Sang - Tran Sang Dev Blog (Page 4)

Library path in gcc

Library path in gcc

There are three stages of making your C code run: compilation, linking, and runtime. gcc is mostly responsible for the compilation, while when linking, it uses a linker program (e.g., ld) with some additional flags. 1. In compilation, gcc requires only header (.h) files to ensure that external function

Display binary value as hex

Display binary value as hex

Use od -bc * od: object dump * -b = similar to -t o1, = similar to --format=o1.o1 type mean octal type, 1 bytes per integer. * -c = -t c: printable character or backslash escape Example: print "%s" "${IFS}" | od -bc Result 0000000 040 011 012 000 \t \n \0 0000004

Array variables and their expansion in bash

Array variables and their expansion in bash

Quote escape, word splitting, array usage usually become big struggles for new bash developers. This post will cover around array in bash and related topics. There will be two sections. The first section introduces fundamentals and definitions of arrays in bash. After that, the second section will raise a real-life

Read from stdin in bash

Read from stdin in bash

To read input from stdin to a variable, namely inp. Use read command IFS= read -r inp -r flag is not a mandatory flag but is recommended in most cases. From official read manual by typing help read from command line > -r do not allow backslashes to escape any characters

Collapsing menu bar in mobile with SEO support

Collapsing menu bar in mobile with SEO support

In this post, I will raise some problems when designing a navbar (menu bar) in a web app, and provide solutions to solve each problem. I will use sample code in a react application. The idea is totally the same as is any other framework. When designing a web app

Declare dynamic variables in bash functions

Declare dynamic variables in bash functions

The content of this post will be as the title suggests. My post considers that all variables are not an array. There are 3 ways * Use declare with the global flag -g. Require bash >= 4.2 or zsh foo() { declare -g "my_$1"="my_$2" } foo var val echo $my_

How to change the MAC address in Linux and use time-limited wifi unlimitedly

How to change the MAC address in Linux and use time-limited wifi unlimitedly

In Japan, there are many locations (e.g. airport, convenience store, train stations, ...) where there is free wifi available. Usually, the wifi connection here is limited to a specific time range (e.g. 1 hour). After the connection expires, you have to connect to the wifi again and obtain a

POSA: design patterns with concrete sample code in Javascript/Typescript

POSA: design patterns with concrete sample code in Javascript/Typescript

With or without you realize, your everyday code is using one or many design patterns which are going to be introduced in this post. If you google for Design Patterns, there will be a bunch of blog posts, books that talk about this topic. The recommended book is the canonical

Setup a MongoDB server with docker

Setup a MongoDB server with docker

In this post, I will introduce how to set up a MongoDB database server with docker. The post includes the following sections * Setup a simple MongoDB database server (easy) * Setup a secured MongoDB database server with a password * Secure a currently running MongoDB database server with a password * Periodically backup

You should never use countif function (google spreadsheet)

You should never use countif function (google spreadsheet)

Recently, I was asked to build a shopping order system for my sister. Due to the complexity and ambitiousness of the requirement, I initially chose the google spreadsheet to build a simple system before starting with a web-based system. Then I got to a case that I need to make

Install additional fonts in Ubuntu

Install additional fonts in Ubuntu

Create a directory named .fonts in the home directory if not exist. Then copy downloaded fonts to this directory.

Javascript equality and sameness

Javascript equality and sameness

This is the second post in my Javascript serial [https://transang.me/tag/javascript/]. There are 3 types of comparison operators in Javascript * === (most recommend): strict comparison or identity comparison * == (not recommend): loose comparison * Object.is api [https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is]

Pattern-Oriented Software Architecture - Access control pattern

Pattern-Oriented Software Architecture - Access control pattern

It is often to design a system where the owner does not want to reveal all their data to anyone or be anonymous. For example, bloggers want anonymous users to be able to view their blog posts but they never want any other than editors to be able to edit

Javascript Primitives

Javascript Primitives

Javascript is a very widely used and extremely useful language due to its dynamic. However, there are a lot of concepts in javascript which make developers confused such as data type, class, method inheritance. In this post, I will introduce primitive types in Javascript and related topics. -------------------------------------------------------------------------------- Definition What

Review logicool (logitech) mouse g903h, and mouse pad power-play

Review logicool (logitech) mouse g903h, and mouse pad power-play

Content is written in Vietnamese Trong bài viết này mình sẽ review gear set mouse g903h và mouse pad power-play của logicool (logitech). Nội dung review sẽ không tổng quát hết mà phần lớn sẽ xoay quanh nhu cầu cá nhân. -------------------------------------------------------------------------------- Mouse g903h. Link Amazon [https://www.amazon.co.

