std::time::Instant - Rust
Description: API documentation for the Rust `Instant` struct in crate `std`.
Keywords: rust, rustlang, rust-lang, Instant

# 1.8.0[−][src]Struct std::time::Instant

    pub struct Instant(_);

A measurement of a monotonically nondecreasing clock. Opaque and useful only with `Duration`.

Instants are always guaranteed to be no less than any previously measured instant when created, and are often useful for tasks such as measuring benchmarks or timing how long an operation takes.

Note, however, that instants are not guaranteed to be steady. In other words, each tick of the underlying clock may not be the same length (e.g. some seconds may be longer than others). An instant may jump forwards or experience time dilation (slow down or speed up), but it will never go backwards.

Instants are opaque types that can only be compared to one another. There is no method to get "the number of seconds" from an instant. Instead, it only allows measuring the duration between two instants (or comparing two instants).

The size of an `Instant` struct may vary depending on the target operating system.

Example:

    use std::time::{Duration, Instant};
    use std::thread::sleep;

    fn main() {
       let now = Instant::now();

       // we sleep for 2 seconds
       sleep(Duration::new(2, 0));
       // it prints '2'
       println!("{}", now.elapsed().as_secs());
    }

Run

# OS-specific behaviors

An `Instant` is a wrapper around system-specific types and it may behave differently depending on the underlying operating system. For example, the following snippet is fine on Linux but panics on macOS:

    use std::time::{Instant, Duration};

    let now = Instant::now();
    let max_nanoseconds = u64::MAX / 1_000_000_000;
    let duration = Duration::new(max_nanoseconds, 0);
    println!("{:?}", now + duration);

Run

# Underlying System calls

Currently, the following system calls are being used to get the current time using `now()`:

Platform | System call
--- | ---
CloudABI | clock_time_get (Monotonic Clock)
SGX | `insecure_time` usercall. More information on timekeeping in SGX
UNIX | clock_gettime (Monotonic Clock)
Darwin | mach_absolute_time
VXWorks | clock_gettime (Monotonic Clock)
WASI | __wasi_clock_time_get (Monotonic Clock)
Windows | QueryPerformanceCounter

Disclaimer: These system calls might change over time.

## Implementations

### `impl Instant`[src]

#### `pub fn now() -> Instant`[src]

Returns an instant corresponding to "now".

# Examples

    use std::time::Instant;

    let now = Instant::now();

Run

#### `pub fn duration_since(&self, earlier: Instant) -> Duration`[src]

Returns the amount of time elapsed from another instant to this one.

# Panics

This function will panic if `earlier` is later than `self`.

# Examples

    use std::time::{Duration, Instant};
    use std::thread::sleep;

    let now = Instant::now();
    sleep(Duration::new(1, 0));
    let new_now = Instant::now();
    println!("{:?}", new_now.duration_since(now));

Run

#### `pub fn checked_duration_since(&self, earlier: Instant) -> Option<Duration>`1.39.0[src]

Returns the amount of time elapsed from another instant to this one, or None if that instant is later than this one.

# Examples

    use std::time::{Duration, Instant};
    use std::thread::sleep;

    let now = Instant::now();
    sleep(Duration::new(1, 0));
    let new_now = Instant::now();
    println!("{:?}", new_now.checked_duration_since(now));
    println!("{:?}", now.checked_duration_since(new_now)); // None

Run

#### `pub fn saturating_duration_since(&self, earlier: Instant) -> Duration`1.39.0[src]

Returns the amount of time elapsed from another instant to this one, or zero duration if that instant is later than this one.

# Examples

    use std::time::{Duration, Instant};
    use std::thread::sleep;

    let now = Instant::now();
    sleep(Duration::new(1, 0));
    let new_now = Instant::now();
    println!("{:?}", new_now.saturating_duration_since(now));
    println!("{:?}", now.saturating_duration_since(new_now)); // 0ns

Run

#### `pub fn elapsed(&self) -> Duration`[src]

Returns the amount of time elapsed since this instant was created.

# Panics

This function may panic if the current time is earlier than this instant, which is something that can happen if an `Instant` is produced synthetically.

# Examples

    use std::thread::sleep;
    use std::time::{Duration, Instant};

    let instant = Instant::now();
    let three_secs = Duration::from_secs(3);
    sleep(three_secs);
    assert!(instant.elapsed() >= three_secs);

Run

#### `pub fn checked_add(&self, duration: Duration) -> Option<Instant>`1.34.0[src]

Returns `Some(t)` where `t` is the time `self + duration` if `t` can be represented as `Instant` (which means it's inside the bounds of the underlying data structure), `None` otherwise.

#### `pub fn checked_sub(&self, duration: Duration) -> Option<Instant>`1.34.0[src]

Returns `Some(t)` where `t` is the time `self - duration` if `t` can be represented as `Instant` (which means it's inside the bounds of the underlying data structure), `None` otherwise.

## Trait Implementations

### `impl Add<Duration> for Instant`[src]

#### `type Output = Instant`

The resulting type after applying the `+` operator.

#### `fn add(self, other: Duration) -> Instant`[src]

# Panics

This function may panic if the resulting point in time cannot be represented by the underlying data structure. See `Instant::checked_add` for a version without panic.

