Executing shell commands in Python

Question

I'm working in Linux/Python 3 and am creating some small scripts which consist of executing some commands inside of Python.

Example: Pinging a server

hostname= "server.com"
response= os.system("ping -c 1 " + hostname)
if response == 0:
    print (hostname, 'is up!')
else:
    print (hostname, 'is down!')

Output:

PING server.com (10.10.200.55) 56(84) bytes of data.
64 bytes from server.com (10.10.200.55): icmp_seq=1 ttl=61 time=12.4 ms

--- server.com ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 15.446/15.446/15.446/0.000 ms
server.com is up!

This is working OK but I don´t need to print everything. How can I get only the first line of the output?

Hey are you on linux or windows?

Brody Critchlow
– Brody Critchlow

2022-08-17 18:02:55 +00:00
Commented Aug 17, 2022 at 18:02 — Brody Critchlow
– Brody Critchlow, Commented Aug 17, 2022 at 18:02
Hey there. I am in Linux

fr0zt
– fr0zt

2022-08-18 08:22:49 +00:00
Commented Aug 18, 2022 at 8:22 — fr0zt
– fr0zt, Commented Aug 18, 2022 at 8:22
Which version of Python 3 are you using?

Daniel Walker
– Daniel Walker

2022-08-18 13:40:56 +00:00
Commented Aug 18, 2022 at 13:40 — Daniel Walker
– Daniel Walker, Commented Aug 18, 2022 at 13:40

Patrick · Accepted Answer · 2022-08-18 14:06:05Z

4

You can use a subprocess in python3 to discard the output to devnull. Something like this

import subprocess

hostname= "server.com"
response= subprocess.call(["ping", "-c", "1", hostname], 
stdout=subprocess.DEVNULL,
stderr=subprocess.STDOUT)

if response == 0:
  print (hostname, 'is up!')
else:
  print (hostname, 'is down!')

https://docs.python.org/3/library/subprocess.html#subprocess.DEVNULL

edited Aug 18, 2022 at 14:06

answered Aug 17, 2022 at 18:13

Patrick

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5 Comments

Maurice Meyer Over a year ago

check_output has no stdout flag.

fr0zt Over a year ago

I get this error: raise ValueError('stdout argument not allowed, it will be overridden.') ValueError: stdout argument not allowed, it will be overridden.

Patrick Over a year ago

Apologies. changed it to call. Should work now.

fr0zt Over a year ago

Looks nice now. Thanks. How can I get the first line of the output for example?

Patrick Over a year ago

youd have to set response= subprocess.check_output(["ping", "-c", "1", hostname]) then parse that response manually. You'd also have to use a try/except because if host is invalid it will throw an exception

Patrick · Accepted Answer · 2022-08-18 20:29:22Z

0

Answer that prints the opening response as well. You may have to tweak the response if you don't want to handle it as a byte string and to handle valid but down hosts.

import subprocess

hostname= "stackoverflow.com"
try:
    response= subprocess.check_output(["ping", "-c", "1", hostname])
    print (response.split(b'\n')[0])
    print (hostname, 'is up!')
except subprocess.CalledProcessError:
    print (hostname, 'is down!')

answered Aug 18, 2022 at 20:29

Patrick

1697 bronze badges

2 Comments

fr0zt Over a year ago

Output: b'PING stackoverflow.com (151.101.193.69) 56(84) bytes of data.' Anyway to get rid of the b' and last ', from the output?

Patrick Over a year ago

you'd have to convert the byte string to a regular string. you can try wrapping it in str() but I'm not 100% on that.

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