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rubyshellcommand-lineargvgets

Ruby gets method throws an exception when arguments are passed from the console

I have experienced some ODD behavior from the code below:

require 'CSV'

$DEBUG = ARGV.empty? ? false : ARGV[0] #Global debug flag.

class PhoneBook
  #class code here etc etc
end

PhoneBook.start_dir = "file-io-samples/phonebooks/"
puts "Enter a phonebook!"
name = gets #This is the problem.
puts "Using #{name}.."

When I pass true to have $DEBUG set to true on execution I get an error from name = gets and I have no idea why. If I don't pass parameters via the command line everything works fine.

This is the error output:

C:\Pickaxe>ruby PhoneBook.rb
Enter a phonebook!
Hurrah! Works
Using Hurrah! Works
..

C:\Pickaxe>ruby PhoneBook.rb true
Enter a phonebook!
Exception `Errno::ENOENT' at PhoneBook.rb:62 - No such file or directory - true
PhoneBook.rb:62:in `gets': No such file or directory - true (Errno::ENOENT)
        from PhoneBook.rb:62:in `gets'
        from PhoneBook.rb:62:in `<main>'

C:\Pickaxe>

If I need to I can post the class definition, but I don't think it's part of the problem.

Solution

  • gets reads from stdin if no arguments are passed, and from the file that was passed as an argument otherwise. You are passing an argument true, ergo gets tries to read from a file named true, which apparently doesn't exist.

    This is the very first sentence of the documentation of gets:

    Returns (and assigns to $_) the next line from the list of files in ARGV (or $*)