$schemamarkup = get_post_meta(get_the_ID(), 'schemamarkup', true); if(!empty($schemamarkup)) { echo $schemamarkup; }

How to Install Postman on GNU+Linux Distros

GNU/Linux Installing Postman Guide

How to Install Postman REST/SOAP Client on GNU/Linux Distributions – Step by step Tutorials.

And Postman for Linux is the Complete API Development Environment with Integrated Tools for Every Stage of the API Lifecycle

Futhermore, you find included detailed instructions on How to Getting Started with Postman POST Request Testing on GNU/Linux.

How to Install Postman on GNU+Linux Distros

GNU/Linux Postman REST API Installation Guide