Need to pass object in a python array in bash

Question

I am trying to get the response code for three sites using the below python code snippet. But wondering how I can parse each object in the array to pass through the for loop within the curl call.

import os

servers = ["google", "yahoo", "nonexistingsite"]
for i in range(len(servers)):
    print(os.system('curl --write-out "%{http_code}\n" --silent --output'
                    ' /dev/null "https://servers[i].com"'))

With the above code, it's not getting passed through servers[i].

Don't use os.system to run curl; use something like the requests library to make HTTP requests from within the Python program. — chepner
– chepner, Commented Oct 27, 2018 at 20:49

willeM_ Van Onsem · Accepted Answer · 2018-10-27 19:28:03Z

3

You need to perform string formatting, like:

import os

servers = ["google", "yahoo", "nonexistingsite"]
for server in servers:
  print(os.system('curl --write-out "%{{http_code}}\\n" --silent --output /dev/null "https://{}.wellsfargo.com"'.format(server)))

The above can however still go wrong, if for example the servers contain quotes, etc.

It might be better to here use subprocess.run and pass it a list of parameters, like:

servers = ["google", "yahoo", "nonexistingsite"]
for server in servers:
    p = subprocess.run(
        [
            'curl'
            '--write-out',
            '%{http_code}\\n',
            '--silent',
            '--output'
            '/dev/null',
            'https://{}.wellsfargo.com'.format(server)
        ],
        shell=True,
        capture_output=True
    )

edited Oct 27, 2018 at 19:28

answered Oct 27, 2018 at 18:52

willeM_ Van Onsem

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5 Comments

Gladiator Over a year ago

Mine is Python 2.7.10 and i believe subprocess.run module works for 3.5 and later. So i tried your first option, even though it worked - there are two output for each server in the loop. One is the actual 200 OK or a 404 result expected and the additional one is 0 or 1536. Not sure where it comes from.

import os      servers = ["google", "yahoo", "non-existsite"]      for server in servers:        print(os.system('curl --write-out "%{{http_code}}\n" --silent --output /dev/null "https://www.{}.com"'.format(server)))

willeM_ Van Onsem Over a year ago

@martineau: thanks. I think with escaping it, it might be solved.

willeM_ Van Onsem Over a year ago

@Gladiator: well If I run this locally, I got this error as well, since it can not resolve the host yahoo.wellsfargo.com. Are you sure that domain name exists?

martineau Over a year ago

Gladiator: subprocess.run() should work fine in Python 2.

Gladiator Over a year ago

@WillemVanOnsem that is correct, yahoo.wellsfargo.com doesn't exist. I corrected it on the last comment. The edited code is as below;

import os servers = ["google", "yahoo", "non-existsite"] for server in servers: print(os.system('curl --write-out "%{{http_code}}\n" --silent --output /dev/null "https://www.{}.com"'.format(server)))

This gives two response codes for each server in the loop.

mikeb · Accepted Answer · 2018-10-27 19:24:21Z

1

Try using Python's string formatting, something like:

"This string uses an %s" %(argument) would become "This string uses an argument"

Something like this:

print(os.system('curl --write-out "%%{http_code}\n" --silent --output /dev/null "https://%s.wellsfargo.com"') % (servers[i])

More here: https://powerfulpython.com/blog/python-string-formatting/

edited Oct 27, 2018 at 19:24

answered Oct 27, 2018 at 18:52

mikeb

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3 Comments

willeM_ Van Onsem Over a year ago

I think you need to escape the "%{http_code}\n" part here, since otherwise it looks for a http_code parameter in the formatting call.

mikeb Over a year ago

Good call, %% escapes it

martineau Over a year ago

I think you need to escape the backslash in \n, too.

chepner · Accepted Answer · 2018-10-27 20:53:24Z

0

Just use the requests library instead of shelling out to run curl:

for s in servers:
    resp = requests.get(s)
    print(resp.status_code)

Since you don't care about the body of the response, only whether it responds, you could save bandwidth by using the head function instead of get to retrieve only the headers from the server.

answered Oct 27, 2018 at 20:53

chepner

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