rust-by-practice/en/src/formatted-output/println.md

println! and format!

Printing is handled by a series of [macros][macros] defined in [std::fmt][fmt] some of which include:

• format!: write formatted text to [String][string]
• print!: same as format! but the text is printed to the console (io::stdout).
• println!: same as print! but a newline is appended.
• eprint!: same as format! but the text is printed to the standard error (io::stderr).
• eprintln!: same as eprint!but a newline is appended.

All parse text in the same fashion. As a plus, Rust checks formatting correctness at compile time.

format!

1.🌟

fn main() {
    let s1 = "hello";
    /* Fill in the blank */
    let s = format!(__);
    assert_eq!(s, "hello, world!");
}

print!, println!

2.🌟

fn main() {
   /* Fill in the blanks to make it print:
   Hello world, I am 
   Sunface!
   */
   __("hello world, ");
   __("I am");
   __("Sunface!");
}