Question

From what I have read ARGV should be a constant since it is all uppercase, but I was able to write a quick program that changed one of the values in ARGV without error. So what type of variable is ARGV?

p ARGV
ARGV[0] = "Not the orginal"
p ARGV

Answer 1

ARGV is a constant, but it’s an Array. Values in a constant array can be freely changed without any warnings, like any usual array element.

irb(main)> ARGV.class
=> Array
irb(main)> QWERTY = [1, 2, 3, 4]
=> [1, 2, 3, 4]
irb(main)> QWERTY[1] = 5
=> 5
irb(main)> QWERTY
=> [1, 5, 3, 4]
irb(main)> QWERTY << 6
=> [1, 5, 3, 4, 6]
irb(main)> QWERTY = 3
(irb): warning: already initialized constant QWERTY
=> 3