Saturday, 22 September 2012

What I like about my 2002 Volvo S40 SE 2.0 Auto

Ok, so, for a completely off-topic post about a car. I bought a 2002 Volvo S40 SE 2.0 Automatic a few weeks ago for family day trips etc and not commuting. So I wanted something cheap, comfortable and safe. This car seems to pretty much fit exactly, so much so that I thought I'd share some of the things I like about it. Perhaps you are in a similar situation and are considering buying a second-hand Volvo.


For long day trips or weekends away this is quite important. Bouncing down the motorway in a old Fiesta isn't exactly comfortable. So, what does my car give me?

  • Climate control - Not just aircon, but proper climate control. Set it to AUTO, choose a temp and voila.
  • Automatic - Not to everyone's taste, but I'm kinda liking it. Makes traffic jams bearable.
  • Cruise control - Haven't used it yet, but nice idea for those long motorway journeys.
  • Heated front seats - Still too warm for them, but I think they'll come in handy in the winter :)
  • Adjustable dashboard light brightness - Nice little touch.
  • CD and tape player - CD player is a requirement, and the tape player is even handy for playing mp3s or Spotify from my phone.
  • 2.0 Engine - Car is pretty responsive.
  • Heated door mirrors - Again, too warm to have used them yet, but will come in handy later.


The most important thing as a family man is of course safety.

  • Side markers - Little orange lights on the sides of the car at the front and back to help visibility of the car from the side. Required in North America but not in Europe, I didn't see a single other car last night with them whilst walking in town.
  • Headlight wipers - Not only do they look kinda cool, but sort of handy.
  • Driver and passenger airbags - The basics.
  • Side impact cushions - A nice extra little touch, adding to safety.
  • 4 star Euro NCAP rating - "The S40 was awarded four stars for protection in frontal and side impacts, the only one of 13 family cars tested to achieve this result"

Family Friendly

The idea was to get a car that was big enough for day trips without being too big for the terrible on road parking where I live.
  • Parking voucher clip - Silly, but very cool. A little clip on the right of the windscreen to place parking vouchers etc. Handy, really handy and a nice little touch.
  • Boot size - 415 litres, big enough to put the pram base in without taking off the wheels.
  • Lots of random storage - Little storage spaces throughout the car.
  • Cup holders in central arm rest - Another nice little touch.
  • Full electric windows with driver-side control - All four door windows are electric.
  • Leather seats - Easy to clean and spill friendly, perfect for kids in the back.

Finally, and not in any particular category, awesome advice from the excellent community at

Sunday, 19 August 2012

Visualisation with Scratch

Scratch allows you to create interactive stories, games, music and art using drag-and-drop programming. It is an excellent way to introduce basic programming concepts, such as variables and loops. But, it is also quite powerful, as it supports bi-directional communication to such things as Lego Mindstorms, and more generally, using TCP/IP. I decided to see what sort of data visualisation I could achieve with a few spare minutes and a bit of python code.

The first attempt ended up as a sort of "meme cloud". Here, you send Scratch an alert level and a message, and it will display a meme based on the level, with the message in a speech bubble.The levels are:

The most recent alert is shown with no transparency and with the speech bubble. As the alerts get older, they become increasingly transparent. Positions of the memes are random. It currently only supports 10 sprites, which means it will show up to 10 memes at any one time.

Here is a section of the code for one of the sprites:

The problem with this approach is that Scratch doesn't allow you to dynamically create sprites, which sort of limits the functionality for certain things. However, there is an alternative. A sprite has, amongst all sorts of things, a pen. This pen can have colour, thickness, shade etc. Moving the sprite while the pen is "down" basically just draws on the screen. So, although we can't dynamically create sprites, we can draw all sorts of things programmatically. This takes us to attempt number two.

The plan here was to draw some sort of time chart or graph. A python script sends Scratch a pen size and colour for every event, and Scratch draws this. As it receives events, the pen moves to the right to create a sort of time chart. If the pen gets to the end of a line, it drops down to a new line. If it gets to the bottom of the screen, it goes back to the starting position in to top left corner. This means you can see the details of a relatively large number of events on a single screen, in order of time.

The example video below just uses random colours and pen sizes, so you won't be able to see any patterns. However, with real data you should be able to see correlations such as spikes in the number of errors, or outages etc. Also, the time between events in the video is fixed, so it looks a little boring. The white square shows the current position.

Not bad for a bit of dragging-and-dropping, and some python. I'll leave it as an exercise for the reader to integrate it into something like Splunk or Nagios :)

You can download the meme cloud python here, and the meme cloud scratch file here. The line viz python can be downloaded here, the scratch file here.

