Printing

Node.js's console.log writes to stdout, and console.error writes to stderr. Go splits this into clearer functions: fmt.Println prints with a trailing newline, fmt.Printf takes a C-style format string, and fmt.Fprintf writes to any io.Writer — including os.Stderr. Rust has equivalent macros (println!/eprint!) built into the language; Swift only has a plain print, so it needs Foundation for C-style formatting and for writing to stderr; Java 25 adds IO.println for compact source files, while System.err still works as before.

Printing to stdout and stderr

console.log('print to stdout')
console.log('format %s %d', 'example', 1)
console.error('print to stderr')

package main
 
import (
	"fmt"
	"os"
)
 
func main() {
	fmt.Println("print to stdout")
	fmt.Printf("format %s %v\n", "example", 1)
	fmt.Fprintf(os.Stderr, "print to stderr")
}

fn main() {
    println!("print to stdout");
    println!("format {} {}", "example", 1);
    eprint!("print to stderr");
}

import Foundation
 
print("print to stdout")
print(String(format: "format \("example") %d", 1))
FileHandle.standardError.write(Data("print to stderr".utf8))

void main() {
    IO.println("print to stdout");
    IO.println("format %s %d".formatted("example", 1));
    System.err.print("print to stderr");
}

print to stdout
format example 1
print to stderr