CODEWITHSUNDEEP
pythonsubprocess
Malintha
Malintha

Reputation: 4766

How to run port lookup command in python subprocess

I am using terminal command 

while ! echo exit | nc 10.0.2.11 9445; do sleep 10; done

in my commandline to lookup port in my remote machine.( it is working fine). I want to do this operation inside my python script. I found subprocess and I want to know that how can I do this with subprocess ?

from subprocess import call
call(["while xxxxxxxxxxxxxxxxxxxxxxxxxxx"])

Upvotes: 0

Views: 236

Answers (1)

hlt
hlt

Reputation: 6317

subprocess.call does not by default use a shell to run its commands. Therefore, things like while are unknown commands. Instead, you could pass shell=True to call (security risk with dynamic data and user input*) or call the shell directly (the same advice applies):

from subprocess import call
call("while ! echo exit | nc 10.0.2.11 9445; do sleep 10; done", shell="True")

or directly with the shell, this is (a) less portable (because it assumes a specific shell) and (b) more secure (because you can specify what shell is to be used as syntax is not unified over different shells, e.g. csh vs. bash, and usage on other shells may lead to undefined or unwanted behaviour):

from subprocess import call
call(["bash", "-c", "while ! echo exit | nc 10.0.2.11 9445; do sleep 10; done"])

The exact argument to the shell to execute a command (here -c) depends on your shell.

You may want to have a look at the subprocess docs, especially for other ways of invoking processes. See e.g. check_call as a way of checking the return code for success, check_output to get the standard output of the process and Popen for advanced input/output interaction with the process.

Alternatively, you could use os.system, which implicitly launches a shell and returns the return code (subprocess.check_call with shell=True is a more flexible alternative to this)

* This link is to the Python 2 docs instead of the Python 3 docs used otherwise because it better outlines the security problems

Upvotes: 1

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