Ruby ARGV array search

Question

I am having some issues searching for what options have been passed in the ARGV. I have,

if ARGV.include? '-v' == true
    puts "Do junk"
else
    puts "Nope"
end

This seems like a shockingly simple thing but I always get "Nope" either when I place "-v" or when I do not. Am I missing something simple here?

Answer 1

I don know if it's your problem, but you don't need the == true.

if ARGV.include? '-v'
  puts "Do junk"
else
  puts "Nope"
end

The include? method returns true or false.

Answer 2

Why are you searching ARGV for options? Use the standard library's OptionParser class, which is made for this.

require 'optparse'
require 'pp'

options = {}
OptionParser.new { |opt|
  opt.on('-v', '--verbose', 'Be verbose') { |o| options[:verbose] = o }
}.parse!

pp options

Save that, and run it with something like: ruby test.rb -v or ruby test.rb --verbose and you'll see:

{:verbose=>true}

Run it with ruby test.rb -h or ruby test.rb --help and you'll see:

Usage: test [options]
    -v, --verbose                    Be verbose

OptionParser has all sorts of nice (and intelligent) tricks for setting booleans, required parameters, coercing values so you can get multiple values for a parameter returned as an array, etc. And, notice that it created the help for me, including using -h or --help for the flag.

Look at the examples in the documentation for additional ideas of what it can do.

Answer 3

This is a precedence problem. Write as'

if ARGV.include?('-v') == true
  puts "Do junk"
else
  puts "Nope"
end

In your case if ARGV.include? '-v' == true has been interpreted as if ARGV.include? ('-v' == true). Now '-v' == true returns false, and false is not included in your ARGV array, so if evaluates as false, and else part is getting executed.

Better to write as

if ARGV.include? '-v'
  puts "Do junk"
else
  puts "Nope"
end

Because ARGV is an array, and Array#include?(ob) returns true, if the ob found inside the array.

Answer 4

All of the other answers so far are right in that it's a precedence problem.

Here are a couple helpful notes, the first of which has already been touched on:

1. You don't need == true, since the include? method already returns true or false.

2. For parsing command-line arguments, you might find it more intuitive to use a library like Trollop. Using Trollop, your example could be done like this:

   require 'trollop'
   opts = Trollop::options do
     opt :verbose, "Run verbosely"  # (-v is created automatically from this)
   end
   
   if opts[:v] 
     puts "yes" 
   else
     puts "no"
   end
   

(EDIT: See also the Tin Man's answer re: optparse)