### `impl AddAssign<Duration> for Instant` 1.9.0[src]

#### `fn add_assign(&mut self, other: Duration)`[src]

Performs the `+=` operation. Read more

### `impl Clone for Instant`[src]

#### `fn clone(&self) -> Instant`[src]

Returns a copy of the value. Read more

#### `fn clone_from(&mut self, source: &Self)`1.0.0[src]

Performs copy-assignment from `source`. Read more

### `impl Copy for Instant`[src]

### `impl Debug for Instant`[src]

#### `fn fmt(&self, f: &mut Formatter<'_>) -> Result`[src]

Formats the value using the given formatter. Read more

### `impl Eq for Instant`[src]

### `impl Hash for Instant`[src]

#### `fn hash<__H: Hasher>(&self, state: &mut __H)`[src]

Feeds this value into the given `Hasher`. Read more

#### `fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,` 1.3.0[src]

Feeds a slice of this type into the given `Hasher`. Read more

### `impl Ord for Instant`[src]

#### `fn cmp(&self, other: &Instant) -> Ordering`[src]

This method returns an `Ordering` between `self` and `other`. Read more

#### `#[must_use]fn max(self, other: Self) -> Self`1.21.0[src]

Compares and returns the maximum of two values. Read more

#### `#[must_use]fn min(self, other: Self) -> Self`1.21.0[src]

Compares and returns the minimum of two values. Read more

#### `#[must_use]fn clamp(self, min: Self, max: Self) -> Self`[src]

🔬 This is a nightly-only experimental API. (`clamp` #44095)

Restrict a value to a certain interval. Read more

### `impl PartialEq<Instant> for Instant`[src]

#### `fn eq(&self, other: &Instant) -> bool`[src]

This method tests for `self` and `other` values to be equal, and is used by `==`. Read more

#### `fn ne(&self, other: &Instant) -> bool`[src]

This method tests for `!=`.

### `impl PartialOrd<Instant> for Instant`[src]

#### `fn partial_cmp(&self, other: &Instant) -> Option<Ordering>`[src]

This method returns an ordering between `self` and `other` values if one exists. Read more

#### `fn lt(&self, other: &Instant) -> bool`[src]

This method tests less than (for `self` and `other`) and is used by the `<` operator. Read more

#### `fn le(&self, other: &Instant) -> bool`[src]

This method tests less than or equal to (for `self` and `other`) and is used by the `<=` operator. Read more

#### `fn gt(&self, other: &Instant) -> bool`[src]

This method tests greater than (for `self` and `other`) and is used by the `>` operator. Read more

#### `fn ge(&self, other: &Instant) -> bool`[src]

This method tests greater than or equal to (for `self` and `other`) and is used by the `>=` operator. Read more

### `impl StructuralEq for Instant`[src]

### `impl StructuralPartialEq for Instant`[src]

### `impl Sub<Duration> for Instant`[src]

#### `type Output = Instant`

The resulting type after applying the `-` operator.

#### `fn sub(self, other: Duration) -> Instant`[src]

Performs the `-` operation. Read more

### `impl Sub<Instant> for Instant`[src]

#### `type Output = Duration`

The resulting type after applying the `-` operator.

#### `fn sub(self, other: Instant) -> Duration`[src]

Performs the `-` operation. Read more

### `impl SubAssign<Duration> for Instant` 1.9.0[src]

#### `fn sub_assign(&mut self, other: Duration)`[src]

Performs the `-=` operation. Read more

## Auto Trait Implementations

### `impl RefUnwindSafe for Instant`

### `impl Send for Instant`

### `impl Sync for Instant`

### `impl Unpin for Instant`

### `impl UnwindSafe for Instant`

## Blanket Implementations

### `impl<T> Any for T where
T: 'static + ?Sized,` [src]

#### `fn type_id(&self) -> TypeId`[src]

Gets the `TypeId` of `self`. Read more

### `impl<T> Borrow<T> for T where
T: ?Sized,` [src]

#### `fn borrow(&self) -> &Tⓘ

### Notable traits for &'_ mut F

`impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W`
`[src]

Immutably borrows from an owned value. Read more

### `impl<T> BorrowMut<T> for T where
T: ?Sized,` [src]

#### `fn borrow_mut(&mut self) -> &mut Tⓘ

### Notable traits for &'_ mut F

`impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized, '_> Read for &'_ mut Rimpl<W: Write + ?Sized, '_> Write for &'_ mut W`
`[src]

Mutably borrows from an owned value. Read more

### `impl<T> From<T> for T`[src]

#### `fn from(t: T) -> T`[src]

Performs the conversion.

### `impl<T, U> Into<U> for T where
U: From<T>,` [src]

#### `fn into(self) -> U`[src]

Performs the conversion.

### `impl<T> ToOwned for T where
T: Clone,` [src]

#### `type Owned = T`

The resulting type after obtaining ownership.

#### `fn to_owned(&self) -> T`[src]

Creates owned data from borrowed data, usually by cloning. Read more

#### `fn clone_into(&self, target: &mut T)`[src]

🔬 This is a nightly-only experimental API. (`toowned_clone_into` #41263)

recently added

Uses borrowed data to replace owned data, usually by cloning. Read more

### `impl<T, U> TryFrom<U> for T where
U: Into<T>,` [src]

#### `type Error = Infallible`

The type returned in the event of a conversion error.

#### `fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>`[src]

Performs the conversion.

### `impl<T, U> TryInto<U> for T where
U: TryFrom<T>,` [src]

#### `type Error = <U as TryFrom<T>>::Error`

The type returned in the event of a conversion error.

#### `fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>`[src]

Performs the conversion.