envvar_get {envvar} | R Documentation |
Get the value of an environment variable
Description
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: |
choices |
A list containing the potential values |
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 returnTRUE
.The transformed, validated value is returned.
Value
The value of the given environment variable, if set. This is a string
unless a transform
function has changed the object's type.
Examples
# Get the current user's home directory
envvar_get("HOME")
# 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")
)