What does %w(array) mean?

%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.

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

There are other % literals:

• %r() is another way to write a regular expression.
• %q() is another way to write a single-quoted string (and can be multi-line, which is useful)
• %Q() gives a double-quoted string
• %x() is a shell command
• %i() gives an array of symbols (Ruby >= 2.0.0)
• %s() turns foo into a symbol (:foo)

I don't know any others, but there may be some lurking around in there...

There is also %s that allows you to create any symbols, for example:

%s|some words|          #Same as :'some words'
%s[other words]         #Same as :'other words'
%s_last example_        #Same as :'last example'

Since Ruby 2.0.0 you also have:

%i( a b c )   # => [ :a, :b, :c ]
%i[ a b c ]   # => [ :a, :b, :c ]
%i_ a b c _   # => [ :a, :b, :c ]
# etc...