdout.decode(), file=f)
 f.close()

You can iterate directly through your list of nodes like so:

with open(args.filename) as f:
 lines = f.readlines()
 nodes = [x.strip() for x in lines]

with open('output.txt', 'w') as f:
 for node in nodes:
 # Opens the ping program
 ping = subprocess.run(
 ["ping", "-c 1", node],
 stdout=subprocess.PIPE,
 stderr=subprocess.PIPE
 )
 # Captures stdout and puts into a text file.
 print(ping.stdout.decode(), file=f)

Note that you can also directly iterate over your input file, which is said to be more 'Pythonic' than using readlines():

with open(args.filename,'r') as infile, open('output.txt', 'w') as outfile:
 for line in infile:
 node = line.strip()
 # Opens the ping program
 ping = subprocess.run(
 ["ping", "-c 1", node],
 stdout=subprocess.PIPE,
 stderr=subprocess.PIPE
 )
 # Captures stdout and puts into a text file.
 print(ping.stdout.decode(), file=outfile)

Note that this is untested, but I can't see any obvious errors.

Just iterate through the nodes list like this:

for i in nodes: 
 ping = subprocess.run(
 ["ping", "-c 1", i],
 stdout=subprocess.PIPE,
 stderr=subprocess.PIPE)

Hope it helps :)