What does %w(array) mean?

Question

I'm looking at the documentation for FileUtils.

I'm confused by the following line:

FileUtils.cp %w(cgi.rb complex.rb date.rb), '/usr/lib/ruby/1.6' 

What does the %w mean? Can you point me to the documentation?

Answer 1

I think of %w() as a "word array" - the elements are delimited by spaces and it returns an array of strings.

Here are all % literals:

• %w() array of strings
• %r() regular expression.
• %q() string
• %x() a shell command (returning the output string)
• %i() array of symbols (Ruby >= 2.0.0)
• %s() symbol
• %() (without letter) shortcut for %Q()

The delimiters ( and ) can be replaced with a lot of variations, like [ and ], |, !, etc.

When using a capital letter %W() you can use string interpolation #{variable}, similar to the " and ' string delimiters. This rule works for all the other % literals as well.

abc = 'a b c' %w[1 2#{abc} d] #=> ["1", "2\#{abc}", "d"] %W[1 2#{abc} d] #=> ["1", "2a b c", "d"] 

Answer 2

%w(foo bar) is a shortcut for ["foo", "bar"]. Meaning it's a notation to write an array of strings separated by spaces instead of commas and without quotes around them. You can find a list of ways of writing literals in zenspider's quickref.