Assume Role ruby SDK. Assume role and call specific sdk method using commandline opts.

assume_role_creds.rb

#!/usr/bin/env ruby

require 'rubygems'
require 'optparse'
require 'aws-sdk-core'
require 'pry'

options = {}

OptionParser.new do |opts|
  opts.banner = "Usage: assume_role_creds-rb [options]"

  opts.on("--rolearn ROLE", "define the account delegation role arn, eg. arn:aws:iam::99999999:root") do |value|
    options[:role_arn] = value
  end

  opts.on("--session SESSION", "specify a name for the elevated session, eg. Develop") do |value|
    options[:session] = value
  end

  opts.on("--region REGION", "specify the AWS region, e.g. us-west-2") do |value|
    options[:region] = value
  end

  opts.on("--apiclient API", "specify the api you would like to work with. ex. ec2, dynamodb") do |value|
    options[:api] = value
  end

  opts.on("-h", "--help") do
    puts opts
    exit
  end
end.parse!

role_arn = options[:role_arn]
role_session_name = options[:session]
aws_region = options[:region]
api = []

assumed_creds = Aws::AssumeRoleCredentials.new(client: Aws::STS::Client.new(region: aws_region), role_arn: role_arn, role_session_name: role_session_name)

if options[:api] == 'ec2'
  ec2api = Aws::EC2::Client.new(region: aws_region, credentials: assumed_creds)
  ec2api.pry
end

if options[:api] == 'dynamodb'
  dynamoapi = Aws::DynamoDB::Client.new(region: aws_region, credentials: assumed_creds)
  dynamoapi.pry
end