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  Writing robust shellling scripts

Many people hack together shell scripts quickly to do simple tasks, but these soon take on a life of their own. Unfortunately shell scripts are full of subtle effects which result in scripts failing in unusual ways. It's possible to write scripts which minimise these problems. In this article, I explain several techniques for writing robust bash scripts. Use set -u ...

   Robust,Shell script,Set,Commands     2012-03-19 13:25:26

  Understanding an interesting JavaScript map function question

With the evolvement of JavaScript, lots of new features have been added this old but robust language.  Among them are lots of functional programming language related functions like map, filter, each etc. In this post, we will cover one function map and its interesting behavior. Before dive into the details, let first take an example, do you know the output of below function call? ['1', '7', '11'].map(parseInt) You may think that it's easy and the output would be [1, 7, 11] Can you try to ru...

   JAVASCRIPT,MAP,FUNCTIONAL PROGRAMMING     2019-06-14 08:34:46

  Gcd Algorithm with JavaScript

How to find the greatest common divisor between two integers? We may encounter this problem frequently in interviews or other occasions. An efficient metho to find gcd is the Euclidean algorithm, which uses the division algorithm in combination with the observation that the gcd of two numbers also divides their difference: divide 48 by 18 to get a quotient of 2 and a remainder of 12. Then divide 18 by 12 to get a quotient of 1 and a remainder of 6. Then divide 12 by 6 to get...

   JavaScript,Algorithm,Gcd,Implementation,     2011-09-21 15:57:32

  bash network interface

Some of us may have seen /dev/tcp/<host>/<port> before, is this a special file system implemented in some BSD kernel? Because there is no /dev/tcp in Linux. Actually, this one is implemented in bash. We no need to rely on wget,nc to do network connection. It's very easy to use this interface: bash-4.2$ cat </dev/tcp/time.nist.gov/13 56188 12-09-18 15:34:26 50 0 0 733.5 UTC(NIST) * bash-4.2$ exec 3<>/dev/tcp/www.w3.org/80 bash-4.2$ echo -e "GET / HTTP/1.0\n\n" >&3 b...

   Bash,Network interface,/dev/tcp     2013-07-20 00:57:52

   Python – parallelizing CPU-bound tasks with multiprocessing

In a previous post on Python threads, I briefly mentioned that threads are unsuitable for CPU-bound tasks, and multiprocessing should be used instead. Here I want to demonstrate this with benchmark numbers, also showing that creating multiple processes in Python is just as simple as creating multiple threads. First, let’s pick a simple computation to use for the benchmarking. I don’t want it to be completely artificial, so I’ll use a dumbed-down version of factorization...

   Python,Multitasking,Multiprocessing,CPU bound     2012-01-17 11:38:22

  Creativity requires isolation

How many times have you tried to get something done that needed some touch of originality and creativity and yet got that annoying mind block which is manifested by blank stares, scratching and biting on anything in reach? “all the damn time” I hear? As preconditions to be creative, one should know something well while having the utmost focus on it. Someone who knows little about aerodynamics can’t come up with the idea for next concord. And focus has two aspects: kno...

   Creativity,Isolation,Quiet,Paper,Pen     2011-11-28 09:33:57

  Avoiding and exploiting JavaScript's warts

One's sentiment toward JavaScript flips between elegance and disgust without transiting intermediate states. The key to seeing JavaScript as elegant is understanding its warts, and knowing how to avoid, work around or even exploit them. I adopted this avoid/fix/exploit approach after reading Doug Crockford's JavaScript: The Good Parts: Doug has a slightly different and more elaborate take on the bad parts and awful parts, so I'm sharing my perspective on the four issues that ha...

   JavaScript,warts,Exploit,with,variable,this     2012-02-15 05:51:21

  Paradigms of Iteration in JavaScript

One of the joys of programming is that no matter how simple a problem may seem there are always tons of ways to solve it. It can be good practice to go back and revisit fundamentals by solving simple problems with as many implementations as you can think of. In this post we'll explore approaches to basic iteration in JavaScript. This style of exercise is a good interviewing technique, too, because it's open ended and leads to good discussions. The focus isn't a tricky, wacky problem you're...

   JavaScript,Iteration,Wrap,Recursive,For,Loop     2012-01-08 10:11:15

  Why Building a Mobile App is Hard

Kent Nguyen has a great article about how building iOS apps takes a lot of work. And, here at Parse, we agree. Making a well-designed app is not a trivial task. Many non-developers hugely underestimate the amount of sweat and tears that goes into a single app. The big component that is overlooked and that Kent stresses is the server component. An app is not an island. Users expect their apps to richly interact with the internet. This means you need to worry about developing code on servers, com...

   Mobile app,Hard,Chanllenges,Platform     2012-02-01 04:45:45

  20 bit operations programmers should know

While talking about bit operation, programmers usually think about its efficiency. In embedded programming and system core optimization, appropriate use of bit operations is always a fascinating. When finding a job, it will help you a lot if you use bit operations when writing codes. Mastering simple bit arithmetic skills is necessary. 1. Get maximum int value int getMaxInt(){           return (1 << 31) - 1;//...

   Bit operation, Tips     2012-12-19 12:53:33

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