1.8.0[][src]Struct std::time::SystemTime

pub struct SystemTime(_);

A measurement of the system clock, useful for talking to external entities like the file system or other processes.

Distinct from the Instant type, this time measurement is not monotonic. This means that you can save a file to the file system, then save another file to the file system, and the second file has a SystemTime measurement earlier than the first. In other words, an operation that happens after another operation in real time may have an earlier SystemTime!

Consequently, comparing two SystemTime instances to learn about the duration between them returns a Result instead of an infallible Duration to indicate that this sort of time drift may happen and needs to be handled.

Although a SystemTime cannot be directly inspected, the UNIX_EPOCH constant is provided in this module as an anchor in time to learn information about a SystemTime. By calculating the duration from this fixed point in time, a SystemTime can be converted to a human-readable time, or perhaps some other string representation.

The size of a SystemTime struct may vary depending on the target operating system.

Example:

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

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

   // we sleep for 2 seconds
   sleep(Duration::new(2, 0));
   match now.elapsed() {
       Ok(elapsed) => {
           // it prints '2'
           println!("{}", elapsed.as_secs());
       }
       Err(e) => {
           // an error occurred!
           println!("Error: {:?}", e);
       }
   }
}Run

Methods

impl SystemTime
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An anchor in time which can be used to create new SystemTime instances or learn about where in time a SystemTime lies.

This constant is defined to be "1970-01-01 00:00:00 UTC" on all systems with respect to the system clock. Using duration_since on an existing SystemTime instance can tell how far away from this point in time a measurement lies, and using UNIX_EPOCH + duration can be used to create a SystemTime instance to represent another fixed point in time.

Examples

use std::time::SystemTime;

match SystemTime::now().duration_since(SystemTime::UNIX_EPOCH) {
    Ok(n) => println!("1970-01-01 00:00:00 UTC was {} seconds ago!", n.as_secs()),
    Err(_) => panic!("SystemTime before UNIX EPOCH!"),
}Run

Returns the system time corresponding to "now".

Examples

use std::time::SystemTime;

let sys_time = SystemTime::now();Run

Returns the amount of time elapsed from an earlier point in time.

This function may fail because measurements taken earlier are not guaranteed to always be before later measurements (due to anomalies such as the system clock being adjusted either forwards or backwards).

If successful, Ok(Duration) is returned where the duration represents the amount of time elapsed from the specified measurement to this one.

Returns an Err if earlier is later than self, and the error contains how far from self the time is.

Examples

use std::time::SystemTime;

let sys_time = SystemTime::now();
let difference = sys_time.duration_since(sys_time)
                         .expect("SystemTime::duration_since failed");
println!("{:?}", difference);Run

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

This function may fail as the underlying system clock is susceptible to drift and updates (e.g., the system clock could go backwards), so this function may not always succeed. If successful, Ok(Duration) is returned where the duration represents the amount of time elapsed from this time measurement to the current time.

Returns an Err if self is later than the current system time, and the error contains how far from the current system time self is.

Examples

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

let sys_time = SystemTime::now();
let one_sec = Duration::from_secs(1);
sleep(one_sec);
assert!(sys_time.elapsed().unwrap() >= one_sec);Run

🔬 This is a nightly-only experimental API. (time_checked_add #55940)

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

🔬 This is a nightly-only experimental API. (time_checked_add #55940)

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

Trait Implementations

impl PartialEq<SystemTime> for SystemTime
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impl Eq for SystemTime
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impl Ord for SystemTime
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Compares and returns the maximum of two values. Read more

Compares and returns the minimum of two values. Read more

impl PartialOrd<SystemTime> for SystemTime
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impl Debug for SystemTime
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impl Add<Duration> for SystemTime
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The resulting type after applying the + operator.

impl Sub<Duration> for SystemTime
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The resulting type after applying the - operator.

impl AddAssign<Duration> for SystemTime
1.9.0
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impl SubAssign<Duration> for SystemTime
1.9.0
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impl Hash for SystemTime
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Feeds a slice of this type into the given [Hasher]. Read more

impl Copy for SystemTime
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impl Clone for SystemTime
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Performs copy-assignment from source. Read more

Auto Trait Implementations

impl Send for SystemTime

impl Sync for SystemTime

Blanket Implementations

impl<T, U> TryFrom for T where
    T: From<U>, 
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🔬 This is a nightly-only experimental API. (try_from #33417)

The type returned in the event of a conversion error.

impl<T> From for T
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impl<T, U> TryInto for T where
    U: TryFrom<T>, 
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🔬 This is a nightly-only experimental API. (try_from #33417)

The type returned in the event of a conversion error.

impl<T, U> Into for T where
    U: From<T>, 
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impl<T> Borrow for T where
    T: ?Sized
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impl<T> BorrowMut for T where
    T: ?Sized
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impl<T> Any for T where
    T: 'static + ?Sized
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impl<T> ToOwned for T where
    T: Clone
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