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✏️ Editing: hostname.py

# Copyright (C) 2012 Yahoo! Inc.
#
# Author: Joshua Harlow <harlowja@yahoo-inc.com>
#
# This file is part of cloud-init. See LICENSE file for license information.

from io import StringIO

from cloudinit.distros.parsers import chop_comment

# Parser that knows how to work with /etc/hostname format
class HostnameConf:
    def __init__(self, text):
        self._text = text
        self._contents = None

def parse(self):
        if self._contents is None:
            self._contents = self._parse(self._text)

def __str__(self):
        self.parse()
        contents = StringIO()
        for (line_type, components) in self._contents:
            if line_type == "blank":
                contents.write("%s\n" % (components[0]))
            elif line_type == "all_comment":
                contents.write("%s\n" % (components[0]))
            elif line_type == "hostname":
                (hostname, tail) = components
                contents.write("%s%s\n" % (hostname, tail))
        # Ensure trailing newline
        contents = contents.getvalue()
        if not contents.endswith("\n"):
            contents += "\n"
        return contents

@property
    def hostname(self):
        self.parse()
        for (line_type, components) in self._contents:
            if line_type == "hostname":
                return components[0]
        return None

def set_hostname(self, your_hostname):
        your_hostname = your_hostname.strip()
        if not your_hostname:
            return
        self.parse()
        replaced = False
        for (line_type, components) in self._contents:
            if line_type == "hostname":
                components[0] = str(your_hostname)
                replaced = True
        if not replaced:
            self._contents.append(("hostname", [str(your_hostname), ""]))

def _parse(self, contents):
        entries = []
        hostnames_found = set()
        for line in contents.splitlines():
            if not len(line.strip()):
                entries.append(("blank", [line]))
                continue
            (head, tail) = chop_comment(line.strip(), "#")
            if not len(head):
                entries.append(("all_comment", [line]))
                continue
            entries.append(("hostname", [head, tail]))
            hostnames_found.add(head)
        if len(hostnames_found) > 1:
            raise IOError("Multiple hostnames (%s) found!" % (hostnames_found))
        return entries

MR SKB