Scripting Languages/Meeting Notes 2018-08-20

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Scripting Languages

Date
Monday, 20 August 2018 from 7:00pm to 9:00pm iCal
Meetup Event
https://www.meetup.com/NetSquared-Kitchener-Waterloo/events/253044847/
Location
Room 1301 -- Conrad Grebel University College, 140 Westmount Rd. N., Waterloo, Ontario Map
Event Announcement
Scripting Languages/Announcement 2018-08-20

Do you need to do the same thing again and again? Have you automated those repetitive tasks? What software tools do you use? Keyboard macros? Programmable keyboard macros? A scripting language? Which scripting language? What makes a scripting language different from a programming language? Is a scripting language Turing-complete? Can't you just do everything in PowerShell or Bash?

Let's talk about what can be solved with scripting languages, and what can't. Bring your laptop to give a demonstration of your favourite scripting languages, and maybe we can help solve some of your most annoying repetitive problems.


--Bob Jonkman & Marc Paré




Resources


Introductions

  • Testers, programmers, SysAdmins, and some non-scripting users


Meeting Notes

  • Programming vs. Scripting
    • "Programs" are compiled, "Scripts" are interpreted
    • But mostly there's no differences in syntax


  • Use a scripting language to prototype a concept


  • Non-programmers using scripts to do application installation
    • Useful for installing applications without a GUI to get that app installed to the GUI level
    • eg. Mail-In-A-Box, installed with a script


  • Vagrant written in RUBY, but has its own scripting language


  • Lots of variation in scripting language syntax, even within the same language
    • "semicolons forever!"
    • Brackets, or no brackets
    • Is whitespace significant?
    • Indenting
  • many of these are tradeoffs
    • Optimizing for speed, time to program, robustness


  • LLVM (originally Low Level Virtual Machine) is used to create programming language
    • take input intermediate language, p-code, generates machine language
    • Needs research. Bob can't figure out what this does (Wikipedia:LLVM may be helpful}
    • LLVM is embedded in CLANG, RUST, other scripting languages
    • way to create code generation for your software


  • "If all scripting languages were combined, could we create a universal scripting language?"
    • Probably not -- semantic ambiguity, eg. use of semicolons is different in different languages, other syntax doesn't match


  • Using one language is comfortable, so you tend to do everything in that language, appropriate or not
    • What is the lifespan of a language? Depends on the domain -- AWK has been around for 40 years, RUST has not
  • How do you keep up with all the new languages?
    • Need to decide what to give up
    • How much spare time do you have
    • How do you know what new tech to embrace
    • Depends on the lifespan of the project, don't spend 3 months to learn a language for a 2 month project


  • Lambda the ultimate on programming language design
    • There is a formal science to language design


  • Still worth learning C?
    • Yes, it's still efficient, has installed base, still close to the hardware
    • C makes it tolerable to understand what is happening in your computer
    • High level languages have many layers of abstraction
    • Knowing C leads to understanding


  • "Scripting is a gateway drug to programming"


  • How do we learn scripting?
    • Get a raspberry pi
    • JavaScript
    • You need a project to solve!
    • Find something on GitHub
    • Python is considered the preferred entry-level language
    • App Inventor allows people with no programming experience to create apps on Android
    • Scratch is another drag'n'drop learning app
    • Marc taught Logo to a kindergarten class
    • NetLogo used for serious science application, complexity science at Santa Fe Institute
    • Other applications like Docker are written in GO, so worth learning


  • Is scripting a desirable skill in job applications?
    • Python is one of the most requested skills
    • But shell scripting is difficult
    • For security eg. Wireshark, SNORT, &c need scripting to identify network traffic



LUA
  • Kirk wrote in LUA to access the Linux encryption keyring subsystem
    • was using GUILE (FSF's SCHEME), not so good for encryption
    • LUA is "Python for millennials"
  • Written in ANSI C
  • Very embeddable, no linking,
  • Comiles to a Virtual Machine
  • Two flavours, LUA and LUAJIT (Just-In-Time compiler)
  • Seen in XMPP server, used for real-time application
  • Came from Brazil, university project, released "into the wild"
  • Has facility for OOP, but needs your own OOP tools
  • Has co-routines, program in loops that are interruptible; daisychain them together
  • Functions are first-class entities, so can do functional programming
  • There's a modLUA for Apache server; handle data in blocks without touching the Apache system
    • Rather than create a web backend, it lets you create the entire web server
  • "Embeddable extension language"
  • There's a bootloader LUA for use before the OS loads in SysLinux
  • Kirk has used LUA as a conversion layer for allowing Apache to work with encryption sysstyem
  • Definitely a good language for testing
  • Built into Wireshark for decoding packets
  • How popular is LUA? People make stuff available on GitHub
  • LUA is used in games for event handling
  • Many apps have LUA built-in (on the LUA site)
AWK

Wikipedia:AWK

  • Brian Kernighan still uses AWK,


  • "If you want to compile AWK, just re-write it in C"


  • Associative arrays in AWK,
    • Mainstay of Python
    • C only has enumerative arrays, difficult to simulate associative arrays


  • Conrad Grebel prof Dave Huron used AWK to create a catalogue of music for Hewlett-Packard
    • HumDrum Toolkit" is the app name
    • Trying to analyze music, determine patterns among composer
    • Find out if people would be happy if music was two tones up or down
    • Two minutes of this analysis is equal to a human analysis of years
    • Dave Huron one of the first


  • Raymond cleans the data before processing it with AWK
    • Uses BASH to insert parameters begore printing.


  • Bob used AWK to parse log files
    • Poor programming practices - AWK lends itself to quick&dirty hacks, but the scripts grew; good programming practices at the outset would have been beneficial later
    • Much better if data is available though an API, but these scripts were created because there were no APIs
    • Bob implemented a standardized CSV file, but not according to the RFC 4180 specification
    • Human readable: https://sobac.com/sobac/groupwise/code2html/
    • Downloadable: https://sobac.com/bin/awk/


List of scripting languages
Other tools
  • Keystroke macros
    • Record and playback keystrokes
    • Bob wants this to be programmable, depending on input processed
    • AutoIT does this on Windows
    • Not many keystroke macro tools in Linux


Future Topics


Back to: Scripting Languages

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