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  Python internals: how callables work

[The Python version described in this article is 3.x, more specifically - the 3.3 alpha release of CPython.] The concept of a callable is fundamental in Python. When thinking about what can be "called", the immediately obvious answer is functions. Whether it’s user defined functions (written by you), or builtin functions (most probably implemented in C inside the CPython interpreter), functions were meant to be called, right? Well, there are also methods, but they’re not very ...

   Python,Callable work,Rationale     2012-03-24 05:20:27

  A HTTPS client and HTTPS server demo in Java

In this post, I will create a HTTPS server and HTTPS client demo which can establish HTTPS communication between a server and a client using Java. This should be very useful when we want to test our understanding about SSL communication. We will use both a detailed SSL client and a simple HttpsURLConnection as the HTTPS client. Before creating the actual HTTPS server and HTTPS client, we first need to generate the keystore and truststore to be used by the server and client. To generate the keyst...

   SSL,HTTPS,JAVA,DEMO     2015-10-23 09:04:36

  How to find which process a file is being written by in Linux?

Some people ask a file is being written by one process and they want to check this process, but they cannot find the process even with sof. This question is very common and there are many solutions, here we introduce a straightforward method. In Linux, each file will be stored on one device and of course there will be a relative inode, then we can use vfs.write to know who is writing the inode on one specified device continuously. Luckily there is inodewatch.stp in the installation package of s...

   Linux,process,file write     2013-03-16 21:44:35

  Beginners guide to Linux directory structure

Have you ever looked in your / directory, you’ll see a lot of directories. Here we are presenting beginners guide to linux directory structure explaining what they mean and what are the contents of these directories.Screenshot of contents of root directory: /This is called root partition. All files and directories start with root partition. Write privileges under this directory are avaible with root user only. Not to confuse it with root user’s home directory, know the ...

   Linux,File system structure,Beginner's guide     2012-04-20 12:19:32

  10 tools to make your shell script more powerful

Many people mistakenly think that shell scripts can only be run in command line. In fact shell can also call some GUI components such as menus,alert dialogs, progress bar etc. You can control the final output, cursor position and various output effects. Here we introduce some tools which can help you create powerful, interactive and user friendly Unix/Linux shell scripts. 1. notify-send This command can let you inform the process to send a desktop notification to users. This can be used to send ...

   shell,GUI,zenity     2013-04-05 08:50:41

  A String is not an Error

I decided to write a little article to discourage an unfortunately common pattern in Node.JS modules (and browser JavaScript, to a lesser extent) that can boil down to these two examples: // A:function myFunction () {  if (somethingWrong) {    throw 'This is my error'  }  return allGood;} and // B: async Node.JS-style callback with signature `fn(err, …)`function myFunction (callback) {  doSomethingAsync(function () {    // …    if (...

   JavaScript,Node.js,String,Error object     2011-12-23 08:00:32

  Concise bash programming skills

The following are some concise bash programming skills which we may need in our daily programming work. 1. Check status of command execution The usual way: echo abcdee | grep -q abcd   if [ $? -eq 0 ]; then echo "Found" else echo "Not found" fi Concise way: if echo abcdee | grep -q abc; then echo "Found" else echo "Not found" fi Of course you can remove if...else with following code [Sun Nov 04 05:58 AM] [kodango@devops] ~/workspace $ echo abcdee | grep -q ...

   bash, skill,tip     2012-11-06 10:38:42

  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

  Different types of keystore in Java -- JKS

JKS is Java Keystore, a proprietary keystore type designed for Java. It can be used to store private keys and certificates used for SSL communication, it cannot store secret keys however. The keytool shipped with JDKs cannot extract private keys stored on JKS. This type of keystore usually has an extension of jks. Next we will show how to operate the JKS keystore with pure Java code. Create JKS keystore The simplest method to create a JKS keystore to create an empty keystore. We can first get an...

   DEMO,EXAMPLE,KEYSTORE,JKS     2014-09-05 20:21:51

  The ugliest C feature:

<tgmath.h> is a header provided by the standard C library, introduced in C99 to allow easier porting of Fortran numerical software to C. Fortran, unlike C, provides “intrinsic functions”, which are a part of the language and behave more like operators. While ordinary (“external”) functions behave similarly to C functions with respect to types (the types of arguments and parameters must match and the restult type is fixed), intrinsic functions accept arguments of...

   C,,Fortran,Intrinsic functions,C99,Ugly     2011-12-26 08:33:27

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