serverless/docs/understanding-serverless/serverless-variables.md

Serverless Variables

The Serverless framework provides a powerful variable system to give your serverless.yml configuration file extra flexibility. With Serverless Variables, you'll be able to do the following:

• Reference & load variables from environment variables
• Reference & load variables from CLI options
• Recursively reference properties of any type from the same serverless.yml file

Referencing Environment Variables

To reference environment variables, you'll need to use the ${env.SOME_VAR} syntax in your serverless.yml configuration file. Here's an example:

service: new-service
provider: aws
functions:
  hello:
      name: ${env.FUNC_PREFIX}-hello
      handler: handler.hello
  world:
      name: ${env.FUNC_PREFIX}-world
      handler: handler.world
  

In the previous example you're dynamically adding a prefix to the function names by referencing the FUNC_PREFIX env var. So you can easily change that prefix for all functions by changing the FUNC_PREFIX env var.

Referencing CLI Options

To reference CLI options that you passed, you'll need to use the ${opt.some_option} syntax in your serverless.yml configuration file. Here's an example:

service: new-service
provider: aws
functions:
  hello:
      name: ${opt.stage}-hello
      handler: handler.hello
  world:
      name: ${opt.stage}-world
      handler: handler.world
  

In the previous example you're dynamically adding a prefix to the function names by referencing the stage option that you pass in the CLI. So when you deploy, the function name will always include the stage you're deploying to.

Referencing CLI Options

To reference CLI options that you passed, you'll need to use the ${opt.some_option} syntax in your serverless.yml configuration file. Here's an example:

service: new-service
provider: aws
custom:
  globalSchedule: rate(10 minutes)
    
functions:
  hello:
      name: ${opt.stage}-hello
      handler: handler.hello
      events:
        - schedule: ${self.custom.globalSchedule}
  world:
      name: ${opt.stage}-world
      handler: handler.world
      events:
        - schedule: ${self.custom.globalSchedule}
  

In the previous example you're setting a global schedule for all functions by referencing the globalSchedule property in the same serverless.yml file. This way, you can easily change the schedule for all functions whenever you like.