How to store arrays in a file in ruby?

Question

I am new to ruby. Can anyone tell me how can we store arrays in a file?

Answer 1

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.

Answer 2

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)

Answer 3

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.

Answer 4

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.

Answer 5

There are multiple ways to dump an array to disk. You need to decide if you want to serialize in a binary format or in a text format.

For binary serialization you can look at Marshal

For text format you can use json, yaml, xml (with rexml, builder, ... ) , ...

Answer 6

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"}