Terminal Tools

Markdown to HTML conversion with pandoc

pandoc --metadata title="Markdown to HTML" -s -o markdown_output.html markdown_to_html.md
  • to merge multiple markdown files into a single html, just add more after the first one in a varargs style

  • or pandoc -s -o output.html input*.md in glob style

  • -s
    tells pandoc to create a self-contained file (so it will contain <html></html> tags etc, rather than just generating a fragment)
  • -o
    output.html specifies that output.html will be the output file

FFmpeg

How to extract a frame/frames from a video source in Terminal

Example:

ffmpeg -ss 124 -i input.mp4 -frames:v 1 output.bmp

  • -i url (input)
    input file url

  • -ss position

    • When used as an input option (before -i), seeks in this input file to position. Note that in most formats it is not possible to seek exactly, so ffmpeg will seek to the closest seek point before position. When transcoding and -accurate_seek is enabled (the default), this extra segment between the seek point and position will be decoded and discarded. When doing stream copy or when -noaccurate_seek is used, it will be preserved.
    • When used as an output option (before an output url), decodes but discards input until the timestamps reach position.

  • -frames[:stream_specifier] framecount (output,per-stream)
    Stop writing to the stream after framecount frames.

The Cat's Story

head — Cat’s Head

Read the top of a file. Add -n <number> to specify the number of lines to read or -c <number> for the number of bytes to read.

tail — Cat’s tail

cat — The Complete Cat

cloc

cloc counts blank lines, comment lines, and physical lines of source code in many programming languages.

More info at Github/AlDanial

brew install cloc

direnv

unclutter your .profile

Sources / More on direnv.net

Info

Store your environment variables that you only need in specific folders, in a dedicated .envrc file. That file will be loaded when entering that folder and will be unloaded upon exiting.

This helps to keep your .zshrc, .profile, etc. free of only project-specifically used exported environment variables.

Usage

  1. Navigate to your target folder
  2. Create a .envrc file and move your folder-specific exports and setup here
  3. Security mechanism: Allow the .envrc file. This only has to be done once. 
    direnv allow

Install

Install using Homebrew:

brew install direnv

and add the following line at the end of your .zshrc:

emulate zsh -c "$(direnv hook zsh)"

Compatibility with Powerlevel10k

When you use Powerlevel10k, you may have noticed a warning popping up when you open a new terminal and the opened directory contains a .envrc file.

To avoid that, add the following to your .zshrc file:

emulate zsh -c "$(direnv export zsh)"

## Regular Powerlevel10k setup
if [[ -r "${XDG_CACHE_HOME:-$HOME/.cache}/p10k-instant-prompt-${(%):-%n}.zsh" ]]; then
  source "${XDG_CACHE_HOME:-$HOME/.cache}/p10k-instant-prompt-${(%):-%n}.zsh"
fi

emulate zsh -c "$(direnv hook zsh)"

Source: GitHub user romkatv on issue romkatv/powerlevel10k#702

imagemagick

Install

brew install imagemagick

Use

convert <input-file> <output-file>

jq — Command-line JSON processor

jq can transform JSON in various ways, by selecting, iterating, reducing and otherwise mangling JSON documents.

Easiest:

# file.json:
# {
# 	"version": "1.0.0"
# }
cat file.json | jq ".version"
# prints: "1.0.0"

More complex:

This command will take an array of JSON objects as input and return the sum of their “price” fields

# file.json:
# {
# 	"Lightsaber": {
# 		"price": 1234
# 	},
# 	"Blaster": {
# 		"price": 321
# 	}
# }
cat file.json | jq 'map(.price) | add'
# prints 1555

smartmontools

Install

brew install smartmontools

Use

smartctl -a disk0

speedtest.net

Install

brew install speedtest-cli

Use

speedtest

thefuck

Magnificent app which corrects your previous console command.

Installation

Using Homebrew:

brew install thefuck

Add the following to your .bash_profile, .bashrc or .zshrc:

eval $(thefuck --alias)

and/or

eval $(thefuck --alias fix)

for the SFW version

Github

Find the project at github.com/nvbn/thefuck

Units

  • Huge tool for unit conversion
  • Download from https://www.gnu.org/software/units/
  • How to install/upgrade → see INSTALL file

In short:

cd <directory>
./configure
make
sudo make install

Various Terminal Tools

tr — translate characters

echo "Heeeello" | tr -s "e"
# prints: "Hello"

echo "  He ll o " | tr -d " "
# prints: "Hello"

xargs — construct argument list(s) and execute utility

Use:

echo "He  ll  o" | tr -s " " | xargs echo
# prints: Hello

youtube-dl

Install

brew install youtube-dl

Use

youtube-dl <url>

Allows to download not only from YouTube, but from a huge list of websites, including Vimeo, but also sites like the German Public Broadcast Media Libraries, ARD Mediathek, ZDF Mediathek and many more.