#!/usr/bin/env python2
# this script add aliases to /etc/hosts
import sys, re

if len(sys.argv) < 2 or len(sys.argv) > 3:
    sys.exit(1)

host = sys.argv[1]
alias = sys.argv[2] if len(sys.argv) == 3 else "localhost"

if host == "localhost" or host == alias:
    sys.exit(0)

print "Adding host {} as an alias of {}".format(host, alias)
with open("/etc/hosts", "r+") as f:
    buf = re.sub(r"\b{}\b".format(alias), "{}\t{}".format(alias, host), f.read(), 1)
    f.seek(0)
    f.write(buf)