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Python: load a script in Python shell

This is usually for some quick testing.

1. python -i myscript.py

   Then you can reference functions and variables in the script directly.

2. While you are already in a Python shell:

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pip was broken after I installed pip3.8 and removed some other python links.

To fix pip:

python2 -m pip install --user --upgrade pip

python3 -m pip install --user --upgrade pip

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Set environment variables for proxies.

Windows:
set http_proxy=http://xxx.xxx.xxx.xxx:80
set https_proxy=http://xxx.xxx.xxx.xxx:80

Bash:
http_proxy=http://xxx.xxx.xxx.xxx:80
https_proxy=http://xxx.xxx.xxx.xxx:80

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Common Useful MySQL / MariaDB Commands

User Creation, Manipulation, Deletion

• Show all users in the mysql database:

  MariaDB [(none)]> select * from mysql.user;

• Delete a null user:

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Install WordPress v5.3.2 and self-host it over https using Nginx.

Prerequisites

1. MariaDB 10.4.13 (Reference How To Install MariaDB 10.4 on Ubuntu 18.04 / Ubuntu 16.04)

2. php 7.4.3 (Reference How To Install PHP 7.4 on Ubuntu 20.04/18.04/16.04)

   php installs Apache2 too. Disable it and remove it if you want to use Nginx.

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Perl:
print "$^V\n"; # 5.26.1
print "$]\n"; # 5.026001

Python:
import sys
print(sys.version) # 3.7.0 (v3.7.0:1bf9cc5093, Jun 27 2018, 04:59:51) [MSC v.1914 64 bit (AMD64)]
print(sys.version_info) # sys.version_info(major=3, minor=7, micro=0, releaselevel='final', serial=0)
import platform
print(platform.python_version()) # 3.7.0

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const fs = require('fs');

function packFile(filename, outfilename, noOfBytesToPrefix = 100) {
    const filenameEncoded = new Buffer.from(filename, 'utf8');
    const filenameLength = filenameEncoded.length;
    if (filenameLength > noOfBytesToPrefix) {
        throw new Error("file name after utf-8 encoding is too long");
    }
    
    let prefixBuffer = new Buffer.allocUnsafe(noOfBytesToPrefix).fill(0);

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const crypto = require('crypto');
const util = require('util');

const randomBytes = util.promisify(crypto.randomBytes);

async function hashPassword(password) {
  // Hash a password for storing.
  try {
    const buf = await randomBytes(64);
    const salt = crypto.createHash('sha256').update(buf.toString('hex')).digest('hex');

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import hashlib, binascii, os

def hash_password(password):
    """Hash a password for storing."""
    salt = hashlib.sha256(os.urandom(60)).hexdigest().encode('ascii')
    pwdhash = hashlib.pbkdf2_hmac('sha512', password.encode('utf-8'), 
                                salt, 100000)
    pwdhash = binascii.hexlify(pwdhash)
    return (salt + pwdhash).decode('ascii')

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def pack_file(file_name, outfile_name, no_of_bytes_to_prefix=100):
    file_name_encoded = bytes(file_name, encoding='utf-8')
    file_name_length = len(file_name_encoded)
    if file_name_length > no_of_bytes_to_prefix:
        raise Exception('file name after utf-8 encoding is too long')
    prefixed_bytes = bytearray(no_of_bytes_to_prefix)
    prefixed_bytes[0:file_name_length] = file_name_encoded
    
    chunk_buffer = 4096
    with open(file_name, 'rb') as infile, open(outfile_name, 'wb') as outfile: