Struct EnvVar 

pub struct EnvVar {
    pub name: &'static str,
    pub kind: EnvKind,
    pub owner: Owner,
    pub default: &'static str,
    pub summary: &'static str,
}

One environment variable the reader reads.

Fields

name: &'static str

The variable name as it appears in the environment.

kind: EnvKind

What the value means and how it is parsed.

owner: Owner

Who owns the value space.

default: &'static str

What happens when the variable is unset.

summary: &'static str

One line an embedder can read to know whether they care.

Implementations

impl EnvVar

pub fn is_set(&self) -> bool

Read this variable as a boolean, using the semantics it declares.

Panics

If the variable is not declared as a flag. That is a programming error in the reader, caught by an_unset_flag_matches_its_declared_default, not something a value in the environment can cause.

impl EnvVar

pub fn count_or(&self, default: usize) -> usize

Read this variable as a count, falling back to default.

A value that is not a number is not a smaller number: it is a mistake, and the default is a better answer than a silently-wrong one.

pub fn millis_or(&self, default: Duration) -> Duration

Read this variable as a millisecond duration, falling back to default.

pub fn port(&self) -> Option<u16>

Read this variable as a port number, if it names one.

pub fn is_present(&self) -> bool

Whether the variable is present at all, whatever its value – including empty or 0.

Several older switches are read this way, and narrowing them to recognised spellings would turn =0 from “on” into “off” for anyone who already relies on it. It is a method rather than an EnvKind variant because EnvKind is public and exhaustive: adding a variant would break a downstream match in a 4.x release.

pub fn text(&self) -> Option<String>

Read this variable as text, if it is set to anything.

pub fn os(&self) -> Option<OsString>

Read this variable exactly as the host wrote it.

Unlike EnvVar::path an empty value is still Some: some readers have always treated VAR= as set, and this keeps them doing so.

pub fn string(&self) -> Option<String>

Read this variable as Unicode exactly as written, empty included.

None when unset or not valid Unicode, matching std::env::var.

pub fn path(&self) -> Option<PathBuf>

Read this variable as a path, if it is set to anything.

Takes the value as the host wrote it: a path that is not valid Unicode is still a path, and lossily repairing it would point somewhere else.

Trait Implementations

impl Clone for EnvVar

fn clone(&self) -> EnvVar

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for EnvVar

impl Debug for EnvVar

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.