Good bye wordpress.com
Hi, I’m moving to a new home today – ershadk.com. Please update your email subscriptions and feed settings. Thank you very much for reading and sharing your opinions on little posts I wrote and please do that in my new blog too. And I would like to thank wordpress.com for hosting my little blog for last few years. All posts and comments in this blog are copied to the new blog. That’s it, Welcome to ershadk.com!
Tathva memories @ NITC
“.. I’m leaving this campus today. I will miss the late-night hangouts with Kartik and Pankaj.. I will miss the stay in Kartik’s room with Arjun and Rohit (If you are reading this, All the best for your IAS, brother). I will miss Ramnath, Arnab and all my friends here and this great institution.. I’m sure I will be back here for the next event.. With a million beautiful memories in 4 days.. Adieu NITC..”
Anagram Solver in C
Hi, Here’s a small anagram solver written in C. It works based on generating permutations of given string and comparing them using a dictionary. For fast search in dictionary, the program first creates an index of the starting location of each alphabet. It takes a few minutes to process long words.
Here’s the source code. Suggestions are always welcome, Greetings 
Update: There’s a little problem in using the term ‘anagram solver’ here. An anagram solver finds words from another valid word – But this program finds words from the characters of given valid/invalid word. Thanks to technikhil for the info
Why I started loving Archlinux
We like simplicity. We like everything new.
It’s been some years since I switched completely to GNU/Linux. I always wondered at its stability, security, features, community and at the people who use it. GNU/Linux helped me to have exciting computing experience all the time filled with wonders and fun. I forgot about the existence of Antivirus software. Forgot the time I feared autorun.inf and weird executable files. Forgot BSOD and EULA. Now, everything is open. Met many new people, similar interests bonded us. People who use GNU/Linux have always been very helpful. They share knowledge instead of pirated software. They teach us to fish. A kind of special relationship rooted between us, in a world connected by computer networks and its underlying complex abstractions. At this moment, I would like to thank everyone who made lives of people like me colourful.
I had been using Debian Squeeze for a while and was happy with that. Had its complete repo offline which helped me to install any package in spite of the very slow internet connection I had then. Though the things went smooth, I faced some issues during that time with the compilation of new software from source. Fixing dependency issues were pain. The new source of package requires new version of dependencies which were not available in repo. Compiling them from source always created new pains. Updating software/repo was not possible because of the slow speed of internet. Taking laptop to college and updating from there also didn’t work due to various technical and non-technical reasons. I felt like I was completely forbidden from trying new versions of software. I was in a kind of lock then. Suddenly, one fine day, I got a broadband internet connection!
I don’t have words to express how much happiness I felt. Now the scenario has completely changed. I can now change the Debian repo to testing or sid, try new packages, configure backports or update what ever I want. But, I thought it was time for a change. Changes are the spices of life, indeed.
I wanted to install another distro from the mainstream. First, I thought of Fedora 15 which is a very good OS and hacks by Rajeeshettan in it always inspired me. Also I had used Fedora 14 for several months. But in Fedora too, I missed an element of simplicity and playfulness. The point with these type of operating system is that it comes with all basic packages preconfigured and giving us less opportunities to play with those.
Next choice was obviously Archlinux. I have been hearing about it since I met my another GNU/Linux guru – Ashikettan. He blogs about Arch much and talks about it often. Also, I had tried it once months before when I had speedy internet connection. The best thing about Archlinx is that it is a rolling distro, and new packages are always readily available!
To install, I got the 64bit iso image from Arch website and made thumb bootable with abock. The installation went smooth and had a nice time configuring various things along with my favourite desktop environment – KDE. I was not really able to use KDE since the version in Debian Squeeze was a bit buggy and it crashed often. I was using Gnome 2.x then. Now, I’m really happy with KDE 4.7.0 with a distro which can be updated easily using its sweet package manager – pacman. Arch also has a wonderful knowledge base – The ArchWiki. ArchWiki has many tutorials to play with for beginners and for expert users.
To talk about packages in Archlinux, I don’t have words! I remember trying to install new version of Ipython in debian which comes with a new tool called qtconsole. Qtconsole can show the outputs of matplotlib embedded inside the window instead of showing as a pop-up. It was a bit pain fixing various python modules that depended upon on other packages in debian. But in Archlinux, a simple ‘pacman -S ipython’ after a system upgrade with ‘pacman -Syu’ solved the issue. (Please note that though ‘pacman -Sy ipython’ alone installs new version of Ipython, it may lead to dependency issues sometimes. Always install with ‘-S’ and have an system upgrade with ‘-Syu’ often). Upgrading the system obviously updates kernel, now Arch has kernel 3.0 in repo!
Please do not have a feeling that I’m saying other distro/package managers are bad or less useful than Arch/pacman, I was simply having a comparison under special conditions – Indeed, every GNU/Linux thing is great and well developed!
