fmt.Fprintf() Function in Golang With Examples

Last Updated : 25 Apr, 2025

In Go language, fmt package implements formatted I/O with functions analogous to C’s printf() and scanf() function. The fmt.Fprintf() function in Go language formats according to a format specifier and writes to w. 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 Fprintf(w io.Writer, format string, a ...interface{}) (n int, err error)

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

w io.Writer: This is the specified standard input or output.
format string: This is containing some strings including verbs.
a …interface{}: This is the specified constant variables used in the code.

Return Value: It returns the number of bytes written and any write error encountered.
Example 1:

C

// Golang program to illustrate the usage of
// fmt.Fprintf() function
 
// Including the main package
package main
 
// Importing fmt and os
import (
    "fmt"
    "os"
)
 
// Calling main
func main() {
 
    // Declaring some const variables
    const name, dept = "GeeksforGeeks", "CS"
 
    // Calling Fprintf() function which returns
    // "n" as the number of bytes written and 
    // "err" as any error ancountered
    n, err := fmt.Fprintf(os.Stdout, "%s is a %s portal.\n",
                                                name, dept)
 
    // Printing the number of bytes written
    fmt.Print(n, " bytes written.\n")
 
    // Printing if any error encountered
    fmt.Print(err)
 
}

Output:

GeeksforGeeks is a CS portal.
30 bytes written.
<nil>

Example 2:

C

// Golang program to illustrate the usage of
// fmt.Fprintf() function
 
// Including the main package
package main
 
// Importing fmt and os
import (
    "fmt"
    "os"
)
 
// Calling main
func main() {
 
    // Declaring some const variables
    const num1, num2, num3 = 5, 10, 15
 
    // Calling Fprintf() function which returns
    // "n" as the number of bytes written and 
    // "err" as any error encountered
    n, err := fmt.Fprintf(os.Stdout, "%d + %d = %d.\n",
                                      num1, num2, num3)
 
    // Printing the number of bytes written
    fmt.Print(n, " bytes written.\n")
 
    // Printing if any error encountered
    fmt.Print(err)
 
}

Output:

5 + 10 = 15.
13 bytes written.
<nil>

fmt.Fprint() Function in Golang With Examples

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