Format std::time output

问题:

I want to display the current time in a certain format.

I am trying to avoid the time crate since it's flagged as deprecated on its the GitHub repo.

I want to use this exact format time::now().strftime("%Y-%m-%d][%H:%M:%S").unwrap() using std::time, but it doesn't seems to have a strftime.

回答1:

There are (currently) two now methods: Instant::now and SystemTime::now.

Instant says:

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

SystemTime says:

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

Neither of these is truly appropriate for showing to a human. Time is hard, and formatting time is additional complexity. It's really a good thing that it's not part of the standard library, otherwise it would have a fixed API that couldn't be improved.

As mentioned elsewhere, I'd recommend using chrono, the heir apparent to the time crate.

回答2:

You can use the crate chrono to achieve the same result:

extern crate chrono;

use chrono::Local;

fn main() {
    let date = Local::now();
    println!("{}", date.format("%Y-%m-%d][%H:%M:%S"));
}

Edit:

The time crate is not deprecated: it is unmaintained.

Besides, it is not possible to format a time using only the standard library.