Latex in Jekyll Cheatsheet

Ruby

Rails:
- a web application development framework and
- is based on the Model View Controller (MVC) architecture
- Ruby and Ruby on Rails sound similar because Ruby on Rails was programmed in Ruby and then released to the public in 2005, 10 years after Ruby.
- Ruby on Rails is mostly used for
  - building web applications and
  - server side scripting,
  - but it can also be used to develop interface scripts.
Ruby:
- an open source, object oriented scripting language designed with simplicity as a core focus, and is known for its ability to build online applications quickly.
- Ruby was written in C language
- very popular choice amongst web application development professionals
- can also be used on the back end for data science and memory management purposes

gem

What is a gem?
like “packages” in Python
can be installed with bundle

command	description
`gem list`	list gems
`gem query --local`	list all locally installed gems

bundle

like apt and pip, but for Ruby

command	description
`bundle install`	install all missing gems
`bundle config set --local path 'vendor/bundle'`	to install the gems into `./vendor/bundle/`
`bundle info [gemname]`	to see where a bundled gem is installed

Jekyll

Jekyll is a gem.

Jekyll is written in Ruby.

Ruby 101 explains:
- Gems
  - Gems are code you can include in Ruby projects
  - Ruby gems search
  - Ruby gems list
- Jekyll
  - Jekyll is a gem.
  - Many Jekyll plugins are also gems, including jekyll-feed, jekyll-seo-tag and jekyll-archives.
- Gemfile
  - a list of gems used by your site. Every Jekyll site has a Gemfile in the main folder.
- Bundler
  - Bundler is a gem that installs all gems in your Gemfile.

Check Version

bundle exec jekyll -v

Install and Serve Locally

command	description
`sudo apt-get install ruby-full`
`sudo apt install rubygems-integration`	nicht nötig, wenn `ruby-full` installiert wurde
`sudo gem install bundler`
`sudo gem install jekyll`	Seite funktioniert nicht richtig, wenn dieses Gem nicht installiert wurde (z.B. bei Seitenvergrößerung über `ctrl+` werden die einzelnen Teile der Seite nicht automatisch ausgerichtet)!
`sudo bundle install`	im github-pages repo root folder
`bundle config set --local path 'vendor/bundle'` then `bundle install`	to install the gems into `./vendor/bundle/`
`bundle exec jekyll serve`	warten bis “Server running… press ctrl-c to stop.” message und dann `ctrl` gedrückt halten und auf server address clicken (oder in Browser `http://localhost:4000` aufrufen)

Create a new site

To create a new Jekyll site at ./myblog:

// Create a new Jekyll site
jekyll new myblog

cd myblog

// Build the site and make it available on a local server
bundle exec jekyll serve

Linking to posts

see Jekyll documentation

E.g. this link is a link to the post “Operating Systems Notes”.

Troubleshooting

Incremental Build

problem: suddenly, the incremental build which used to take ca. 2 seconds, now takes ca. 8 seconds
solution:
- stop the currently running bundle exec jekyll serve -I,
- delete the .jekyll-metadata file (what is .jekyll-metadata?)
- rebuild with bundle exec jekyll serve -I

Markdown Syntax

Code Blocks

Liquid Exception: Liquid syntax error (line 194): Variable 'double-{-without-whitespace' was not properly terminated with regexp: /\}\}/ in /home/bra-ket/git/pharath.github.io/_posts/2022-09-22-notes-c.md
             Error: Liquid syntax error (line 194): Variable 'double-{-without-whitespace' was not properly terminated with regexp: /\}\}/
             Error: Run jekyll build --trace for more information.

do not use {{, use { {, i.e. there must be a whitespace between the two curly brackets!

Other

problem: When running ALGOLIA_API_KEY='a8bd11b9f583a3d1f24be7b912c5f430' bundle exec jekyll algolia

jekyll 3.9.4 | Error:  ["//"] is not a symbol nor a string
/var/lib/gems/2.7.0/gems/jekyll-algolia-1.7.1/lib/jekyll/algolia/file_browser.rb:180:in `respond_to?': ["//"] is not a symbol nor a string (TypeError)

solution: Remove all [//]: # ( xyz )-style comments from the frontmatters of all markdown posts.

Latex in Jekyll

conflicts with markdown symbols

# escape with "\" when a symbol causes trouble

# underscore "_"  
\_

brackets

# parentheses (brit.: round brackets):
\(\)

# braces (brit.: curly brackets):
## either
\\{\\}
## or
\{\}

# brackets (brit.: square brackets):
\[\]

bracket sizes

# 1. size can be controlled automatically:
# \left and \right can dynamically adjust the size:
\left( \right)

# 2. size can be controlled explicitly:
\bigl( \Bigl( \biggl( \Biggl(

# for braces:
## either
\bigl\{
## or
\bigl\\{

spaces

\<space>
\,
\quad

formula with cases

# works only inside $$$$
$$
\begin{equation*}
X(\omega) = \begin{cases}
1 &\text{se $\omega\in A$}\\
1250 &\text{se $\omega \in A^c$}
\end{cases}
\end{equation*}
$$

displaystyle vs textstyle

\displaystyle
\textstyle

for example:
- \textstyle Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed dignissim mi sed rutrum mattis. Nulla ligula ante, mattis sit amet aliquam a, tristique eu nisl. $\sum_{n=1}^{\infty}$ (default mode) Duis malesuada libero in lacus viverra, at malesuada ipsum feugiat. Quisque lacinia consectetur dictum. Suspendisse laoreet condimentum lacus, in dictum diam luctus at. Quisque mattis luctus nisl, molestie tempor quam semper a. Etiam tristique cursus libero. Mauris dictum ac nisl ac efficitur.
- \displaystyle Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed dignissim mi sed rutrum mattis. Nulla ligula ante, mattis sit amet aliquam a, tristique eu nisl. $\displaystyle \sum_{n=1}^{\infty}$ (warning: this affects line spacing!) Duis malesuada libero in lacus viverra, at malesuada ipsum feugiat. Quisque lacinia consectetur dictum. Suspendisse laoreet condimentum lacus, in dictum diam luctus at. Quisque mattis luctus nisl, molestie tempor quam semper a. Etiam tristique cursus libero. Mauris dictum ac nisl ac efficitur.

symbols

\circ   # degree, angle

non-standalone symbols (a symbol changing another symbol)

\overline{A}    # instead of "\bar"

absolute value, norm

\vert A\vert
# versus:
\Vert A\Vert

Github Pages

github-pages is a gem.
make sure you have the same github-pages gem version installed locally as github.com (check with bundle list | grep github-pages)

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