confirm.rb

#!/usr/bin/env ruby

require 'optparse'
require 'ostruct'

# The purpose of the program is to confirm if the user actually wanted to
# execute a program.
#
# Example:
#   $ confirm poweroff
#   confirm: are you sure you want to run poweroff? [Y/n]

class String
  def black;          "\033[30m#{self}\033[0m" end
  def red;            "\033[31m#{self}\033[0m" end
  def green;          "\033[32m#{self}\033[0m" end
  def brown;          "\033[33m#{self}\033[0m" end
  def blue;           "\033[34m#{self}\033[0m" end
  def magenta;        "\033[35m#{self}\033[0m" end
  def cyan;           "\033[36m#{self}\033[0m" end
  def gray;           "\033[37m#{self}\033[0m" end
end

# Splits ARGV into the options meant for confirm (like -n) and the command were
# supposed to be executing.
def split_argv argv
  arguments = Struct.new(:options, :command).new([], [])
  ignore_options = false

  for argument in argv do
    if argument == "--"
      ignore_options = true
    elsif !ignore_options && argument[0] == "-"
      arguments.options.push argument
    else
      ignore_options = true
      arguments.command.push argument
    end
  end

  return arguments
end

# Ask the user if it really want to run `command`
def verify? command, default = :yes
  hint = default == :yes ? "[Y/n]" : "[y/N]"
  print "confirm: are you sure you want to run #{command.green}? #{hint} "

  begin
    answer = STDIN.gets.strip
  rescue Interrupt
    puts
    exit 127
  end

  if answer == ''
    if default == :yes
      return true
    else
      return false
    end
  elsif answer.downcase == 'y' || answer.downcase == 'yes'
    return true
  elsif answer.downcase == 'n' || answer.downcase == 'no'
    return false
  else
    puts "please answer with 'y' or 'n'"
    return verify? command, default
  end
end

settings = Struct.new(:default).new(:yes)

optionParser = OptionParser.new do |opts|
  opts.banner = "Usage: confirm [options] command"

  opts.on "-n", "--no", "set the default to no instead of yes" do
    settings.default = :no
  end

  opts.on "-v", "--version" do
    puts "confirm 0.0.1"
    puts
    puts "Written by [REDACTED]"
    exit
  end
end

# Split the arguments
arguments = split_argv ARGV

begin
  # Parse the options that are meant for our program
  optionParser.parse(arguments.options)
rescue OptionParser::InvalidOption => e
  puts "confirm: #{e.to_s}"
  puts "Try 'confirm --help' for more information."
  exit 127
end

if arguments.command.any?
  # Ask the user if he really want to run the specified command
  if verify?(arguments.command.join(" "), settings.default)
    begin
      # Execute the specified command
      exec *arguments.command
    rescue Errno::ENOENT
      puts "confirm: command not found: #{arguments.command[0]}"
      exit 127
    end
  else
    exit 127
  end
else
  # We weren't given an command to execute, just print out the help text.
  puts optionParser.help
  exit 127
end