Shell Scripting Fundamentals

July 25, 2022 · 23 min read

Shell is the language we use to communicate with the operating system through the command line.

Shell scripts can run directly on the command line, or a set of logic can be organized into a file for reuse. The command line can be thought of as a “shell script executing line by line.”

There are many common kinds of shell scripts in Linux, including:

• Bourne Shell (/usr/bin/sh or /bin/sh)
• Bourne Again Shell (/bin/bash)
• C Shell (/usr/bin/csh)
• K Shell (/usr/bin/ksh)
• zsh
• …

Linux systems generally use bash by default.

The file should begin with #! /bin/bash to specify bash as the script interpreter.

Introduction to CUDA

July 8, 2022 · 1 min read

介绍 CUDA 的基本概念、支持的编程语言、发展历程及 GPU 加速计算的应用。

MySQL Cheatsheet

March 15, 2022 · 84 min read

整理 MySQL 常用语法、函数、约束、多表查询和事务，并介绍存储引擎、索引、执行计划与 SQL 性能优化。 文中的密码仅作示例，实际使用时请独立生成。

Image Classification and Foundational Vision Models

March 7, 2022 · 3 min read

Process #

1. Collect data

2. Define the model

   Usually a function containing parameter variables: \(y=F_{\Theta}(X)\)

   Example: \(y=\sigma\left(\Theta^{T} X\right)\)

3. Train Find the optimal parameters \(\Theta^{*}\) so that the model \(y=F_{\Theta^{*}}(X)\) achieves the highest accuracy on the training set

4. Predict For a new image \(\hat{X}\) , use the trained model to predict its class, namely \(\hat{y}=F_{\Theta^{*}}(\hat{X})\)

SSH Remote Access and File Transfer

February 12, 2022 · 4 min read

Log In to the Server #

ssh user@hostname

• user: username
• hostname: IP address or domain name

The first time you log in, you will see this prompt:

The authenticity of host '123.57.47.211 (123.57.47.211)' can't be established.
ECDSA key fingerprint is SHA256:iy237yysfCe013/l+
Are you sure you want to continue connecting (yes/no/[fingerprint])?

Enter yes and press Enter. This records the server’s information in ~/.ssh/known_hosts.

Then enter the password to log in to the remote server. The default login port is 22. To log in through a specific port:

ssh user@hostname -p 22

Introduction to Web APIs

July 10, 2021 · 3 min read

Strictly speaking, most of what we learned in the JavaScript section belongs to ECMAScript. ECMAScript, or ES, defines language standards such as the syntax rules for variables, data types, expressions, statements, and functions. Browsers implement most of the ECMAScript specification and extend it with practical features. These extensions are called Web APIs.

JavaScript Data Types

July 9, 2021 · 3 min read

JavaScript is a weakly typed, or dynamic, language. You do not need to declare a variable’s type in advance; its type is determined automatically while the program runs.

var age = 10; // Number
var areYouOk = 'yes'; // String

JavaScript has dynamic types, meaning the same variable can be used for different types (its type can change).

var x = 6; // x is a number
var x = "Bill"; // x is a string

JavaScript Objects

July 9, 2021 · 5 min read

Objects are a JavaScript data type. We have already learned about numbers, strings, booleans, and undefined. An object can be understood as a collection of data. It consists of properties and methods.

JavaScript Functions

July 9, 2021 · 3 min read

Declaration (Definition) #

Declaring (defining) a complete function involves five parts: the keyword, function name, formal parameters, function body, and return value.

JavaScript Arrays

July 9, 2021 · 2 min read

Arrays: An array is a data type that stores data in order.