Another great feature I found in Archlinux is the rc.conf file. We can easily configure various system wide things in /etc/rc.conf file, like which all kernel modules to load, which all daemons to run at start, hostname, timezone, network interfaces, gateways and so on. There’s also an application called ‘rc.d’ which is similar to ‘service’ in debian/ubuntu using which we can start various services like sshd, etc. Also, the support in IRC channel (#archlinux @ irc.freenode.net) and in Arch forums are very helpful.
Finally, as a student, I find Archlinux very useful and informative, Also it’s so much of fun using it. I humbly recommend this sweet GNU/Linux distro to everyone who likes to add more spice to their GNU/Linux computing. I just started with Archlinux and hope I could post more about it in future. Thank you so much for reading. Greetings!
It was really a wonderful experience at MES :)
Yesterday, I went to MES College of Engineering to deliver a small talk on programming and free software, it was entirely a new experience for me. A bigger crowd than expected was present. It went fine Thanks to Raghesh sir, Raju sir, S@IT and to friends there
I’m happy to share my little slides. It was created according to numerous suggestions by Raghesh sir. For fun, the presentation was started with a SMS trigger from audience The code for that is like ‘get-thing-done’ and doesn’t have the quality to upload. It’s developed using python with gammu module. Please feel free to tell me if you want to have a look at the code.
Attribution: ‘Input -> Fun -> Output’ is an idea got from Niyam Bhushan during his talk at NIT Calicut on FOSS Meet day.
Thank you
A cryptographic tool that converts weak password into a strong password before encrypting
Here’s a small encryption/decryption tool that works based on AES algorithm. No matter how weak your password is, the program converts it to a 32 digits hexadecimal number before encrypting. This is achieved by finding the MD5 hash of the password using hashlib python module. This hash is used to encrypt the file.
The idea in my mind while writing this program was this:
Suppose a cracker gets an encrypted file and he figures out it’s encrypted using AES somehow. Then he starts brute force attack on it to find the key and extract information. If the password used to encrypt that file is weak and if it’s based on a dictionary word, the cracker can easily figure out the password. Hence the password given by the user must be made stronger by the encrypting program. And the best way to make a password strong is by using digest algorithms since it’s unique to a string.
What do you think? Am I wrong? Thank you
A small and simple note taking app
Wrote a small python script that can be used with your favorite text editor as a simple note taking application. Hope you like it, suggestions are always welcome
Thank you
C program to extract email IDs from a file
Here’s a small program to extract email IDs from an input file. It could have done using regex (in Python or in any other high level language), but doing it in C is more fun, eh?
The code is here!
Usage: parseEmail [FILE]
Suggestions and improvements are always welcome Thank you!
Setting up a Debian repo in LAN
It was really a nice experience going to MES College Of Engineering, Kuttippuram last week to attend Debian Mini Conf 2011. Met friends, made new friendships and learned many new things from there. Thanks to Jishnu ettan, for giving me a 50GB Debian repo that contains all the packages of squeeze of both i686 and amd64 architectures. Today, I will explain how to set up a Debian repo (squeeze) so that it be can shared over LAN.
First, run terminal and switch to root user.
$su
If you have the repo as an ISO image file, we need to mount it to a directory. The following command does that:
#mount <path-to-iso> <path-to-mount> -o loop
Edit /etc/apt/source.lst and add the repo we mounted. Append the following line to the file:
deb file:///<mounted-path> squeeze main
Update the package list:
#apt-get update
We are going to share the files using http, hence we need a webserver. To install apache:
#apt-get install apache2
Make a symbolic link of <mounted-path> in /var/www
#ln -s /var/www/repo <mounted-path>
Done! Now add this machine as a repository in other Debian systems in LAN, edit /etc/apt/source.lst to:
deb http://<ip-of-server>/repo squeeze main
The same can be done using a FTP server. All you have to do is to make the symbolic link in FTP’s configured path and use ftp:// instead of http:// in /etc/apt/source.lst. Thank you
A sudoku checking program in C :)
It just started when my younger bro, Shafeeq who reads hacker news everyday, found a little interesting blog post. It was about the authors experience in applying for an internship at Google. The candidate was asked to write a program to check a completed sudoku during the telephone interview for errors, in his favorite programming language. I asked bro, “Why don’t you give it a try?!”. He’s now in 11th standard and started coding in C++ which he learns in Computer Science subject. He came up with the code in one day, and then it was my turn to do that Here’s the way I solved the problem and it’s in pure C.
You can find the code here, in github. The input is given as a plain text file that contains 9×9 numbers separated by space. A sample input is given below:
7 2 3 8 4 6 1 5 9
6 1 5 3 9 2 4 7 8
8 4 9 7 1 5 6 3 2
3 7 8 6 5 4 9 2 1
1 9 4 2 8 7 3 6 5
2 5 6 9 3 1 8 4 7
5 6 1 4 7 9 2 8 3
4 8 7 1 2 3 5 9 6
9 3 2 5 6 8 7 1 4
And to check for errors, please call the program with the file as argument, like this -
$checksudoku <data_file>
Hope you enjoyed it, Please go through the code and feel free to post your valuable comments and suggestions here. Thank you
