---
title: "DeGAUSS Metadata Specifications"
output: rmarkdown::html_vignette
vignette: >
  %\VignetteIndexEntry{DeGAUSS Metadata Specifications}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
---

## Metadata Elements

The below list contains the names of supported metadata elements captured using environment variables defined using `ENV` instructions inside the Dockerfile:

- **`degauss_name`**: name of DeGAUSS container (use only lower case letters and underscores)
- **`degauss_version`**: version number corresponding to GitHub release and latest version of container available from the GitHub Container Registry
- **`degauss_description`**: a short (< 50 characters) description that finishes the sentence "This container returns ..."
- **`degauss_argument`**: name and default value of any argument `short argument description [default: x]`

## Defining Metadata Environment Variables in the Dockerfile

- The template Dockerfile from {dht} (`dht::use_degauss_dockerfile()`) comes with the above four (but with commented out `ENV` instructions for specifying an optional command line argument)
- Each `ENV` must be on its own line and only define one variable at a time
- In general, any `ENV` instruction that begins with `degauss_` can/will be read in by `dht::get_degauss_env_dockerfile()` or `dht::get_degauss_env_online()` 

### Getting Metadata About A DeGAUSS Image Online

Get information about one single DeGAUSS image:

```{r}
dht::get_degauss_env_online("fortunes")
```

or get a table of information about the images in the core library

```{r}
core_info <- dht::get_degauss_core_lib_env()
knitr::kable(core_info)
```