Wednesday, 18 January 2012

Passphrase generator in bash


The script below has been improved upon and can be found here:

Passwords are dead. Long live passphrases. Or something like that anyway. As perfectly summarized by XKCD here, passwords are hard to remember and easy to guess. Passphrases on the other hand are easy to remember and hard to guess.
To help generate passphrases, I've put together a little bash script.
Firstly, download the dictionary containing 10000 most common English words. If you have a 4 word passphrase, thats 10^16 possible combinations.
$ wget
Now save the following script:


chars="a-zA-Z0-9 "
size=$(cat $dict | wc -l)
echo "#!/bin/bash" > $script
( echo -n "dict=( "; i=0; cat $dict | while read word; do echo -n "$word " | tr -c -d "$chars"; if [ "$i" -eq "10" ]; then i=1; echo ""; fi; ((i++)); done; echo ")" ) >> $script

echo "size=$size" >> $script
echo 'count=${1:-10}

for i in $(seq 1 $count); do
    for j in $(seq 1 $words); do
        let "r %= $size"
        if [ "$first" == "0" ]; then
            echo -n " "
        echo -n "$word"
    echo ""
' >> $script
chmod +x $script
Using modulo on a random number? tut tut tut. Anyway, I've called this script
Now run it, giving it the dictionary file and an output script name:
$ ./ top10000en.txt
What it basically does is embed an array of words into plus the code necessary to show passphrases.
It will look something like:
dict=( the of to and a in for is The that on 
said with be was by as are at from 
it has an have will or its he not 
were which this but can more his been would 
definite fragile rewards antiabortion respects careers backers seize inefficient 
conceptual densities EPS Me Sparc spirits experimentally shallow )

for i in $(seq 1 $count); do
    for j in $(seq 1 $words); do
        let "r %= $size"
        if [ "$first" == "0" ]; then
            echo -n " "
        echo -n "$word"
    echo ""
We can now run it:
$ ./ 
Does Brazil quotas message
amount losers sing Oregon
patient misleading rebels smoking
refuse subordinated clerk wrote
have handle Rockwell strong
Committee Insurance consumer else
tariffs Unit mouth loved
V singled graduate kidney
uranium Hungary scientists Mar
fined Hercules Kemp Indian
Or, if we wanted to create just one 5 word phrase:
$ ./ 1 5
Commodity dioxide Boris unit drop

Thursday, 12 January 2012

Visualising rules from Firewall Builder - Part 1

Firewall Builder (available here is a GUI that lets you configure a variety of firewall devices, for example iptables on a linux box or Cisco ASAs.

The idea is to take the configuration file from Firewall Builder and generate some sort of rule visualisation. The ruleset I'm using is basically just the built-in template called "fw template 3". I then saved the ruleset as testfw.fwb.

So, lets process the file:

user@host:~/fwbvis$ ./ testfw.fwb ignoreme

Where the arguments are as follows:

  • - the script (below)
  • testfw.fwb - the firewall config saved by Firewall Builder
  • ignoreme - to be ignored for now. It will become a configuration file for colours etc.
  • - the output file. We just generate a png at the moment, in this case called

Here is the result:

It isn't perfect, but it is a pretty good start. The colours are as follows:

  • red - reject
  • orange - deny
  • green - accept
  • blue - anything else

So, here is the script so far. It's pretty ugly btw...


import sys
import pydot
from xml.etree.ElementTree import ElementTree

sFWFile = sys.argv[1];
sConfigFile = sys.argv[2];
sOutputFile = sys.argv[3];

    ds = open(sFWFile)
    print "Could not open file", sFWFile

    tree = ElementTree()
    print "Could not parse file", sFWFile

graph = pydot.Dot(graph_type='digraph')

prefix = ""
rules = []
objects = {}
for element in tree.iter():
    tag = element.tag
    if tag[0] == "{":
        uri,tag = tag[1:].split("}")
        if prefix == "":
            prefix = uri
    oid = element.get('id')
    if oid is None:
    objects[oid] = {'tag': tag }
    for (key,value) in element.items():
        if key != 'id':
            objects[oid][key] = value

for rule in tree.findall('.//{%s}PolicyRule' % prefix):
    oid = rule.get('id')
    action = objects[oid]['action']
    color = "black"
    if action == "Reject":
        color = "red"
    elif action == "Deny":
        color = "orange"
    elif action == "Accept":
        color = "green"
        color = "blue"

    src = rule.find('.//{%s}Src' % prefix).find('.//{%s}ObjectRef' % prefix).get("ref")
    if src in objects:
        src = objects[src]['name']
    dst = rule.find('.//{%s}Dst' % prefix).find('.//{%s}ObjectRef' % prefix).get("ref")
    if dst in objects:
        dst = objects[dst]['name']
    srv = rule.find('.//{%s}Srv' % prefix).find('.//{%s}ServiceRef' % prefix).get("ref")
    if srv in objects:
        srv = objects[srv]['name']
        srv = "unknown"
    graph.add_edge(pydot.Edge(src, dst, label=srv, color=color))


So, there you have it. More to follow as things improve.

