fmt.Scan() / Scanf() / Scanln()

import "fmt"

// Reads values separated by spaces or newlines.
n, err := fmt.Scan(&var1, &var2)

// Reads values according to a format string.
n, err := fmt.Scanf("format string", &var1, &var2)

// Reads values from a single line (newline acts as the delimiter).
n, err := fmt.Scanln(&var1, &var2)

// Return values:
// n   — number of items successfully read
// err — error (e.g., io.EOF)

package main

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

func main() {
    // Using fmt.Sscan to read values from a string (used here as a runnable example).
    // In a real program, use fmt.Scan instead.

    // Scan: reads multiple values separated by spaces.
    var name string
    var age int
    input := "Yamada 30"
    fmt.Sscan(input, &name, &age) // reads from a string (for testing)
    fmt.Printf("Name: %s, Age: %d\n", name, age)

    // Scanf: reads values using a format string.
    var x, y float64
    fmt.Sscanf("3.14 2.72", "%f %f", &x, &y)
    fmt.Printf("x=%.2f, y=%.2f\n", x, y)

    // Scanln: reads values from a single line.
    var word1, word2 string
    fmt.Sscanln("Hello World", &word1, &word2)
    fmt.Printf("word1=%s, word2=%s\n", word1, word2)

    fmt.Println()

    // For real CLI input, bufio.Scanner is recommended (it can read a full line including spaces).
    scanner := bufio.NewScanner(strings.NewReader("Go Dictionary\n"))
    if scanner.Scan() {
        fmt.Println("Line read:", scanner.Text())
    }

    // To read from standard input (uncomment to use):
    // scanner := bufio.NewScanner(os.Stdin)
    // fmt.Print("Input: ")
    // if scanner.Scan() {
    //     line := scanner.Text()
    //     fmt.Println("Received:", line)
    // }

    _ = os.Stdin // suppress unused import error
}

The fmt.Scan() family of functions is well-suited for reading simple values, but struggles with strings that contain spaces (such as full names). To read an entire line, it is common practice to use bufio.NewScanner(os.Stdin). In competitive programming, combining bufio.NewReader(os.Stdin) with fmt.Fscan() for faster input is also a widely used pattern.

Be careful with how newlines ('\n') are handled in the format string of fmt.Scanf(). Input containing Windows-style line endings (\r\n) can cause unexpected behavior. For production CLI tools, using bufio.Scanner is recommended.

For output functions such as fmt.Println(), see fmt.Println() / Printf(). For buffered I/O, see io.Reader / Writer / bufio.