how to store a Ruby array into a file?

I am not sure what exactly you want, but, to serialize an array, write it to a file and read back, you can use this:

fruits = %w{mango banana apple guava}
=> ["mango", "banana", "apple", "guava"]
serialized_array = Marshal.dump(fruits)
=> "\004\b[\t\"\nmango\"\vbanana\"\napple\"\nguava"
File.open('/tmp/fruits_file.txt', 'w') {|f| f.write(serialized_array) }
=> 33
# read the file back
fruits = Marshal.load File.read('/tmp/fruits_file.txt')
=> ["mango", "banana", "apple", "guava"]

There are other alternatives you can explore, like json and YAML.

To just dump the array to a file in the standard [a,b,c] format:

require 'pp'
$stdout = File.open('path/to/file.txt', 'w')
pp myArray

That might not be so helpful, perhaps you might want to read it back? In that case you could use json. Install using rubygems with gem install json.

require 'rubygems'
require 'json'
$stdout = File.open('path/to/file.txt', 'w')
puts myArray.to_json

Read it back:

require 'rubygems'
require 'json'
buffer = File.open('path/to/file.txt', 'r').read
myArray = JSON.parse(buffer)

Some standard options for serializing data in Ruby:

• Marshal
• YAML
• JSON (built-in as of 1.9, various gems available as well)

(There are other, arguably better/faster implementations of YAML and JSON, but I'm linking to built-ins for a start.)

In practice, I seem to see YAML most often, but that may not be indicative of anything real.

Here's a quick yaml example

config = {"rank" => "Admiral", "name"=>"Akbar",
          "wallet_value" => 9, "bills" => [5,1,1,2]}

open('store.yml', 'w') {|f| YAML.dump(config, f)}
loaded = open('store.yml') {|f| YAML.load(f) }
p loaded 
# => {"name"=>"Akbar", "wallet_value"=>9,  \
#  "bills"=>[5, 1, 1,   2], "rank"=>"Admiral"}

Example: write text_area to a file where text_area is an array of strings.

File.open('output.txt', 'w') { |f| text_area.each { |line| f << line } }

Don't forget to do error checking on file operations :)

Afaik.. files contain lines not arrays. When you read the files, the data can then be stored in an array or other data structures. I am anxious to know if there is another way.