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I was reading about vim the other day and found out why it used `hjkl` keys as arrow keys. When Bill Joy created the vi text editor he used the ADM-3A terminal, which had the arrows on hjkl keys. Naturally he reused the same keys and the rest is history. Here is how the `hjkl` keys looked. ADM-3A keyboard's hjkl…
A couple of days ago I watched a How Computers Learn talk by Peter Norvig. In this talk, Peter talked about how Google did machine learning and at one point he mentioned that at Google they also applied machine learning to hiring. He said that one thing that was surprising to him was that being a winner at…
I recently learned an interesting fact about Fibonacci numbers while watching a random number theory video on YouTube. Fibonacci numbers can be used to approximately convert from miles to kilometers and back. Here is how. Take two consecutive Fibonacci numbers, for example 5 and 8. And you're done converting. No...
I decided to write an article about a thing that is second nature to embedded systems programmers – low level bit hacks. Bit hacks are ingenious little programming tricks that manipulate integers in a smart and efficient manner. Instead of performing operations (such as counting the number of 1 bits in an integer)…
At Browserling we are huge open-source fans and we have open-sourced 90 node.js modules! That's right! 90 node.js modules. All written from scratch. We're crazy! Edit: Now we've open-sourced several hundred! Here is the complete list of all the modules together with their brief descriptions. We have published all…
I thought I'd share my favorite regex of all time. [ -~] Any idea what this regexp matches? Scroll down for the answer. . . . . . . . . It matches all ASCII characters from the space to tilde. What are these characters? These are all printable characters! Take a look at this ASCII table. Printable characters start…
I was recently interviewed by Fog Creek and one of the questions was about my favorite programming, coding and development books. I got very excited by this question as I'm a huge book nerd. I love books about computers, programming, and science. Every few months I spend a day or two researching the latest…
A couple of days ago I watched a How Computers Learn talk by Peter Norvig. In this talk, Peter talked about how Google did machine learning and at one point he mentioned that at Google they also applied machine learning to hiring. He said that one thing that was surprising to him was that being a winner at…
Hi everyone! Here's part three of my favorite programming, computer, and science books. If you're just joining, please see part one and part two for introduction. This time I'll be sharing my favorite books about Unix, logic programming, thermodynamics, and mathematical foundations of computer science. In one of the...
Hi everyone! Here's part five of my favorite programming, computer and science books. If you're just joining, please see part one, part two, part three and part four. I've been collecting and researching science, math, physics, programming books since 2001 or 2002, so it's been close to 15 years of book research…
Many people are surprised to learn that `sed`, a seemingly simple text filtering program, is actually Turing complete. This realization prompts the question: how can a text processing utility achieve such computational power? The answer lies in sed's fundamental operations. Essentially, sed functions as a miniature...
I love working in the shell. Mastery of shell lets you get things done in seconds, rather than minutes or hours, if you chose to write a program instead. In this article I'd like to explain the top one-liners from the commandlinefu.com. It's a user-driven website where people get to choose the best and most useful...
Here's something you didn't know about bash functions. Usually when you write a function you do this: function name () { ... } Right? I know you do, because that's how everyone writes functions. Well, here's the thing. In bash { ... } doesn't mean "function's body" or "function's scope" as in JavaScript or C. It's...
As you all may know, I watched and posted my lecture notes of the whole MIT Introduction to Algorithms course. In this post I want to summarize all the topics that were covered in the lectures and point out some of the most interesting things in them. Actually, before I wrote this article, I had started writing an...
You have probably all heard the following story about Jobs meeting Knuth for the first time in 1983. Steve had managed to get Don Knuth, the legendary Stanford professor of computer science, to give a lunchtime lecture to the Mac team. Knuth is the author of at least a dozen books, including the massive and somewhat...
I recently learned an interesting fact about Fibonacci numbers while watching a random number theory video on YouTube. Fibonacci numbers can be used to approximately convert from miles to kilometers and back. Here is how. Take two consecutive Fibonacci numbers, for example 5 and 8. And you're done converting. No...
Frameworks are one of the hugest anti-patterns in software development. They're hard to learn. They limit your creativity. They increase your project's complexity and dependencies. They go out of business and get abandoned. You have to maintain and upgrade your code to match the latest framework versions for no good...
This is the fifth part of the Bash One-Liners Explained article series. In this part I'll teach you how to quickly navigate around the command line in bash using emacs-style keyboard shortcuts. That's right, emacs-style keyboard shortcuts. It might surprise you but by default bash uses emacs-style keyboard shortcuts...
sed book This is the world's best introduction to sed - the superman of UNIX stream editing. Originally I wrote this introduction for my second e-book, however later I decided to make it a part of the free e-book preview and republish it here as this article. Introduction to sed Mastering sed can be reduced to...
Take a look at this Perl regular expression: perl -lne '(1x$_) =~ /^(11+?)\1+$/ && print "$_ is composite"' This regular expression matches only the composite numbers (and doesn't match prime numbers). Can you figure out how it works? I'll give the explanation below but try to figure it…
As you all may know, I watched and posted my lecture notes of the whole MIT Introduction to Algorithms course. In this post I want to summarize all the topics that were covered in the lectures and point out some of the most interesting things in them. Actually, before I wrote this article, I had started writing an...
This is just amazing. In 20 lines of node.js code and 10 minutes of time I was able to write a HTTP proxy. Take a look: var http = require('http'); http.createServer(function(request, response) { var proxy = http.createClient(80, request.headers['host']) var proxy_request =...
I was just watching a friend of mine work with git, and he'd always type all the git commands in full, like git status and git push. I realized that he must not be the only one to do so, so I decided to write this quick blog post and encourage everyone to create Huffman coded aliases for the most commonly used...
I just had my minute of fame! I was just interviewed by Fog Creek on their development blog. Fog Creek is Joel Spolsky's company. We talked about how I got into software development, what I currently do, my current setup and my favorite books. I've been a lifetime fan of Fog Creek Software and it just feels so great…
Buy it now for just $19.99 Hello everyone! I have awesome news – I just wrote my first e-book ever. It's called Awk One-Liners Explained and it's based on the Awk One-Liners Explained article series that I wrote here on my blog a few years ago and that has been read over 2,000,000 times. I went through all the...
A while ago I had an on-site job interview at Google. The position I was interviewing for was a Google SRE. SRE stands for Site Reliability Engineering. Site reliability engineers (SREs) are both software engineers and systems administrators, responsible for Google's production services end-to-end. I interviewed…
I love Perl because of its expressiveness. You can write incredible code and it feels just so natural compared to other languages. Here are 8 secret Perl operators that I often use. Only one of them is a real operator (first one). The others are syntactic tricks that make them look like operators but they are not…
Hey everyone, I just pushed 30 of my projects to GitHub. I realized that all the projects were scattered across my blog and there was no central repository. So I took time to organize them, write documentation, and uploaded them to GitHub. I did all of these projects for fun and to learn better programming. You…