子进程运行命令直到第一个管道，然后停止

Question

If i run this command on its own:

nmap -PN -p 22 --open -oG - 10.15.86.0/24 | awk '$NF~/ssh/{print$2}' > sshopen.txt

I receive my desired output of:

10.15.86.4
10.15.86.5
10.15.86.9
10.15.86.11
etc...

All the hosts on my network with an open ssh port. However, when i try to run the same command within a Python subprocess, it seems to skip the awk. Python below:

import subprocess

subnet = raw_input("Enter subnet to scan: ")
command1 = "nmap -PN -p 22 --open -oG - 10.15.86.0/24 | awk '$NF~/ssh /{print$2}' > sshopen.txt".split()
#command = ["nmap", "-PN", "-p", "22", "--open", "-oG", "-", subnet, "|", "awk", "'$NF~/ssh/{print $2}'", ">", "sshopen.txt"]
nmap = subprocess.Popen(command1, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
nmap_info, out = nmap.communicate()  
print nmap_info

You'll notice the commented 'command', as i've tried as 'command' and 'command1'. Both return output of:

Host: 10.15.86.4 () Status: Up
Host: 10.15.86.4 () Ports: 22/open/tcp//ssh///
Host: 10.15.86.5 () Status: Up
Host: 10.15.86.5 () Ports: 22/open/tcp//ssh///
etc...

It outputs as though there is no pipe awk (nmap -PN -p 22 --open -oG - 10.15.86.0/24) rather than (nmap -PN -p 22 --open -oG - 10.15.86.0/24 | awk '$NF~/ssh/{print$2}' > sshopen.txt). Why is it not applying the awk within the script?

Thanks

Answer 1

Try

p1 = Popen(["nmap", "-PN", "-p", "22", "--open", "-oG", "-", subnet], stdout=PIPE)
p2 = Popen(["awk", "$NF~/ssh/{print$2}"], stdin=p1.stdout, stdout=PIPE)
p1.stdout.close()
output = p2.communicate()[0]

or

check_output(command, shell=True)

This is from python's official subprocess doc .

There are some security considerations with shell=True though.

Unlike some other popen functions, this implementation will never implicitly call a system shell. This means that all characters, including shell metacharacters, can safely be passed to child processes. If the shell is invoked explicitly, via shell=True, it is the application's responsibility to ensure that all whitespace and metacharacters are quoted appropriately to avoid shell injection vulnerabilities.

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1. https://docs.python.org/3/library/subprocess.html#replacing-shell-pipeline
2. https://docs.python.org/3/library/subprocess.html#security-considerations