如何在python子进程中运行端口查找命令

Question

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"])

Answer 1

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, eg 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 eg 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