Flush DNS cache

sudo resolvectl flush-caches

Install dynamic libs *.so

After installing, use ldconf to refresh symbolic links and caches, or apps may not find your newly installed *.so.

rsync vs scp

They are similar tools but you may prefer to use one over another in certain cases:

• scp is …

Common Sense

Tmux is an open-source terminal multiplexer for Unix-like operating systems. It allows multiple terminal sessions to be accessed simultaneously in a single window. It is useful for running more than one command-line program at the same time.

Terms:

• Session: A session can have multiple windows.
• Window: A window …

Source: Regular expression used in Microsoft PowerToy's powerRename

Deep Copy & Copy Constructor

Default Copy Constructor

The compiler also creates a copy constructor if we don’t write our own copy constructor. Unlike the default constructor, the body of the copy constructor created by the compiler is not empty, it copies all data members of the passed object to …

Monoid

monoid=magma+associativity+identity

Magma

A magma is a set M matched with an operation • that sends any two elements a, b ∈ M to another element, a • b ∈ M, i.e. \((M,\cdot)\) is a magma, if

Determinant of …

A

antisymmetric matrix: \(A^T=-A\)

angular frequency: aka, angular velocity, radial frequency and circular frequency. Denoted as \(\omega\)

B

buoyancy: 浮力。

C

curvature: 曲率。

D

directly proportional to: 成正比。

displacement: 位移。注意与distance（路程）区分。

distance: 路程。注意 …

Client <----> CloudFlare <----> VPS

Port Forwarding Using SSH

Sometimes we are faced with the following situation:

graph LR
  A(Computer A)-->|SSH|B(Server A 192.168.1.3)
  B-->|has access via 192.168.1.2:80|C(Server B 192.168.1.2)
  A-->|does not have access|C

Computer A is …

Secure Hashes and Message Digests

Docs: hashlib

SHA1, SHA256 and SHA512 Implementation in JavaScript

Docs: MDN SubtleCrypto.digest()