Get the value of an environment variable

envvar_get() returns the value of an environment variable.

envvar_get_oneof() gets the value of an environment variable and ensures that it is within a defined set of potential values.

Usage

envvar_get(
  x,
  default = NULL,
  transform = NULL,
  validate = NULL,
  warn_default = TRUE
)

envvar_get_oneof(
  x,
  choices,
  default = NULL,
  transform = NULL,
  validate = NULL,
  warn_default = TRUE
)

Arguments

x: String containing an environment variable name
default: Optional default value if the environment variable is not set
transform: Optional function that applies a transformation to the variable's value
validate: Optional function that checks a value for validity
warn_default: Show a warning if the default value is used (default: TRUE)
choices: A list containing the potential values

Value

The value of the given environment variable, if set. This is a string unless a transform function has changed the object's type.

Details

envvar_get() and the other type-specific variants follow this workflow:

The value of the environment variable is retrieved. If that variable is not set and default non-NULL, the default value is used. Otherwise an error is raised.
Optionally, the value can be transformed by a function specified by the transform argument. Transformation functions return a scalar object.
Optionally, the value can be validated by a function specified by the validate argument. Validation functions return a logical value indicating whether or not the value matches the given criteria. An error is raised if the validation function does not return TRUE.
The transformed, validated value is returned.

Examples

# Get the current user's home directory
envvar_get("HOME")
#> [1] "/home/runner"

# Get the current logging level for your app, ensuring it is a known value
envvar_set("LOG_LEVEL" = "DEBUG")
envvar_get_oneof(
  "LOG_LEVEL",
  choices = c("TRACE", "DEBUG", "INFO", "SUCCESS", "WARN", "ERROR", "FATAL")
)
#> [1] "DEBUG"