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  The tips of learning Linux kernel

  As the Linux kernel has become one of the most gigantic and complex software project in the world, its complication scare many novices away. In this post, I will give some personal experience on how to learn Linux kernel, and hope these tips can offer some help to newcomers. (1) Download vanilla kernel and install it. Yes, I suggest you can find a physical machine, or if you really don’t have one at hand, virtual machine is also OK. Download the newest vanilla k...

       2017-07-28 22:53:11

  Data as code

What is a good command line parser API? A good command line parser should consider below 5 aspects: Support convenient help information generation Support sub commands, for example, git has push,pull,commit sub commands. Support single character option, word option, flag option and option with parameter. Support default option, for example, if no -port is set, set it as 5037 Support usage model, for example, tar's -c and -x is mutually exclusive, they belong to different usage models. Here are...

   Command line,API     2013-08-08 22:40:36

  Disgusting programming language list

To avoid arguments among different programming languages, this ranking only covers the opinions from programmers with multi-language experience. Also it doesn't mean the language is not good if the language is on the list, it just means those developers don't like some features of the language. Below ranking is summarized from Quora、Stack Overflow and Hacker News. 10. Python Reason : It uses code indent to define block level scope, why not use curly braces? It also uses massive colons and ...

   Programming language rank     2013-09-27 09:53:39

  $40 million per year to keep Wikipedia running

Wikipedia is an incredibly frugal and efficient nonprofit organization. It serves half a billion visits per month. But do you know how much it costs to keep this huge website running? According to 2012-13 Wikimedia Foundation Annual Plan, the expected spending is around $40 million. Some may argue that Wikipedia is just a site with "just text", why does it cost so much? Oliver Emberton shared his view. To keep Wikipedia running and serve 500 million visits per month. First, you're going to need ...

   Wikipedia,Spending,Cost     2013-09-24 23:05:10

  Convert HTML to DOM elements using JavaScript

In some cases, one would want to convert a HTML string to the DOM elements so that JavaScript can handle them easily. This is frequently used when one get some data from third party APIs where the data is in HTML format. In JavaScript, there are a couple of ways one can use to convert HTML to DOM elements. DOMParser document.createElement DOMParser DOMParser can parse XML or HTML source stored in a string into a DOM Document. After the conversion, the normal JavaScript call of h...

   JAVASCRIPT,DOMPARSER,DOCUMENT.CREATEELEMENT,HTML,DOM     2017-08-18 22:51:46

  How to optimize MySQL insert statement

For a big data system, one problem is the data access efficiency, one more problem is that the data insertion is very slow. We had a service system, the data loading process would take 4-5 hours. This time consuming operation is risky since if the program is interrupted during the loading process, it might be rerun, this will be troublesome. So it's necessary to improve the insertion efficiency for big data systems. Here we provide two optimization suggestions. 1. Combine multiple insert stateme...

   MySQL,insert,optimization     2012-10-24 22:03:13

  The Pitfall of WebSocket Disconnections Caused by Browser Power-Saving Mechanisms

Preface Recently, while using WebSocket (WS) connections, we encountered frequent disconnection issues, occurring hundreds of times per day for a single user. Although using the auto-reconnect feature of socket.io allowed us to quickly restore connections after disconnections, it did not guarantee that every reconnection would successfully receive WS messages. Therefore, we conducted several investigations and tests. Ultimately, we identified the root cause of the issue: the browser's power-savi...

   WEBSOCKET,JAVASCRIPT,POWER SAVING,TROUBLESHOOTING     2024-06-23 01:19:39

  Generate certificate from cert file in Java

A certificate is often used to prove the identity of a server. The certificate will contain information such as the subject and issuer of the certificate. It will also contain the validation date of the certificate. A certificate is often exported to an external cert file which is transferred over the internet. We will often see its use in SSL communication which provides secure communication between two entities. In this post, we will show how to read the data from an external certificate file ...

   PKCS12,CertificateFactory,Example,Java,X509     2015-06-08 06:47:05

  Stub Mixlib::ShellOut and shell_out in Ruby unit testing

Unit testing is part of software development to ensure the tiny component of a function can work as designed. Different frameworks and tools can be used to run unit testing for different programming languages. In Ruby, one popular unit testing framework is Rspec, or Chefspec if you are writing Chef recipes. While writing Chef recipes, some low level commands(DOS commands or shell commands) need to be executed on the managed resource to perform actions or gather information. For example, lis...

   RUBY,UNIT TESTING,RSPEC,CHEFSPEC,SHELL_OUT     2016-11-11 00:14:46

  Different types of keystore in Java -- PKCS12

PKCS12 is an active file format for storing cryptography objects as a single file. It can be used to store secret key, private key and certificate.It is a standardized format published by RSA Laboratories which means it can be used not only in Java but also in other libraries in C, C++ or C# etc. This file format is frequently used to import and export entries from or to other keystore types. Next we will explain the operations which can be performed on PKCS12 keystore. Create PKCS12 keystore Be...

   Java, PKCS12, keystore, tutorial     2015-01-04 21:08:49