Variables

User-defined variables let you share values across multiple steps without repeating yourself. Define them once under the top-level vars: key, then reference them with ${var_name} in any command.

Static Variables

A plain string value, available for interpolation:

vars:
  app_name: "bivvy"
  deploy_target: "production"

steps:
  greet:
    command: "echo Setting up ${app_name} for ${deploy_target}"

Computed Variables

Use command: to run a shell command at the start of a workflow. The command’s stdout (trimmed) becomes the variable value:

vars:
  version:
    command: "cat VERSION"
  git_sha:
    command: "git rev-parse --short HEAD"

steps:
  tag:
    command: "echo Deploying ${version} (${git_sha})"

Computed variables run once when the workflow starts, not once per step. If a computed variable’s command exits non-zero, the workflow fails immediately with an error naming the variable.

Mixing Static and Computed

vars:
  app_name: "myapp"
  version:
    command: "grep '^version' Cargo.toml | head -1 | cut -d'\"' -f2"

steps:
  build:
    command: "docker build -t ${app_name}:${version} ."
  push:
    command: "docker push ${app_name}:${version}"

Resolution Priority

When the same name exists in multiple sources, Bivvy resolves it using this priority order (highest to lowest):

1. Prompt values from the current run
2. Saved preferences from previous runs
3. User-defined variables (vars:)
4. Environment variables
5. Built-in variables (project_name, project_root, bivvy_version)

This means a prompt answer always wins over a vars: definition, and a vars: definition wins over an environment variable with the same name.

Escaping

Use $${ to output a literal ${ without interpolation:

steps:
  example:
    command: "echo '$${NOT_INTERPOLATED}'"  # outputs: ${NOT_INTERPOLATED}