Fledgling Polymath

I work in Terminal.app a lot. And one of the things I regularly do is launch a long running task and then go off to do something else (like surf the net or sword flighting)

But I was looking for a way for Terminal to notify me when a long running task has finished. Google and ye shall receive:

alias beep="echo -ne '\007'" # Beep after long running tasks beep_if_long_time_past() { LAST_COMMAND_DURATION=$(($(date +%s) - ${LAST_COMMAND_TIME})) [[ ${LAST_COMMAND_DURATION} -gt 60 ]] && { echo "Last command took ${LAST_COMMAND_DURATION} seconds!"; beep; } export LAST_COMMAND_TIME= } export PROMPT_COMMAND=beep_if_long_time_past trap '[ -z ${LAST_COMMAND_TIME} ] && export LAST_COMMAND_TIME=$(date +%s)' DEBUG

Adding this will send the 'bell' character to the Terminal, even through SSH and screen. The last part of the puzzle is modifying the Terminal.app settings.

I recently wrote a script that I wanted to save the data on exit, and then read it in again. This is pretty trivial to do - use pickle everyone said. And I did.

But then I realised that I might want to quickly edit this data and restart the script. Using pickle makes this a bit more difficult - I would have to import the pickle file into a python shell, make the edit and save it again. What I really want to be able to do is edit the file directly... enter JSON.

So JSON needs no introduction, but that is a little frustrating about it is that there is no timestamp support. I found this out pretty quickly by running a simple json.dumps(my_dict) on my data and getting the following error:

TypeError: datetime is not JSON serializable

So after a quick Google search it turns out the standard JSON library in Python supports custom encoding and decoding. Simple I thought... but then I spent the next hour trawling through different implementation of what I wanted and no advise on what was best.

So I did what any good Python programmer would do - get all the possible solutions from the net, pretty them up and run them through timeit.

We use small ALIX PCs for our field computers. Sure they are old and expensive compared to RaspberryPi and other smaller ARM based computers on the market now, but having x86 compatibility makes things easier for us. The following is everything I needed to install Oracle instant client and cx_Oracle on the Voyage Linux distributions.

First you need to make sure you have the following installed:

python

python-dev

python-setuptools

gcc

libaio1

unzip

If you are missing any of these you can install them using "sudo apt-get install <pkg_name>"

Next, download the instantclient source packages from Oracle's website. Here for x86 and here for x86-64. You will need a free Oracle account to download the files.

Then unzip the two instantclient*.zip files using "unzip instantclient*.zip"

Copy the files into the directory you choose. I chose /usr/local/oracle so: "mkdir /usr/local/oracle; mv instantclient_11_2 /usr/local/oracle/"

In the past I've found I need to make a symlink to one of the libraries libclntsh. "cd /usr/local/oracle/instantclient_11_2; ln -s libclnths.so.11.1 libclntsh.so; cd -"

Now add two environment variables to your /etc/profile or .bashrc:  export ORACLE_HOME:/usr/local/oracle/instantclient_11_2 export LD_LIBRARY_PATH:$ORACLE_HOME

I've been using bottle.py a lot recently to quickly write REST-like APIs. I say 'REST-like' because at the moment they mostly only satisfy GET requests. Up until now actually. Now I want to write a full REST interface with support for GET, POST, PUT and DELETE.

As part of this I need the most basic of basic authentication on my server. I want to put a password on my POST, PUT and DELETE requests. I had a look at bottle-cork but it seemed overkill for what I needed. Digging into the bottle.py source code I found this little gem of a decorator called auth_basic(). So here is how you use it:

import bottle def check(user, passwd): if user == 'ben': return True return False @bottle.route('/') @bottle.auth_basic(check) def index(location): print 'auth', bottle.request.auth print 'remote_addr', bottle.request.remote_addr return "Yay - you made it!" if __name__ == '__main__': print "Starting server" bottle.run(host='0.0.0.0', port=8080, reloader=True)

That is a pretty simple demonstration. If you attempt to go to the page in a browser you will get a 401 Error back. To access the page in python, use this little code snippit from StackOverflow:

import urllib2, base64 (user, password) = ('ben', 'xyz') request = urllib2.Request("http://localhost:8080/") base64string = base64.encodestring('%s:%s' % (username, password)).replace('\n', '') request.add_header("Authorization", "Basic %s" % base64string) result = urllib2.urlopen(request) print result.read() 

And you should see "Yay - you made it" printed out.

So I set myself a little challenge the other day. I'm always using Terminal in Mac OS X and also using ssh pretty extensively and I wanted a way to automatically set the tab name to be the hostname of the server I've connected to. Using a little regex magic (and teaching myself how to use regular expressions again), I came up with the following:

function tabname { printf "\e]1;$1\a"; } function winname { printf "\e]2;$1\a"; } function ssh() { echo "$@" | tabname `sed -E 's/(.*@)?([-a-zA-Z0-9\.]*)(.*)/\2/'`; /usr/bin/ssh "$@"; tabname; }

Insert this into your .bashrc script, restart your Terminal and test it out. The functions are there for changing the tab name and the window name, so feel free to make you own variations for your commonly used apps.

As a small aside, make sure you you have the following in your .bash_profile which will make sure it always runs your .bashrc 

I think the hardest part of setting up a new blog is trying to find something witty and oxymoronic to use as the blog title. That is because no one wants to have the blog called "Bob's Blog" or "Thoughts of Ben" (I once had a blog called this - shame).

Anyway - I was trawling the interwebs one day and came across a polymath - the term used to define "a person whose expertise spans a significant number of different subject areas". Another definition I came across was "a person of great and varied learning". I had the following thoughts:

what a cool word

I have an interest in a huge variety of topics and areas

I am a software engineer by day - working on a variety of projects including embedded microcontrollers, databases, websites, Java, Python, C and the list goes on. Outside of work I'm a swing dancer, a photographer and a traveller. I love my life and my areas of interest - things I'm very very passionate about - and I feel that along the way of my quest to be an expert in these areas I might just have some wisdom to share. Hence why this blog exists.

So that is it. I guess if I succeed in my quest I could almost classify myself as a polymath - until then I'm just a learner like everyone else.

I expect this blog to be a completely random mis-mash of topics, but I also hope that by sharing them with the rest of the world that I might just be able to help people. So to you, the person who is reading this, I hope I was able to solve your question that lead you to be here... and if I didn't I hope you enjoyed a part of the randomness that is my life.