2017 on Simplestory

MySQL Data File Paths on Linux

Fri, 01 Dec 2017 00:00:00 +0000

Server version: 5.7.20-0ubuntu0.16.04.1 (Ubuntu)

After logging into MySQL, you can use the following command to query where the related files are stored:

show variables like '%dir%';

The output is shown below:

Usually these are:

The default location of the database files is: /usr/share/mysql/ Configuration file: /etc/mysql/my.cnf

Database directory: /var/lib/mysql Configuration directory: /etc/share/mysql (mysql.server command and configuration files) MySQL related commands: /usr/bin Startup scripts: /etc/init.d/

One way to start mysql safely: /usr/bin/mysqld_safe-user=root&

Some Linux Commands

Tue, 07 Nov 2017 00:00:00 +0000

Some little-known Linux commands

Detecting Traffic Violations with Opencv

Sun, 05 Nov 2017 00:00:00 +0000

Opencv contains more than 2500 functions, and almost any mature algorithm you can think of can be implemented by calling Opencv’s functions, which is super convenient. This post combines Python and Opencv to detect cars in surveillance video and check whether they commit a violation (crossing the double yellow line).

System environment: Ubuntu16.04LTS+OpenCV3.3.0+Python2.7.12

Background extraction

For surveillance the position is relatively fixed, so the background will not change considerably over a long period of time. We can therefore consider using background subtraction to roughly extract the background.

Installing OpenCV on Linux

Fri, 20 Oct 2017 00:00:00 +0000

Recently, because a project needed computer vision recognition, I started tinkering with OpenCV. Although the installation process was long and winding, the experience of using it together with Python is actually quite good. Here I record the OpenCV installation and compilation process.

System environment: Ubuntu16.04

Software installed: OpenCV3.3.0+Python2.7.12

Updating the system packages:

$ sudo apt update
$ sudo apt upgrade

Installing some developer tools:

$ sudo apt-get install build-essential cmake pkg-config

The pkg-config package is very likely already installed by default, but just in case, add it in as well. The cmake program is used later to compile OpenCV.

Compiling C/C++ under Vscode

Sun, 01 Oct 2017 00:00:00 +0000

Visual Studio Code is a lightweight editor released by Microsoft; by installing various plugins it can be turned into a powerful multi-language, cross-platform compiler. Recently, because of practical needs, I had to debug some C/C++ code, so I started tinkering with Vscode. Below is a record of the problems that troubled me during the process.

The system used in this post is ubuntu16.04LTS

I will not go into the details of installing Vscode on linux, as Baidu has plenty of resources on that.

Python Classes

Sun, 20 Aug 2017 00:00:00 +0000

Life is short, I use Python

Python, Object Oriented

Thu, 10 Aug 2017 00:00:00 +0000

Life is short, I use Python

A Basic Git Tutorial

Tue, 04 Jul 2017 00:00:00 +0000

Some basic Git operations