Go Scan
last modified April 11, 2024
In this article we show how to read standard input in Golang with scan functions. The scan functions are located in the fmt package.
$ go version go version go1.22.2 linux/amd64
We use Go version 1.22.2.
Scan functions
There are three scan functions: scan, scanln, and
scanf.
func Scan(a ...any) (n int, err error)
The scan function scans text read from standard input and stores
successive space-separated values into given arguments. A newline character
counts as space. This means that we can continue writing input arguments after
we pressed Enter.
func Scanln(a ...any) (n int, err error)
The Scanln is similar to Scan, but stops scanning at a newline.
Ffter the final item there must be a newline or EOF.
func Scanf(format string, a ...any) (n int, err error)
The Scanf function reads from standard input and storing successive
space-separated values into the given arguments, as determined by the string
format. It returns the number of items successfully scanned. The function allows
more sophisticated scanning.
Go Scan
In the first example, we use the Scan function.
package main
import (
"fmt"
"log"
)
func main() {
var name string
fmt.Print("Enter your name: ")
_, err := fmt.Scan(&name)
if err != nil {
log.Fatal(err)
}
fmt.Printf("Hello %s!\n", name)
}
The example reads an input from a user, builds a message and prints it to the console.
$ go run main.go Enter your name: Peter Hello Peter!
package main
import (
"fmt"
"log"
)
func main() {
var name string
var age int
fmt.Print("Enter your name and age: ")
n, err := fmt.Scan(&name, &age)
if err != nil {
log.Fatal(err)
}
fmt.Printf("scanned %d arguments\n", n)
fmt.Printf("%s is %d years old\n", name, age)
}
We scan two arguments. We print the number of scanned arguments and a message built from these two arguments.
$ go run main.go Enter your name and age: Peter 23 scanned 2 arguments Peter is 23 years old
Go Scanln
With Scanln, the newline character terminates the scanning process.
package main
import (
"fmt"
"log"
)
func main() {
var name1 string
var name2 string
var name3 string
fmt.Print("Enter three names: ")
_, err := fmt.Scanln(&name1, &name2, &name3)
if err != nil {
log.Fatal(err)
}
fmt.Printf("Entered names: %s, %s, %s\n", name1, name2, name3)
}
We use the Scanln function to read three names.
Go Scanf
The Scanf function enables more advanced scanning.
package main
import (
"fmt"
"log"
)
func main() {
var n1, n2, n3, n4, n5 int
fmt.Print("Enter five numbers separated by comma and space: ")
_, err := fmt.Scanf("%d, %d, %d, %d, %d", &n1, &n2, &n3, &n4, &n5)
if err != nil {
log.Fatal(err)
}
sum := n1 + n2 + n3 + n4 + n5
fmt.Printf("The sum of five numbers is: %d\n", sum)
}
In this example, we read five numbers. The numbers have to be separated by a comma and a space character.
$ go run main.go Enter five numbers separated by comma and space: 1, 2, 3, 4, 5 The sum of five numbers is: 15
Source
In this article we have worked with the scan functions in Golang.
Author
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