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Reading input (stdin)

Read what you type in the IDE's Input tab with fmt.Fscan or line by line with bufio.Scanner.

Runs in Zerethon IDE · Go 1.27 Official Go documentation ↗

A run cannot ask questions while it runs. Type the program's input in the Input tab before you press Run; the program reads it from os.Stdin.

main.go 
package main

import (
	"bufio"
	"fmt"
	"os"
)

func main() {
	in := bufio.NewReader(os.Stdin)
	var name string
	var a, b int
	fmt.Fscan(in, &name)
	fmt.Fscan(in, &a, &b)
	fmt.Printf("Hello, %s! %d + %d = %d\n", name, a, b, a+b)
}

Input (stdin)

Ada
3 4

Output

Hello, Ada! 3 + 4 = 7
main.go 
package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
)

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	total := 0
	for scanner.Scan() {
		line := strings.TrimSpace(scanner.Text())
		if line == "" {
			continue
		}
		n, err := strconv.Atoi(line)
		if err != nil {
			fmt.Println("skipped", line)
			continue
		}
		total += n
	}
	fmt.Println("total:", total)
}

Input (stdin)

5
10
x
15

Output

skipped x
total: 30
Reading every line until the input ends.
  • fmt.Fscan reads values separated by spaces or newlines into the variables you point it to (&name).
  • Wrap os.Stdin in one bufio.Reader and keep using it; mixing it with plain fmt.Scan loses buffered input.
  • When the input runs out, Fscan returns an error (EOF) and leaves the variables at their zero value — check its error when the input may be missing.

Related topics

Official references