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  gethostbyname vs getaddrinfo

getaddrinfo is slower than ping when resolving domain names. I think ping uses gethostbyname to resolve a domain name. The question becomes whether getaddrinfo is slower than gethostbyname. After testing with both functions, we find that getaddrinfo is really slow compared to gethostbyname. By strace tracking,  we find getaddrinfo will communicate with DNS server 10 times and gethostbyname will communicate with DNS server communication twice.gethostbyname is an old way to resolve domain nam...

   C++,network,DNS     2012-08-15 14:06:34

  Differences between bashrc and profile in Linux

After login to a Linux system, the command console will show up with a prompt label such as # or ~, a shell command can be typed after this prompt and the system can execute the command thereafter. All these operations are handled by shell. Shell is a command language interpreter that executes commands read from the standard input device (keyboard) or from a file. There are different types of shells such as bash, ksh, csh etc. The most commonly used of them is bash and it's also the de...

   LINUX,PROFILE,BASH,BASHRC,.BASHRC,.PROFILE     2016-11-05 22:17:51

  Why I Still Use Emacs

At school, I’m known as the Emacs guy; when people have questions about configuring Emacs or making it work a certain way, they often come and ask me. Sometimes, some people ask me why use Emacs at all? Isn’t it a really old editor and aren’t Eclipse or Visual Studio much better? I mean, they don’t have weird key bindings and have intellisense, that’s surely better for a programmer, right? I will attempt in this post to explain some of the reasons why I still c...

   Linux,Emacs,Editor,Advantage,IDE     2012-02-20 05:30:41

  How Integers Should Work (In Systems Programming Languages)

My last post outlined some of the possibilities for integer semantics in programming languages, and asked which option was correct. This post contains my answers. Just to be clear: I want practical solutions, but I’m not very interested by historical issues or backwards compatibility with any existing language, and particularly not with C and C++. We’ll start with: Premise 1: Operations on default integer types return the mathematically correct result or else trap. This is th...

   Number,Algorithm,System,Embedded system     2011-12-05 12:48:41

  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

  Select top 3 values from each group in a table with SQL

Yesterday, my friend Liu Bing asked me a question about how to select top 3 values for each person in a database table using SQL. I think this question is interesting and it deserves some thoughts. Here I record down how to solve this issue. Assume we have a table which has two columns, one column contains the names of some people and the other column contains some values related to each person. One person can have more than one value. Each value has a numeric type. The question is we want to se...

   SQL,Correlated query,top 3     2013-05-23 03:21:25

  PHP buffer: output_buffering and ob_start

buffer is one piece of memory section, it is usually 4Kb in Linux. It is mainly used between different devices with different speed or different priorities. With buffer, the waiting time between different processes will be reduced. Here is one simple example, when you type something in a text editor, every time when you type a character, the operating system will not write it to the disk directly, instead it will write it to buffer first When the buffer is full, the data in the buffer will be wr...

   PHP buffer,output_buffering,ob_start     2013-06-20 22:54:15

  The 15 Golden Rules of UI design and flow.

Last night a good friend of mine showed me the latest Need for Speed game on the iphone / ipad. Quite an impressive feat of rendering and a relatively good game to boot. However, the front end, wow, a classic case in UI mis-engineering. Loads of stats, pages and pages of bits and pieces to wade through – a classic case of over stimulating the player with lots of decisions they have no business making – stuff that will significantly change their game play experience but being...

   UI design,Game design,Feature     2012-04-05 12:20:18

  Diving Deeper into HTML5 Offline Browsing

Recently, I published an article on one of the new features in HTML 5 called Offline Browsing  in HTML5 with ApplicationCache.The response to that article was good, and I was asked to expand on some further points including:how to decide on what files to cachethe implications of caching those filesdebugging the ApplicationCacheSo, that’s where this article will start: where the last one finished.  If you haven’t, you should probably read the previous article before this o...

   HTML5,Offline browsing,New breakthrough,Feature     2011-12-20 08:46:06

  Create host only network on VirtualBox

Previously we showed how to install Ubuntu in VirtualBox. What if we want to communicate with the host OS from within the Guest OS on VirtualBox? There are a few ways to do this. For example, bridged network, Host only networks. Today we will show you how to enable network communication between host OS and guest OS using host only networks. A host only network will not need to access the physical network interface of the host OS. It will create a network between different virtual machines and th...

   VIRTUALBOX,NETWORK,VIRTUAL MACHINE,HOST-ONLY     2015-12-01 09:29:13

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