To delete or not to delete - practical data archive in database design

To delete or not to delete - practical data archive in database design

One of the common rules when designing a database structure is the structure's ability to keep as much information as possible. In other words, it is not recommended to ever delete any piece of data. Even though they are not visible to the end-user. For example, your database is required

Get current directory absolute path from a bash script

Get current directory absolute path from a bash script

To get the absolute dir of the executing script DIR=$(cd "$(dirname "${BASH_SOURCE[0]}")" >/dev/null 2>&1 && pwd) For sh: DIR=$(cd "$(dirname "$(readlink -f "$0")")" >/dev/null 2>&1 && pwd)

Unlimited emails inbox outbox with just $0.81 per month for all users with sakura domain

Unlimited emails inbox outbox with just $0.81 per month for all users with sakura domain

The following tutorial requires the domain you want to set up bought from sakura. Otherwise, you have to transfer that domain to your sakura account [https://help.sakura.ad.jp/hc/ja/articles/206206431?_ga=2.17384377.1243901636.1565256190-578933206.1565256190] . In addition, you need to buy a sakura mailbox server,

Unlimited emails config with Namecheap domain provider

Unlimited emails config with Namecheap domain provider

Google charges $6 per user per month [https://gsuite.google.com/intl/en/pricing.html], AWS charges by the number of emails sent/received [https://aws.amazon.com/ses/pricing/]. Why not go with FREE (within some limitations)? If you buy a domain from a domain provider which supports email

Get understand the user-agent string of the browser

Get understand the user-agent string of the browser

Let see an example of a user-agent string Mozilla/5.0 (Linux; Android 7.1.1; TONE-m17) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/76.0.3809.89 Mobile Safari/537.36 This is a typical user-agent string whose content is combined of 4 parts * Mozilla/5.0 (Linux; Android

Edit binary file with vim using the xxd command

Edit binary file with vim using the xxd command

To check binary file content xxd To edit a binary file * Open the binary file normally with vim vim * Convert them to xxd human-readable format :%!xxd * Edit the hex part in the left * Convert xxd human-readable format back to binary :%!xxd -r * Save modified content :w Here are some useful

How to convert file encoding

How to convert file encoding

In this post, I will introduce 2 ways to convert file encoding Method 1: use Linux command iconv iconv -f sjis -t utf-8 -o The file is read in sjis encoding and re-written to in utf-8 encoding. Here is the explanation of the flag: * -f: from * -t: to * -o: output

Encrypt/Decrypt files/directories with openssl

Encrypt/Decrypt files/directories with openssl

Assume that you have a single file to encrypt/decrypt. * To encrypt openssl enc -pbkdf2 \ -in "${file_name}" \ -out "${file_name}.enc" \ -md sha512 -salt \ -pass "pass:${my_password}" ${file_name} is the name of the file you want to encrypt. Encrypted data will be stored in ${file_name}.enc.

Cấu hình SSL (https) tự động siêu đơn giản khổng lồ với chỉ 1 dòng lệnh

Cấu hình SSL (https) tự động siêu đơn giản khổng lồ với chỉ 1 dòng lệnh

English version here [https://transang.me/setup-nginx-server-with-ssl/] Gần đây do cá nhân cần quản lý nhiều tên miền trên nhiều máy chủ nên dần cảm thấy việc cài đặt từng máy chủ một khá là mất công. Nhất là khi khởi động lại, chuyển nhà, nâng cấp, hoặc cập nhật

Setup an Nginx server with SSL in one command line

Setup an Nginx server with SSL in one command line

Recently, due to the need for multiple servers/domain management personally, I feel waste of time to config the server one by one. Especially, when server restart, migration, upgrade, SSL certificate update. Thus, I have made a Github project [https://github.com/tranvansang/ssl] to accomplish this task automatically. This