Publish a local file to an AWS S3 bucket (make it public, give it a URL).

publish_to_s3.rb

require 'aws-sdk'
require 'yaml'

CONFIG_FILE_NAME = 'aws-config.txt'

def do_confirm(phrase)
  print "#{phrase} (Y/N): "
  # you *must* use $stdin with gets if you have command-line arguments.
  # Otherwise, gets receives streaming input and doesn't wait for the terminal.
  a = $stdin.gets.strip.downcase
  return a == 'y'
end

# make sure the user entered:
# 1. a file to publish
# 2. the bucket to publish it in.
if ARGV.count != 2
   puts "Usage: publish_to_s3 <file> <s3_bucket+path>"
   puts "Both arguments are required!"
   exit
end

# get the args. The `bucket_name` arg might have an object appended to it after
# the first slash character...
file_name, bucket_name = ARGV

# split the bucket name after the first slash character. Anything afterward is
# considered the S3 object name.
bucket_name, object_name = bucket_name.split('/', 2)

# make sure that `file_name` refers to an actual file...
unless File.exists?(file_name)
  puts "** local file does not exist: #{file_name}"
  exit
end

# if no object name was provided (appended to the bucket name after '/'), then
# use the file name as the object name. We'll publish the file with the same
# name that it has on the local file system.
if object_name.nil?
  object_name = File.basename(file_name)
end

# Load aws-config.txt to see if there are AWS credentials there.
#
# We're expecting a YAML-formatted file like this:
#
#     ---
#     access_key_id:     ACCESSKEYID
#     secret_access_key: SECRETACCESKEY
#
begin
  config_file = File.open(CONFIG_FILE_NAME) { |f| f.read }
  options = YAML.load(config_file)
  AWS.config(options)
rescue
  puts "** Hmmm, no config file (#{CONFIG_FILE_NAME})!"
  # without setting AWS credentials specifically, the AWS SDK will try to load
  # them from the environment variables. Check the environment variables, just
  # to make sure...
  if ENV['AWS_ACCESS_KEY_ID'].nil? or ENV['AWS_SECRET_ACCESS_KEY'].nil?
    puts "** No AWS access information in environment, either. Aborting!"
    exit
  end
end

# Create a new S3 object
s3 = AWS::S3.new

s3bucket = s3.buckets[bucket_name]

unless s3bucket.exists?
  puts "** Bucket \"#{bucket_name}\" does not exist on S3!"
  exit unless do_confirm("Do you want me to create it?")
end

puts "publishing:"
puts "  #{file_name}"
puts "  -> S3://#{bucket_name}/#{object_name}"

exit unless do_confirm("OK?")

# does the object already exist? If so, we should update it. If not, we'll
# create a new object.

s3obj = s3bucket.objects[object_name]

if s3obj.exists?
  puts "** updating existing object"
else
  puts "** creating new object"
end

print "** writing object... "
s3obj.write(File.new(file_name, 'rb').read)
puts "complete!"
s3obj.acl = :public_read
puts "** object has public_read access"
public_url = s3obj.public_url({:secure => false})

puts "You can now access your object with the URL:"
puts "  #{public_url}"