Scripting Languages¶

Course Information¶

based off notes from Dan Hood

Contact Information¶

Bryan Wilkinson¶

bryan.wilkinson@umbc.edu
ITE 373
Office Hours: Mondays 10:30 AM - 11:30 AM and Thursdays 3:00 PM - 4:30 PM
or by appointment
Website: https://www.csee.umbc.edu/courses/undergraduate/433/spring18/

Tips for This Course¶

• Be comfortable looking things up with resources I have provided, as well as coming to me for help
• Start Projects Early
  • Quizzes are meant to be a motivation
• Don't try to write down everything on a slide, use the slides provided and take notes on top of that

Example Quiz Question¶

• Which of the following character classes matches all types of white space
  • \w
  • \s
  • \S
  • \t

Example Quiz Question¶

What is the output of the following code and why?

case 9 in
    *9)
        echo "This ends in a nine"
        ;;
    9)
        echo "This is a nine"
        ;;
    *)
        echo "Nothing Matched"
        ;;
esac

Example Quiz Question¶

• Briefly describe what benefit AJAX provides. What type of websites and interactions on those websites does it enable that would not be possible without it? (2-3 sentences)

Scripting Languages¶

• Usually interpreted
  • Rapid development
  • Portability - cross platform
  • Slower - less than in the past
• Don't need a main
  • But can have one

Scripting Languages¶

• Good to integerate existing programs with
• Flexible
  • Easy to extend
  • Lots of libraries available for each language
  • Usually a very easy way of installing them

REPL¶

• One of the most common characteristics of scripting languages is that a program known as a REPL is provided
• REPL stands for
  • Read
  • Evaluate
  • Print
  • Loop
• This allows scripting languages to be used interactively

Comparison between Scripting and "Systems" Languages¶

• These are generalizations

Ousterhout, John K. "Scripting: Higher level programming for the 21st century." Computer 31.3 (1998): 23-30.

Reasons to prefer scripting or systems languages¶

• The application requires a GUI
• The application involves a lot of string manipulation
• The application needs to use a variety of pre-existing components
• New features need to be added very quickly and frequently

Ousterhout, John K. "Scripting: Higher level programming for the 21st century." Computer 31.3 (1998): 23-30.

Popular Applications¶

• System Administration
• Text Manipulation
• Web Development
  • Front-end/Client-side
  • Back-end/Sever-side
• Graphical User Interfaces

Popular Applications¶

• Protyping
• Automation
• Hacking
• Gluing
  • Using two or more existing programs together

Famous Projects Using Scripting Languages¶

• Bash
  • Parts of Git
• R
  • Many internal data analytics in large companies
  • Many Graphics and analysis on 538.com and NYT's the Upshot
• JavaScript
  • Atom Text Editor
  • Practically Every Website

Famous Projects Using Scripting Languages (Part 2)¶

• PHP
  • Wordpress
  • Facebook
  • Wikipedia
• Ruby
  • Homebrew
  • Jekyll

How This Class Will Help You Get a Job¶

• Web Development
  • Client Side Scripting
  • Server Side Scripting
• SysAdmin
  • Backups
  • Networks
  • Logfile Rotation

How This Class Will Help You Get a Job¶

• Computer Security
  • Automated Testing
  • Logfile Inspection
• Software Development
  • Automated Testing
  • Prototyping
  • Cross-Platform Code

How This Class Will Help You Get a Job¶

• Research
  • Access to existing libraries
  • Gluing existing code in multiple languages
  • Can share your code easily

Language Tour: Perl¶

sub fibRec {
    my $n = shift;
    $n < 2 ? $n : fibRec($n - 1) + fibRec($n - 2);
}

https://rosettacode.org/wiki/Fibonacci_sequence#Perl

Language Tour: Perl¶

print join('.', split /,/, 'Hello,How,Are,You,Today'), "\n";

http://rosettacode.org/wiki/Tokenize_a_string#Perl

Language Tour: Bash¶

fib() {
  local n=$1
  [ $n -lt 2 ] && echo -n $n || echo -n $(( $( fib $(( n - 1 )) ) + $( fib $(( n - 2 )) ) ))
}

https://rosettacode.org/wiki/Fibonacci_sequence#UNIX_Shell

Language Tour: Bash¶

string='Hello,How,Are,You,Today'

(IFS=,
 printf '%s.' $string
 echo)

http://rosettacode.org/wiki/Tokenize_a_string#UNIX_Shell

Language Tour: R¶

recfibo <- function(n) {
  if ( n < 2 ) n
  else Recall(n-1) + Recall(n-2)
}

https://rosettacode.org/wiki/Fibonacci_sequence#R

Language Tour:¶

text <- "Hello,How,Are,You,Today"
junk <- strsplit(text, split=",")
print(paste(unlist(junk), collapse="."))

http://rosettacode.org/wiki/Tokenize_a_string#R

Language Tour: JavaScript¶

function fib(n) {
  return n<2?n:fib(n-1)+fib(n-2);
}

https://rosettacode.org/wiki/Fibonacci_sequence#JavaScript

Language Tour: JavaScript¶

alert( "Hello,How,Are,You,Today".split(",").join(".") );

http://rosettacode.org/wiki/Tokenize_a_string#JavaScript

Language Tour: PHP¶

<?php
function fibRec($n) {
    return $n < 2 ? $n : fibRec($n-1) + fibRec($n-2);
}
?>

https://rosettacode.org/wiki/Fibonacci_sequence#PHP

Language Tour: PHP¶

<?php
$str = 'Hello,How,Are,You,Today';
echo implode('.', explode(',', $str));
?>

http://rosettacode.org/wiki/Tokenize_a_string#PHP

Jupyter¶

• Lectures this semester are prepared using a tool called Jupyter
  • Allows mixing of code and notes
  • Kernels available for many languges
• Following Examples from http://r-statistics.co/Complete-Ggplot2-Tutorial-Part1-With-R-Code.html

Binder¶

• Binder uses a combination of Jupyter and related projects along with Docker to create a cloud based notebook
• Anyone can run with the link, creates a virtual machine per session
  • Nothing is saved in the virtual machine permanetly
• A great way to try out lectures interactively, or explore what small changes to the code will do