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CLI

The Prefab CLI provides powerful tools for creating, modifying, and getting information about your configuration and flags.

Installation​

On a system with Node version 18+, run

npm install -g @prefab-cloud/prefab

Usage​

See prefab --help for all the available commands. prefab [COMMAND] --help will give you detailed information about a given command.

prefab is designed for humans first, but all commands support a --json flag to output JSON instead.

Providing your API Key​

You must export PREFAB_API_KEY or provide your API key via the --api-key=XYZ flag.

Using the 1password cli for your API key

To use the 1password cli for this, you can do the following (replace the op://... with the secret reference for your API key).

prefab --api-key=(op read "op://Private/Prefab API KEY/credential")

change-default​

prefab change-default NAME allows you to change the default value for an environment. Any rules defined for that environment will still apply; only the default is changed.

This can be particularly helpful for flipping a flag on or off for everyone.

Example:

prefab change-default my.flag.name --value=true --environment=staging

create​

prefab create NAME creates a new flag or config in Prefab. You can use this to create basic values, encrypted secrets, or values provided by ENV vars.

Example: prefab create my.new.string --type string --value="hello world" --secret

download​

prefab download will download a datafile for a given environment. Datafiles are helpful for offline testing, CI, and running your own JS/React endpoint with the serve command.

Example:

prefab download --environment=test

get​

prefab get NAME will give you the value for a config in the environment tied to your API key.

Example: prefab get aws.bucket

Interpolating a value from Prefab​

Since the CLI is a well-behaved citizen of the command line, you can use it to compose other commands.

Here's an example command to download a file from s3 using the aws cli. Prefab values are interpolated for the aws key and bucket name.

aws s3api get-object \
  --bucket $(prefab get aws.bucket) \
  --key $(prefab get aws.db.backup.filename) \
  db.tgz

As you'd expect, you can similarly use prefab in a pipeline with xargs and similar.

info​

prefab info NAME will show details about an item in Prefab. Example output:

prefab info aws.bucket

https://app.cloud/account/projects/XYZ/configs/aws.bucket

- Default: false
- Staging: true
- Production: [see rules] https://app.cloud/account/projects/XYZ/configs/aws.bucket?environment=588

Evaluations over the last 24 hours:

Production: 34,789
- 33% - false
- 67% - true

Staging: 17,138
- 100% - true

Development: 7
- 100% - false

list​

prefab list will show the names of items in your Prefab account. You can pass flags to filter this to only show items of a specific type (e.g. segments).

override​

prefab override lets you override the value for a config or feature flag for your prefab.cloud user. This is especially helpful for testing both sides of a feature flag.

Are you using a backend key for your server code and a frontend key for your UI? No problem; this override will apply to any environment using an API key created by your prefab.cloud user.

Example: prefab override my.flag.name --value=true

serve​

prefab serve will start a local server to serve up a local datafile that React and JS clients can talk to. See prefab download for more.

prefab serve prefab.test.588.config.json
Server is listening on 3099. Press ctrl-c to stop.

Example Dockerfile

FROM node:20
WORKDIR /app
RUN npm i -g @prefab-cloud/prefab
COPY prefab.Production.589.config.json /app
ENV PREFAB_LOCAL_ONLY=true
EXPOSE 9898
CMD prefab serve prefab.Production.589.config.json --port=9898