Sunday, 1 January 2012

Some bash array functions

Following on from the previous post, here are some functions for bash arrays. I'll add to this post later with more functions.
Test if a variable is an array:
# is_array - Tests whether variable name is an array
# Parameters:
#   name - name of variable to test
# Returns:
#   0 if an array
#   1 otherwise
    # Only takes one argument
    if [ "${#}" -ne "1" ]; then
        return 1

    # Name of the variable to test
    local name="$1"; shift
    # Run the declare command against the variable
    local x=$(declare -p $name 2>/dev/null)
    # If it errored then the name probably isn't even
    # a variable
    if [ "$?" -ne "0" ]; then
        return 1
        # It is at least declared, test if it is an array
        if [ "${x:8:2}" == "-a" ]; then
            return 0
            return 1
Push values onto an array:
# array_push - Pushes one or more values onto an array
# Parameters:
#   name - name of the destination array
#   ...  - values to push onto array
# Returns:
#   Nothing
    # Need two or more arguments
    if [ "${#}" -lt "2" ]; then

    # Name of the destination array
    local name="$1"; shift
    # Number of elements we're going to push
    local numElements=${#}
    # Counter
    local i=0
    # Starting position of destination array is the
    # size of the array
    eval local start=\$\{\#$name\[\@\]\}
    # Iterate over the elements supplied, adding them
    # to the destination array
    while [ "$i" -lt "$numElements" ]; do
        eval $name\[$pos\]=\"$1\";
Pop from an array:
# array_pop - pops a value from the end of the array
# Parameters:
#   name - name of array
#   dest - optional name of variable to put value in
# Returns:
#   Nothing
    # Need at least one argument
    if [ "${#}" -eq "0" ]; then

    # Name of the array
    local name="$1"; shift
    # If we have a second argument, use it to write value
    if [ -n "$1" ]; then
        local dest="$1"; shift
        local dest=""
    # Size of the array
    eval local numElements=\$\{\#$name\[\@\]\}
    # Index of element is one less than size
    local index=$((numElements-1))
    # Get the value
    eval local value=\"\$\{$name\[$index\]\}\"
    if [ -n "$dest" ]; then
        # Update the specified dest variable
        eval $dest=\"$value\"
        # Simply echo the value
        echo "$value"
    # Unset from the array
    eval unset $name\[$index\]
One thing to note is the clash between variable names. E.g. if you wanted to return the value into the name variable, it would be bad to call that variable 'value'. local doesn't help here, best option would probably to use obscure variable names that are unlikely to clash.
Walk an array:
# array_walk - Walks through an array, calling the
#              callback function for each element
# Parameters:
#   name     - name of array to walk
#   callback - name of callback function
#   ...      - any parameters to be passed to callback
# Returns:
#   Nothing
    # Name of array to walk over
    local name="$1"; shift
    # Name of call back function
    local callback="$1"; shift
    # TODO - We should probably check whether callback
    # is actually a function

    # Number of elements in array
    eval local numElements=\$\{\#$name\[\@\]\}
    # Counter
    local i=0
    # Iterate over the elements in the array
    while [ "$i" -lt "$numElements" ]; do
        # Get the value
        eval value=$\{$name\[$i\]\}
        # Check whether it is an array
        is_array $value
        if [ "$?" -eq "0" ]; then
            # If so, recursively walk that array
            array_walk "$value" "$callback" "$@"
            # Just a variable, so call the callback
            # function giving it the args and value
            $callback "$@" "$value"
Now, a little play with those functions:
declare -a aTest

echo First push
array_push aTest 'Hello' 'there' 'you' ':)'
echo new array is ${aTest[@]}

declare -a aTest2
echo Second push
array_push aTest2 'How' 'are' 'you today?'
echo second array is ${aTest2[@]}

echo Third push to add second array to the first
array_push aTest 'aTest2'
echo first array is ${aTest[@]}

echo Defining destination array
declare -a aMerged
echo defining callback function
    local name="$1"
    local value="$2"
    # Simple push the value onto the destination
    array_push "$name" "$value"
echo Doing walk
array_walk aTest merge aMerged
echo merged array is ${aMerged[@]}

echo Popping last element of merged array by reference
array_pop aMerged val
echo Value is $val
echo and again
array_pop aMerged val
echo Value is $val
echo merged array is now ${aMerged[@]}
Running it gives us:
$ ./ 
First push
new array is Hello there you :)

Second push
second array is How are you today?

Third push to add second array to the first
first array is Hello there you :) aTest2

Defining destination array
defining callback function
Doing walk
merged array is Hello there you :) How are you today?

Popping last element of merged array by reference
Value is you today?
and again
Value is are
merged array is now Hello there you :) How
So that sort of works. Next I should add an array_indexes() and array_values(). Oh, and happy new year :D
Added array_pop function.