Minutes 2026-10-29

BASH scripting by Freya!

Scripting?

   Executables are not binary
   Files start with #! (Shebang)
       Defines what binary to run the file in
       Usually /bin/bash
       Can do it with other programming langues or anything!
   Good for automation/customization

What languages?

   Any
   Can even do auto-compiled C with GCC
   Usually POSIX shell like bash
       env/bin/bash is more 'proper'
   Python
       Some scripts on your system
       Pacman
   Other shells
       fish, csh, zsh
   Shell (server) uses ZSH
   Other shells come with their own languages since that's just what they are
   All high-level
       All terminal commands are shell commands
       Pipes (part of bash language)
       Bash is part of POSIX standard so it's common on Linux/UNIX
   Bash language
       It's old
           Bounre shell
           Dates back to 60s

Use cases

   Run scripts on keybind
       You can bind any executable to a keybind
       Shortcuts (open apps) as well
   See the weather
   Interactive menus
       dmenu
       Take in a list of things and sort through them
           Useful for menus
   Repetitive tasks
   Examples:
       Transferring pictures off a camera
   Freya found a Youtube channel with a lot of cool shell scripts
       Videos edited with scripts
           Automated FFmpeg scripts
   Stringing together data
       Screenshots
           Can use slurp/grim on Wayland
       Usually scripted
           Can make it dynamic
   Process data

Basics of bash

   No built in functions
       Just call commandline applications
   Built on commands like cs, ls
   Familiar if you use CLI a lot
   Bash environment is entirely dependent on what you have installed
       JSON parsing (bad) and dependent on system packages
   Lots of cool programs to do nice things
   Environment variables
       Just a bash variable
       East to access in shell environments
       They can be complicated on other languages
   Awful syntax but decently powerful
   Good for stringing commands together with pipes
   Variables
       Assign a string to a name
       Easy to access with $
   Echo
       Print statements
   Read lines from standard input
       Grab user data
   If statements must end in fi
       Some bash statements are ended with themselves backwards
       Really weird getting arguments
           Square brackets with required spaces
           Brackets are technically a command...
   Typical programming languages things (Loops, brackets, else-if)
   Bash is a mess....
       Is this how professors feel teaching Java 8 to students?
       Or C89?
   Exit codes are like return statements to exit or give errors

Built-in things

   $n gets number 0 to 9
   $? gets error codes
       See if program failed unless it's being weird
   $@ gets arguments as arrays
   $! gets PID of background commnand
       Lets you run things asynchronously

Environment values

   Home directory
   Current username
   PATH variable
   XDG variables
       .config
       cache home
       local home
   Don't hardcode paths, use variables instead
       Better for portability

Things to remember

   Commands make life easy
   Learn to use awk, sed, and jq
       Text replacement
       JSON parsing
   Curl for internet stuff
       Or wget
   There's functions
       Make things easy for yourself
       But nobody uses them except for fork bombs

Demo time!

   Window manager mishaps...
   Example scripts
   National weather service provides prerendered radar GIFs
       Just a URL
       Always updated
       Can grab them with a script
           Downloads the gif to /tmp and plays it
       Make widgets?
       Uses just curl and mpv
   QR generator script
       Save text
       qrencode then print as image
   Scan QR from screen or camera
   All very simple, just stringing shell commands together
   Aurora script
       Shows it on a map in a window
       Free API from NOAA
       Graph of probability
   Script to add todo list item
       Doesn't work...
   Brightness control
       Drivers for brightnessctl may be broken
       Complaining about chromeOS?
       Converts value to percentage
       Hardcoded path.....
   Waybar extension
       Outputs todo status to the bar
       Just a loop to show items

Cronjobs

   Do custom things on schedules
       Weather alerts

Scripting Magnum Opus

   Grabs days of weathers
   Pulled from weather services
   Only took 2 hours
   Very easy
   It's free!
       Don't pay for weather APIs
       National weather service is free and good
       Raw model data is also free
           Even the notes they're taking
   Forecast function takes in URLs and outputs JSON
   Freya also wrote scripts for brightness and volume
   Wants to bind it to a shortcut

Inspiration

   Bread on Penguins
       Videos showing scripts
       Automated with ffmpeg
       Cool things

One more thing

   LUG lan party 3 on Sunday

End