#!/usr/bin/env python
# coding: utf-8

# # How to Read Remote Files?
# 
# Not only local ROOT files can be read, but also remote ones. The right *TFile* specialisation is chosen at runtime automatically by ROOT. The reccomended way of accessing remote files is to use the *TFile::Open* static function:

# In[1]:


auto myFile = TFile::Open("http://root.cern.ch/files/usa.root")


# In this case, ROOT automatically recognised from the string "http://" that the class to be used was TWebFile and chose the right plugin.
# This technique can be applied to a variety of protocols, such as for files on:
# + **EOS**: TFile::Open("root://eosatlas.cern.ch//eos/atlas/user/t/test/histo.root");
# + **Web**: TFile::Open("http://root.cern.ch/files/usa.root");
# + **Amazon S3**: TFile::Open("s3://s3-eu-west-1.amazonaws.com/roots3/hsimple.root");
# + **Google Storage**: TFile::Open("gs://commondatastorage.googleapis.com/roots3/hsimple.root");
# 
# ## Authenticate on Amazon S3
# Here follows a step-by-step recipe for authentication configuration between ROOT and Amazon S3:
# + Go to the main Amazon S3 website and login into your account.
# + Once you are logged in, click on Security Credentials on the left panel.
# + In the section Access Credentials, tab Access Keys retrieve both Access Key ID and Secret Access Key.
# + Set the following two environment variables: S3_ACCESS_KEY="your access key id" and S3_SECRET_KEY="your secret access key"
# 
# ## Authenticate on Google Storage
# Here follows a step-by-step recipe for authentication configuration between ROOT and Google Storage:
# + Enable Legacy Access for Google Storage.
# + Once you have generated both Legacy Storage Access Keys, retrieve both Access Key and Secret.
# + Set the following two environment variables: GS_ACCESS_ID="your access id" and GS_ACCESS_KEY="your access secret key"