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#!/usr/bin/env python
# -*- test-case-name: twisted.names.test.test_examples -*-
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.
"""
Print the IP address for a given hostname. eg
python gethostbyname.py www.google.com
This script does a host lookup using the default Twisted Names
resolver, a chained resolver, which attempts to lookup a name from:
* local hosts file
* memory cache of previous lookup results
* system recursive DNS servers
"""
import sys
from twisted.internet.task import react
from twisted.names import client, error
from twisted.python import usage
class Options(usage.Options):
synopsis = "Usage: gethostbyname.py HOSTNAME"
def parseArgs(self, hostname):
self["hostname"] = hostname
def printResult(address, hostname):
"""
Print the IP address or an error message if an IP address was not
found.
"""
if address:
sys.stdout.write(address + "\n")
else:
sys.stderr.write(f"ERROR: No IP addresses found for name {hostname!r}\n")
def printError(failure, hostname):
"""
Print a friendly error message if the hostname could not be
resolved.
"""
failure.trap(error.DNSNameError)
sys.stderr.write(f"ERROR: hostname not found {hostname!r}\n")
def main(reactor, *argv):
options = Options()
try:
options.parseOptions(argv)
except usage.UsageError as errortext:
sys.stderr.write(str(options) + "\n")
sys.stderr.write(f"ERROR: {errortext}\n")
raise SystemExit(1)
hostname = options["hostname"]
d = client.getHostByName(hostname)
d.addCallback(printResult, hostname)
d.addErrback(printError, hostname)
return d
if __name__ == "__main__":
react(main, sys.argv[1:])
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