Scripting Languages/Meeting Notes 2018-08-20

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

• Scripting Languages/Meeting Notes 2018-08-20

Resources

• TechSoup Canada Catalogue
• GNU Bash
• PowerShell Documentation

Introductions

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

Programming vs. Scripting

• "Programs" are compiled, "Scripts" are interpreted
• BUt mostly there's no differences in syntax
• Brian Kernighan still uses AWK,
  • Touts the advantages of one-liners, which can't be compiled
  • Lecture he gavbe in the UK, "Successful programming language, why are some more successful than others"
    • Keeps coming back to AWK as a successful language

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

• 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 scritping 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 (local level virtual machine) is used to create p[rogramming language
  • take input intermediate language, p-code, generates machine language
  • Needs research. Bob can't figure out what this does
  • LLVM is embedded in CLANG, RUST,
  • way to create code generation for your software

• if all scripting languages were combide, could we reate a universal scripting language?"
  • Probably not -- semantic ambiguity, eg. use of semicolons is different

• Using one language is comforatable, 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 25 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 mo to learn a language for a 2 mo bproject

• "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 ot create aps 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, Santa Fe Institute

• • Other applications like Docker are written in GO, so worth learning

LUA

• LUA: Access to the Linux encryption keyring subsystem
  • Using GUILE (FSF's SCHEME), not so good for encryption
  • "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, unverisity project, released "into the wild"
• Has facility for OOP, but needs your own OOP tools
• Has co-routines, program in loops that are interruptable; daisychain them together
• Functions are first-class entities, so can do functional programming
• Used in games, htere's a modLUA for APache; 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 and an conversion layer for allowing Apache to work with encryption sysstyem
• Definitely a good language for testing
• Bulit 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)

• Is scripting a desirable skillin job applications?
  • Python I sone of the most requested skills
  • But shell scripting is difficult, and
  • For security eg. Wireshark, SNORT, and others need scripting to identify network traffic

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

AWK

• Conrad Grebel prof Dave Huron used AWK to create a catalogue of music for Hewlett-Packard
  • "HumDrum Toolkit" may be 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
  • Standardized CSV files
  • https://sobac.com/sobac/groupwise/code2html/
  • https://sobac.com/bin/awk/

• Much better if data is available though an API, but these scripts were created because there were no APIs

List of scripting languages =

• AWK
• Perl
• Python
• BASH
• PHP
• JavaScript (ECMAScript)
• TROFF
• LUA lua.org, wiki, user groups

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 tools in Linux

• • Muscore has LUA scripting built into it
    • Lilypond has SCHEME or GUILE built in
    • Jon Kulp of Arkansas Uni uses Lilypond (provide links)\

Future TOpics

• November: Tech Wobblies
• December: SOcial Night
• January: GDPR
• February: Network Security
  • Firewall software: pfSense, IPFire, Cisco, Fortinet, Juniper

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