Macro `println`

#[macro_export]
macro_rules! println {
    () => { ... };
    ($($arg:tt)*) => { ... };
}

Prints to [stdout][crate::stdout], with a newline.

On all platforms, the newline is the LINE FEED character (\n/U+000A) alone (no additional CARRIAGE RETURN (\r/U+000D)).

This macro uses the same syntax as [format!], but writes to the standard output instead. See std::fmt for more information.

NOTE: The println! macro will lock the standard output on each call. If you call println! within a hot loop, this behavior may be the bottleneck of the loop. To avoid this, lock stdout with [AutoStream::lock][crate::AutoStream::lock]:

#  #[cfg(feature = "auto")] {
use std::io::Write as _;

let mut lock = anstream::stdout().lock();
writeln!(lock, "hello world").unwrap();
# }

Use println! only for the primary output of your program. Use [eprintln!] instead to print error and progress messages.

NOTE: Not all println! calls will be captured in tests like [std::println!]

Capturing will automatically be activated in test binaries
Otherwise, only when the test feature is enabled

Panics

Panics if writing to stdout fails for any reason except broken pipe.

Writing to non-blocking stdout can cause an error, which will lead this macro to panic.

Examples

#  #[cfg(feature = "auto")] {
use anstream::println;

println!(); // prints just a newline
println!("hello there!");
println!("format {} arguments", "some");
let local_variable = "some";
println!("format {local_variable} arguments");
# }