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  Some cases where MySQL cannot be started

After installing MySQL, when we try to start MySQL, sometimes we may not be able to start it. The reasons can be different. We share some general cases where MySQL cannot be started. Case 1: Directory or file permission issue If the permission is set wrongly in MySQL's $datadir and its sub directories or files, MySQL will not be able to read and write files normally. Error message: mysqld_safe Starting mysqld daemon with databases from /usr/local/mysql/data /usr/local/mysql/bin/mysqld_safe: lin...

   MySQL,Error,Log     2013-08-15 03:32:36

  How to handle ES6 modules in NodeJS

In modern JavaScript, there are two types of modules: ES6 module and CommonJS module used by NodeJS. These two types of module are not compatible. Many people would wonder how to load ES6 modules in their NodeJS project. This post will show how this can be done. Difference The syntax of the module being loaded is different. CommonJS modules are loaded with require() and exported with module.exports. ES6 modules are loaded and exported using import and export respectively. Merchanismwise require(...

   NODEJS,COMMONJS,ES6     2020-08-28 22:01:33

  System programming is still there

System programming is the practice of writing system software. System software lives at a low level, interfacing directly with the kernel and core system libraries. Your shell and your text editor, your compiler and your debugger, your core utilities and system daemons are all system software. But so are the network server, the web server, and the database. These components are entirely system software, primarily if not exclusively interfacing with the kernel and the C library. But nowadays more...

   System programming     2014-02-27 05:46:48

  Common usage of ls command in Linux

In Linux, ls might be one of the most frequently used commands. It is used to list files in a specific directory. In most cases, we may just use ls -l to list the files under a directory. But have you explored other usages of this command. In this post, we will summarise some other common usages of ls command Assuming we have below directory structure in our system, let's see them using tree command. List details of the files If we want to list the details of the files in /home/alvin/test_...

   LINUX,SHELL,LS     2018-12-16 03:00:42

  Remove browse button from input type=file

In Web 2.0 era, many websites will ask the user to upload their avatar when creating their profile. In HTML, the input control we should use is input="file". This is a file control provided by the browser vendor and it should be ran in a sandbox for security consideration. Browsers don't provide ways to choose file from local and upload to the remote server without the input="file" control.  There is one annoying part about the input="file", which is a default button named "Choose File" or...

   file,html,browse,remove browse button     2015-07-12 05:17:51

  New Features to Look Out for in Xcode 9

When we say Xcode, we mean a designing toolset which is completely packed with features. Using this Xcode, developers can create applications for platforms such as the Apple TV, the iPad, Apple Watch, and the iPhones and even for the Macintosh. The development system for Xcode has a mixture of features. These are called the instrument analysis tool, simulators, and the ever important OS frameworks which are present in the package in a variety of form of tvOS SDKs, iOS SDKs, watchOS SDKs, and the...

   XCODE,IPHONE,XCODE9     2017-09-26 06:31:30

  Supervisord, God and Monit, which one to choose?

With the popularity of Docker, more and more service have been moved into docker containers and they are easy to build up and maintain for each atomic service(though it's a bit complex to maintain multiple docker containers which contain different service to form a complete solution). Ideally, each docker container should only contain one service which has only one running process. However, in reality there would be cases multiple processes would run in one single docker container and there is a...

   DEVOPS,MONIT,SUPERVISORD,GOD,DOCKER     2017-11-25 12:28:11

  Understand diff in Unix

diff is an important tool program in Unix. It is used to compare differences of two files, it is the foundation for code version control. If you type : $ diff <file_before_change> <file_after_change> diff will tell you what's the difference between these two files. The result may not be so easy to understand, so now I will show you how to understand diff. 1. 3 formats of diff diff has 3 formats due to historic reasons. normal diff context diff unified diff 2. Demo files For easy d...

   diff,Unix,version control,git     2012-09-03 10:49:36

  Unknown system variable 'query_cache_size' in DbVisualizer while accessing MySQL

DbVisualizer is a very popular GUI application to view the data stored on a database. It supports various databases such as Oracle, MySQL etc. It relies on different database drivers to connect to the database server and access the data stored there.  In this post, we will try to solve one problem when accessing the latest MySQL database(8.0+) through DbVisualizer. MySQL database starting from 8.0 has lots of changes which may not be compatible with old version of software or libraries whic...

   MYSQL,MYSQL 8,DBVISUALIZER,QUERY_CACHE_SIZE     2018-06-30 03:48:17

  Output a file with HTTP range header in PHP

When downloading a large file, we may encounter some network issues which causes download termination and only part of the file is downloaded. When the network connection resumes next time, we may need to redownload the file again from the beginning. In order to save bandwidth, http provides a Range parameter in its header which can control the file transfer flow. With the range parameter in the header, we can resume the download from where we stop. Here is a piece of PHP code snippet which uses...

   PHP, range,http, file transfer     2013-01-09 05:55:05

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