CODEWITHSUNDEEP
pythonparsingsubprocess
nullByteMe
nullByteMe

Reputation: 6391

How to parse results from a subprocess

I'm trying to pass a string in Python that was obtained from netstat to awk for use in building a new object.

Any clue why this isn't working? Please excuse the horrible coding, I just started using Python today and trying to learn how to use the language.

class NetstatGenerator():

    def __init__(self):
    import subprocess
    self.results = subprocess.Popen("netstat -anbp tcp", shell=True, stdout=subprocess.PIPE).stdout.read()
    self.list = []
    self.parse_results()

def parse_results(self):
    lines = self.results.splitlines(True)
    for line in lines:
        if not str(line).startswith("tcp"):
            print("Skipping")
            continue

        line_data = line.split(" ")
        self.list.append(NetstatData(self.line_data[0], self.line_data[15], self.line_data[18], self.line_data[23]))

def get_results(self):
    return self.list

class NetstatData():

    def __init__(self, protocol, local_address, foreign_address, state):
        self.protocol = protocol
        self.local_address = local_address
        self.foreign_address = foreign_address
        self.state = state

    def get_protocol(self):
        return str(self.protocol)

    def get_local_address(self):
        return str(self.local_address)

    def get_foreign_address(self):
        return str(self.foreign_address)

    def get_state(self):
        return str(self.state)

data = NetstatGenerator()

Upvotes: 1

Views: 2204

Answers (1)

9000
9000

Reputation: 40894

Sorry, netstat does not support -b on Linux, and I don't have a BSD box lying around.

Let's assume you have a list of lines, called netstat_output, with items like this:

tcp 0 0 127.0.0.1:9557 127.0.0.1:56252 ESTABLISHED -

To parse a single line, you split() it and pick elements at indexes 0, 3, 4, 5.

To store the items, you don't need to define a boilerplate holding class; namedtuple does what you want:

from collections import namedtuple

NetstatInfo = namedtuple('NetstatInfo', 
    ['protocol', 'local_address', 'remote_address', 'state'])

Now you can parse a line:

def parseLine(line):
  fields = line.split()
  if len(fields) == 7 and fields[0] in ('tcp', 'udp'):  
    # alter this condition to taste; 
    # remember that netstat injects column headers.
    # consider other checks, too.
    return NetstatInfo(fields[0], fields[3], fields[4], fields[5])
  # otherwise, this function implicitly returns None

Now something like this must be possible:

result = []

for line in subprocess.Popen(...):
  item = parseLine(line)
    if line:  # parsed successfully
      result.append(line)

# now result is what you wanted; e.g. access result[0].remote_address

Upvotes: 2

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