Joshua D. Gardner

The personal website of a geek.

Location Script

On my sidebar is the "Where is Josh" box. This explains how it's done.

I have a DynDNS.org account with several hostnames in it. One is the CelloFellow.HomeLinux.net site that you are viewing and runs on my home server. Another is cellofellow.is-a-geek.org, which points to my laptop.

My script runs a DNS lookup on both the home and my laptop hostnames. If they are the same, then I'm at home. I also generate a list of all IP addresses in my university's subnet. If my IP address is in that list, then I'm at school. If it's neither, I'm somewhere else.

It's implemented as a python CGI script that returns data in various formats, including JSON. I have a little bit of jQuery JavaScript on my site that loads this JSON data and displays it.

Not perfect, as there'll be a delay as the DNS records change and I may be offline and somewhere else but it still say I'm at school for example. Still, rather fun.

Python Code

Here is the python code for the script. 

#!/usr/bin/env python
from socket import gethostbyname
import os, subprocess
import simplejson

# Get IP addresses of hostnames.
try:
    myip = gethostbyname('cellofellow.is-a-geek.org')
    homeip = gethostbyname('cellofellow.homelinux.net')
except:
    exit("Can't find hostnames. Network probably not working.")

# Get all IP addresses in Weber State's subnet.
schoolsubnetprefixes = [ '137.190.%d.' % x for x in range(208, 212) ]

schoolsubnet = [ prefix + str(x) 
                for prefix in schoolsubnetprefixes 
                for x in range(255) 
               ]

del schoolsubnetprefixes

# If laptop and home IPs are the same, I'm at home.
isAtHome = myip == homeip

# If laptop IP is in Weber's subnet, I'm at school.
isAtSchool = myip in schoolsubnet

# Function that formats the output according to the previously set variables.
def place(format='str'):
    if format=='json':
        return simplejson.dumps({
            'location': place('str'),
            'known': place('bool'),
            'ip': myip,
        })

    elif format=='bool':
        return isAtHome or isAtSchool
    
    if isAtHome:
        if format=='str':
            return "Josh is at home."
        elif format=='int':
            return 1
    
    elif isAtSchool:
        if format=='str':
            return "Josh is at school."
        elif format=='int':
            return 2
    
    else:
        if format=='str':
            return "Don't know where Josh is."
        elif format=='int':
            return 0

# This is ran if being run as a CGI script.
def main():
    import cgi
    form = cgi.FieldStorage()
    format = form.getvalue('fmt') or 'str'
    
    mimetype = 'text/plain'
    if format == 'json': mimetype = 'application/json'

    print "Content-Type: %s\n" % mimetype
    print place(format)

if __name__=='__main__': main()