Jeff-Russ

Study: Bash fails: splitting strings

Jeff-Russ

Shell lib: Mostly String Manipulation Functions

Jeff-Russ

Shell lib: String I/O Functions

---

fancyprompt for bash

A fancy 'are you sure' style shell prompt

fancyprompt take at least two args, the prompt message and produces an 'are you
sure' style prompt with a timeout of 10 sec and option to cancel with 'c'.
The first arg is always the message as a string (accepts \n \t etc). And the
remaining args are function names that are called depending on the result.

Jeff-Russ

Study: Bash Scope Test

Observe bash's scoping in action with variables declared:

1. inside and outside of functions,
2. in various orders and
3. with and without the local keyword

Jeff-Russ

getreturn() {
	command -v "$*" >/dev/null 2>&1 || { 
		echo >&2
		return 127;
	}
	typeset cmnd="$*"
	typeset ret_code
	eval $cmnd >/dev/null 2>&1
	ret_code=$?
	return $ret_code

Jeff-Russ

#!/bin/bash

ask_yn() {
	# Adapted from http://djm.me/ask by Jeff-Russ
	if   [ "${2:-}" = "Y" ]; then prompt="Y/n"; default=Y
	elif [ "${2:-}" = "N" ]; then prompt="y/N"; default=N
	else                          prompt="y/n"; default=
	fi

	while true; do # keeps repeating the question until it gets a valid answer.

Jeff-Russ

Study: Bash Variable Quoting

Bash is designed to automatically reinterpret where one argument ends and a new one begins based on whitespace unless the string is surrounded by double quotes. It's because Bash is so string-centric that you can call a script or function like this:

some_func John Doe "age 24"

and all of those argument will be interpreted as string literals, not variable name or command names. It's because all you can pass is strings that you can omit the quotes. Even when you pass a variable, it needs to be expanded to a string via $ before being passed. If you omit the quotes around "age 24", however, the arg count will increase to four.

Inside the function you have a similar situation. Even if the last arg is passed in with double quotes you can run into

Jeff-Russ

Run (almost) Any Language From a Bash Script

You probably know that when you make a bash script you give it a shebang like one of these:

#!/bin/sh
#!/bin/bash
#!/usr/local/bin/bash 
#!/usr/bin/env bash

Jeff-Russ

#!/usr/bin/env ruby

# Example of Recursion in Ruby: Simplifying a Fraction


########## non-recursive version: #########

def findGcd (a, b)
  while b != 0 do

Jeff-Russ

JS Objects vs Ruby Hashes

Ruby has iterators baked right in for all of it's containers:

whatever.each do |variable|
  # code
end

You can do this with Ruby arrays, hashes, objects, etc but in Javascript you don't have this most of the time. You have it for arrays but when you want something like an associative array your go-to is a Javascript object literal you pretend is an associate array by just not putting methods in: