Downloads all CloudWatch logs for a given lambda that have the given prefix

getCloudWatchLogs.rb

require 'json'

if (!ARGV[0] || !ARGV[1])
  puts "Usage: $ ruby getCloudWatchLogs.rb [log group name, e.g. /aws/lambda/myLambda] [log stream prefix, e.g. 2018/02/01/[123]]"
  exit
end

logGroupName = ARGV[0]
logStreamPrefix = ARGV[1]

logStreams = JSON.parse(`aws logs describe-log-streams --log-group-name #{logGroupName} --log-stream-name-prefix #{logStreamPrefix}`)

logStreams["logStreams"].map{|log| log["logStreamName"]}.each{|logname|
  output = JSON.parse(`aws logs get-log-events --log-group-name /aws/lambda/StereotypeLambda --log-stream-name #{logname}`)
  File.open("./#{logname.gsub(/\//, "_")}","w") do |f|
    output["events"].each{|e| f.write(e['message'])}
  end
}