fmt.Fscanf() Function in Golang With Examples

In Go language, fmt package implements formatted I/O with functions analogous to C’s printf() and scanf() function. The fmt.Fscanf() function in Go language scans the specified text, read from r and then stores the successive space-separated values into successive arguments as determined by the format. Here newlines in the input must match newlines in the format. Moreover, this function is defined under the fmt package. Here, you need to import the “fmt” package in order to use these functions.

Syntax:

func Fscanf(r io.Reader, format string, a ...interface{}) (n int, err error)

Parameters: This function accepts three parameters which are illustrated below:

• r io.Reader: This parameter contains the scanned specified texts.
• format string: This parameter contains different formats for receiving the elements.
• a …interface{}: This parameter is the specified variable for each elements.

Returns: It returns the number of items successfully parsed.

Example 1:

// Golang program to illustrate the usage of
// fmt.Fscanf() function

// Including the main package
package main

// Importing fmt, io and strings
import (
    "fmt"
    "os"
    "strings"
)

// Calling main
func main() {

        // Declaring some type of variables
    var (
        i int
        b bool
        s string
    )

    // Calling the NewReader() function to
    // specify some type of texts.
    // variable "r" contains the scanned texts
    r := strings.NewReader("10 false GFG")

    // Calling the Fscanf() function to receive
    // the scanned texts
    n, err := fmt.Fscanf(r, "%d %t %s", &i, &b, &s)

    // If the above function returns an error then
    // below statement will be executed
    if err != nil {
        fmt.Fprintf(os.Stderr, "Fscanf: %v\n", err)
    }

    // Printing each type of scanned texts
    fmt.Println(i, b, s)

    // It returns the number of items
    // successfully scanned
    fmt.Println(n)
}

Output:

10 false GFG
3

Example 2:

// Golang program to illustrate the usage of
// fmt.Fscanf() function

// Including the main package
package main

// Importing fmt, io and strings
import (
    "fmt"
    "os"
    "strings"
)

// Calling main
func main() {

        // Declaring some type of variables
    var (
        i int
        b bool
        s string
        f float32
    )

    // Calling the NewReader() function to
    // specify some type of texts.
    // variable "r" contains the scanned texts
    r := strings.NewReader("46 true 3.4 GeeksforGeeks")

    // Calling the Fscanf() function to receive
    // the scanned texts
    n, err := fmt.Fscanf(r, "%d %t %g %s", &i, &b, &f, &s)

    // If the above function returns an error then
    // below statement will be executed
    if err != nil {
        fmt.Fprintf(os.Stderr, "Fscanf: %v\n", err)
    }

    // Printing each type of scanned texts
    fmt.Println(i, b, f, s)

    // It returns the number of items
    // successfully scanned
    fmt.Println(n)
}

Output:

46 true 3.4 GeeksforGeeks
4