Getting started
Escape
Escape Inventory

 Input Variables

Our Hello World package from the previous section is a beautiful piece of engineering:

name: quickstart/hello-world
version: 0.0.@
description: 
logo: 

includes:
- README.md

build: hello_world.sh
deploy: hello_world.sh

When we deploy our package it greets the world, but our Product Manager wants our package to greet the Universe when we deploy to production.

This kind of thing happens a lot, even in less contrived examples; we often have configuration that changes depending on what environment it’s being deployed in.

In our Escape plan we can make these configuration variables explicit and define them as inputs:

name: quickstart/hello-world
version: 0.0.@
description: 
logo: 

includes:
- README.md

build: hello_world.sh
deploy: hello_world.sh

inputs:
- who

When we try and run a build or deployment step Escape will now start complaining:

$ escape run build   
Build: Starting build.
Build: Error: Missing value for variable 'who'

Defining input variables makes Escape expect a value for both builds and deployments. We can scope variables to specific phases, add type checks, a description, defaults, and all sorts of stuff, but we’ll keep ours simple for now:

name: quickstart/hello-world
version: 0.0.@
description: 
logo: 

includes:
- README.md

build: hello_world.sh
deploy: hello_world.sh

inputs:
- id: who
  default: World
  type: string
  description: Who should we be greeting?

Because we’ve set a default value Escape will use this when we don’t specify one ourselves:

$ escape run build
Build: Running build step /home/bspaans/src/workspace/escape/hello_world.sh.
Build: hello_world.sh: Hello World!
Build: ✔️ Completed build

The next step is to update our hello_world.sh script to use the new variable. Variables are passed into build scripts by their id (in this case “who” – we know it should be “whom”, don’t email in) and receive the INPUT_ prefix. This is a complicated way to say that we should update our script:

cat > hello_world.sh <<EOF
#!/bin/bash

set -euf

echo "Hello \${INPUT_who}!"
EOF

And just like that we’ve made our build and deployment configurable:

$ escape run build -v who=You
Build: Running build step /home/bspaans/src/workspace/escape/hello_world.sh.
Build: hello_world.sh: Hello You!
Build: ✔️ Completed build

Inputs are stored in the Escape state, which means we don’t have to set the input again on the next run:

$ escape run build           
Build: Running build step /home/bspaans/src/workspace/escape/hello_world.sh.
Build: hello_world.sh: Hello You!
Build: ✔️ Completed build

We will find out more about the state in the next session as we try to deploy our package to multiple environments, but let’s release our progress first:

escape run release