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  An experience of fixing a memory-corruption bug

During the last 4 months, I was disturbed by a memory-corruption bug, and this bug will cause program crash. Until last Monday, I found the root cause and fixed it. This debug process is a difficult but memorable experience, so I will share it in this article.   My program works as a SMS Hub. When it receives a SMS, it will allocate a structure in heap memory like this: typedef struct { ...... int *a[8]; ...... } info; After processing the SMS, the program will free the m...

   c, debug, unix, solaris, multi-thread     2014-05-04 03:52:43

  Create namespace in JavaScript

A namespace (sometimes also called a name scope) is an abstract container or environment created to hold a logical grouping of unique identifiers or symbols (i.e., names). An identifier defined in a namespace is associated only with that namespace. The same identifier can be independently defined in multiple namespaces. That is, the meaning associated with an identifier defined in one namespace may or may not have the same meaning as the same identifier defined in another namespace. Languag...

   JavaScript,namespace,example     2012-05-10 04:57:17

  Using htpasswd to protect your website in Nginx

We need to build a password protected website frequently such as an internal website within the team, demo website. Here what we are talking about is password protection in Nginx server level instead of application level registration and login. We are going to use Nginx server configuration and htpasswd file to achieve password authentication. The final result looks like below(Different browsers may have different interfaces): If the authentication fails, it will report a HTTP error: 401 Author...

   Nginx,Password protected,htpasswd     2013-06-07 21:35:27

  Unix directory hierarchy history

As a beginner user of Unix or Linux, people would frequently get confused about the use of different directories of the system.  For example, there is a /bin directory under root(/), it is used to store binary files. However, there are /usr/bin and /usr/local/bin under /usr which are used for storing binary files as well. Some systems even have /opt/bin. What are the differences among them? Though there are articles explaining different directories in *nix such as Filesystem Hierarchy Stan...

   UNIX,LINUX,FILESSYTEM,DIRECTORY HIERARCHY,HISTORY     2016-10-21 23:47:17

  37 powerful Linux shell commands

To work on Linux platform, you cannot avoid using shell commands to complete some tasks. These tasks can be as simple as list files in some directories or find some text in some file, or can be as complex as monitoring processes. In this post, we will share 37 powerful Linux shell commands.   Task Commands 1 Delete file with 0 byte(empty file) find . -type f -size 0 -exec rm -rf {} \;find . type f -size 0 -delete 2 Check process memory consumption ps -e -o "%C : %p : %z : %a"|sort -k...

   Linux command,List     2013-09-16 07:47:16

  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

  Different types of keystore in Java -- BKS

BKS is a keystore format provided by the popular third party Java cryptographic library provider -- BouncyCastle. It is a keystore similar to the JKS provided by Oracle JDK.  Before starting to use BKS, the BouncyCastle provider has to be downloaded and installed. To download the provider, please go to BouncyCastle download page. The provider can be installed by adding an entry in the java.security file. security.provider.N=org.bouncycastle.jce.provider.BouncyCastleProvider N means the pr...

   JAVA,KEYSTORE,BOUNCYCASTLE,BKS     2016-07-03 03:00:18

  Install LAMP in two easy steps

You might have seen my earlier post related to installing PHP, Apache and MySQL on UBUNTU 11.10. That process contains number of steps and some lengthy commands which we can not remember easily. After good comments from Gaurav and Coward I have managed to get that lengthy process in just 2 steps. So I thought its great to share with all readers to they can get benefit as...

   LAMP,PHP,Steps,Tutorial     2012-04-30 09:15:28

  Remote execute command in Java example

Frequently there is a need to logon to a remote system and run some commands or programs to get the output, many software can serve this purpose such as putty and gitshell.These software usually provide secure access to the remote system. But have you ever wondered what to do if you need to run commands on many different systems at the same time and get all these results back at a single place? Especially in big data era, many tasks may run on different distributed systems and you want o have a ...

   JSch, Example, Distributed system, SSH2     2014-12-12 03:20:19

  A serious security vulnerability found in MySQL/MariaDB

Recently a serious security vulnerability was found in MySQL/MariaDB. It relates to the access to the database. The issue is described below.When a user connects to MariaDB/MySQL, a token (SHA over a password and a random scramble string) is calculated and compared with the expected value. Because of incorrect casting, it might've happened that the token and the expected value were considered equal, even if the memcmp() returned a non-zero value. In this case MySQL/MariaDB would think that the p...

   MySQL,MariaDB,bug,fix,password,memcmp()     2012-06-11 10:28:09

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