This guide explains how to set up a Raspberry Pi without needing a monitor.

• Requires a Raspberry Pi device that can connect an Ethernet cable for a wired connection.
• A computer is needed to operate the Raspberry Pi.

Install Raspberry Pi Imager, select the OS. Choose the micro SD card to write to, and click WRITE.

Configuration

Enable SSH​

Enabling SSH allows you to operate the Raspberry Pi remotely.

Reinsert the micro SD card and create a text file named ssh directly in the root directory. No extension is needed.

Enable VNC​

Open config.txt and uncomment and save the following lines:

framebuffer_width=1280
framebuffer_height=720

Boot Up​

Insert the micro SD card into the Raspberry Pi, connect the power, and boot it up.

Connect via SSH​

Connect using hostname raspberrypi, username pi, and password raspberry.

Update Packages​

sudo apt update
sudo apt upgrade -y

Enable VNC​

sudo raspi-config

Select 3 Interface Options, then P3 VNC, and select YES. Close with Finish.

Connect via VNC​

Use the same username and password as for SSH.

Enable Wi-Fi​

Enabling Wi-Fi via VNC eliminates the need for a wired connection, allowing you to operate the Raspberry Pi with only power.

When executing CGI in the browser, an error occurs stating: /usr/bin/env: 'ruby': No such file or directory

#!/usr/bin/env ruby

# ...

Cause

The $PATH is not set.

#!/usr/bin/env bash

echo -ne "Content-type: text/html\n\n"
echo $PATH

Running this will display:

/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

This shows that the directory containing Ruby is not present.

Solution

Set the Ruby path using :CGIPathEnv.

srv = WEBrick::HTTPServer.new({
   :DocumentRoot => "./site/",
   :Port => 8080,
   :CGIPathEnv => ENV["PATH"]
})

Creating a Template​

bundle gem <GEM Name> -t
cd <GEM Name>

Editing the Gemspec​

0. Open <GEM Name>.gemspec.
1. Edit spec.summary, spec.description, spec.homepage,
2. Write the homepage URL to spec.metadata["allowed_push_host"]
3. Write the Gem's page to spec.homepage
4. Write the repository URL to spec.metadata["source_code_uri"]
5. Write the URL of changelog.md to spec.metadata["changelog_uri"]

Set at least this much.

Push to GitHub and Install​

git init
git add .
git commit -m First Commit
git remote add origin [email protected]:<username>/<GEM Name>.git
git push -u origin master

Install​

gem install specific_instal
gem specific_install -l "git://github.com/<username>/<GEM Name>.git"

Gemfile​

gem "<GEM Name>", github: "<username>/<GEM Name>.git", branch: :main

Introducing the tiv command for displaying images in the terminal.

It's convenient when you don't want to open a file explorer.

git clone https://github.com/stefanhaustein/TerminalImageViewer.git
cd TerminalImageViewer/src/main/cpp
make -j
sudo make install

An attempt to apply a bilateral filter using ImageMagick. For installation instructions for ImageMagick, see install-magick.html

magick convert Parrots.jpg -bilateral-blur 10x10 output.png

Results

• Input image

  

• Output image

  

0. Let C be the remainder when A is divided by B.

1. Let D be the remainder when B is divided by C.

2. Let E be the remainder when C is divided by D.

   ...

3. Let Y be the remainder when X is divided by 0.

   Then Y is the greatest common divisor.

Bash Script

#!/usr/bin/env bash

function gcd(){
   test $2 -eq 0 && echo $1 || gcd $2 $(( $1 % $2 ))
}

gcd 1071 1029
# 21

wget https://download.imagemagick.org/ImageMagick/download/ImageMagick-7.0.11-14.tar.xz

Extract

tar xf ImageMagick-7.0.11-14.tar.xz

Make

sudo apt update
cd ImageMagick-7.0.11-14.tar.xz
./configure
make -j
sudo make install
sudo ldconfig /usr/local/lib

As an example, let's use a 1[Hz] sine wave as the signal. Add noise generated from random numbers following a normal distribution with a mean of 0 and a standard deviation of 0.5 to the signal.

import numpy as np
import matplotlib.pyplot as plt
from scipy.ndimage import gaussian_filter1d

t = np.arange(1000) / 100
s = np.sin(2*np.pi*t)
noise = np.random.normal(0, 0.5, size=len(t))
x = s + noise

plt.plot(t, x, label="+noise")
plt.plot(t, s, label="signal")
plt.legend(loc=1)
plt.show()

Apply a Gaussian filter with a standard deviation of 5. The larger the standard deviation, the smoother the result, but the more it deviates from the original signal.

y = gaussian_filter1d(x, 5)
plt.plot(t, y, label="filtered")
plt.plot(t, s, label="signal")
plt.legend(loc=1)
plt.show()

Updating pip​

python -m pip install --upgrade pip

Installing with pip​

pip install jupyterlab

Launching​

jupyter lab --no-browser

0. Clone Pyenv Clone the Pyenv repository. The recommended directory is ~/ .pyenv.

git clone https://github.com/pyenv/pyenv ~/.pyenv

0. Compile Bash extensions for speed
   You can compile Bash extensions for speed.
   It will still work correctly if the compilation fails.

   ```sh
cd ~/.pyenv && src/configure && make -C src

0. Configuration (bash) Path and other settings.

echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.profile echo 'export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.profile echo 'eval "$(pyenv init --path)"' >> ~/.profile export PYENV_ROOT="$HOME/.pyenv" export PATH="$PYENV_ROOT/bin:$PATH" eval "$(pyenv init --path)" echo -e 'if shopt -q login_shell; then'
'\n export PYENV_ROOT="$HOME/.pyenv"'
'\n export PATH="$PYENV_ROOT/bin:$PATH"'
'\n eval "$(pyenv init --path)"'
'\nfi' >> /.bashrc echo -e 'if [ -z "$BASH_VERSION" ]; then'
'\n export PYENV_ROOT="$HOME/.pyenv"'
'\n export PATH="$PYENV_ROOT/bin:$PATH"'
'\n eval "$(pyenv init --path)"'
'\nfi' >>/.profile

# Installing Python Environments

## Installing Dependencies
```sh
sudo apt-get update; sudo apt-get install make build-essential libssl-dev zlib1g-dev \
libbz2-dev libreadline-dev libsqlite3-dev wget curl llvm \
libncurses-dev xz-utils tk-dev libxml2-dev libxmlsec1-dev libffi-dev liblemgma-dev -y

Checking Installable Environments​

pyenv install -l

Installing​

It takes a long time to compile, so please wait.

CONFIGURE_OPTS= "--enable-shared" pyenv install 3.9.5

Verifying Version​

pyenv versions

Switching Version​

pyenv global 3.9.5