Setting up a REST client

Before we start exploring the APIs, we need a REST client to interface with these services. So, here are two REST clients and how you can set them up.

Setting up cURL

cURL is a command line tool for making HTTP requests. Since Cloud Vision API is accessed over REST, we can use curl as a client for it. You can download cURL for your OS from here: https://curl.haxx.se/download.html. You can test the installation by running the following command: 

$ curl --version
curl 7.50.0 (x86_64-apple-darwin15.4.0) libcurl/7.50.0 OpenSSL/1.0.2h zlib/1.2.8
Protocols: dict file ftp ftps gopher http https imap imaps pop3 pop3s rtsp smb smbs smtp smtps telnet tftp
Features: IPv6 Largefile NTLM NTLM_WB SSL libz TLS-SRP UnixSockets

To test whether cURL is working as expected, run the following command:

$ curl https://reqres.in/api/users

This hits a public-hosted free mock REST API service named Req | Res (https://reqres.in/) and will return a bunch of users. Your output should look something...