Symbols are so frequently used as hash key that Ruby 1.9 introduces a new syntax you can use name: value pairs to create a hash if the key are symbols:
inst_section = {
cello: 'sting',
clarinet: 'woodwind',
drum: 'Programming'
}
puts "An oboe is a #{inst_section[:cello]}"
produces:
An oboe is a sting
Command-line Arguments:
when you run a ruby program from the command line, you can pass in arguments.These are accessible in two different ways.
First.the array ARGV contains each if the arguments passed to the running program.Create a file called cmd_line.rb that contains the following:
puts "You gave #{ARGV.size} arguments"
p ARGV when we run it with arguments,we can see that they get passed in:
$ ruby cmd_line.rb ant bee cat dog *produces*
You gave 4 arguments
["ant","bee","cat","dog"] Often,the agruments to a program are the names of files that you want to process.In this case, you can use a second technique: the variable ARGF is a special kind of I/O object that acts like all the contents of all the files whose names are passed on the Command line.