envvar_get {envvar} | R Documentation |
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.
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
)
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 |
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.
The value of the given environment variable, if set. This is a string
unless a transform
function has changed the object's type.
# 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")
)