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lookup(inputMap, key, default) retrieves the value associated with key in inputMap. If the key does not exist, default is returned.

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Signature

lookup(inputMap map, key string, default any) any

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Example

Look up environment-specific database URLs from a map, falling back to a local development URL: 
variable "env" {
  description = "Target deployment environment"
  type        = string
  default     = "development"
}

computed "db_url" {
  description = "Database URL for the target environment"
  expression  = lookup({
    staging    = "postgres://db.staging.internal/app"
    production = "postgres://db.prod.internal/app"
  }, var.env, "postgres://localhost/app_dev")
}

task "migrate" {
  description = "Run database migrations"
  commands    = ["./bin/migrate --db ${computed.db_url}"]
}
For development (or any unknown environment), the fallback postgres://localhost/app_dev is used.

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Notes

  • lookup also works on objects, looking up attribute values by name.
  • If you need a hard failure when a key is missing (rather than a fallback), access the map directly with bracket notation: map[key].
  • default must be compatible with the map’s value type.