In Go language, io packages supply fundamental interfaces to the I/O primitives. And its principal job is to enclose the ongoing implementations of such king of primitives. The MultiWriter() function in Go language is used to create a writer that copies its writes to each and every given writers, which is the same as the Unix command tee(1). Here, each and every write is written to each of the included writer, one by one. Moreover, this function is defined under the io package. Here, you need to import the “io” package in order to use these functions.
Syntax:
func MultiWriter(writers ...Writer) Writer
Here, “writers” is the number of writers stated as a parameter in this function.
Return value: It returns a Writer which includes the number of bytes present in the stated buffer and also returns an error if any. And if a stated writer returns an error then the entire write operation ceases and doesn’t extend down the list.
Example 1:
// Golang program to illustrate the usage of // io.MultiWriter() function // Including main package package main // Importing fmt, io, bytes, and strings import ( "bytes"
"fmt"
"io"
"strings"
) // Calling main func main() { // Defining reader using NewReader method
reader := strings.NewReader( "Geeks" )
// Defining two buffers
var buffer1, buffer2 bytes.Buffer
// Calling MultiWriter method with its parameters
writer := io.MultiWriter(&buffer1, &buffer2)
// Calling Copy method with its parameters
n, err := io.Copy(writer, reader)
// If error is not nil then panics
if err != nil {
panic(err)
}
// Prints output
fmt.Printf( "Number of bytes in the buffer: %v\n" , n)
fmt.Printf( "Buffer1: %v\n" , buffer1.String())
fmt.Printf( "Buffer2: %v\n" , buffer2.String())
} |
Output:
Number of bytes in the buffer: 5 Buffer1: Geeks Buffer2: Geeks
Here, Copy() method is used to return the number of bytes contained in the buffer. And here the content of both the buffer is the same as the stated writer duplicates its write to all the other writers.
Example 2:
// Golang program to illustrate the usage of // io.MultiWriter() function // Including main package package main // Importing fmt, io, bytes, and strings import ( "bytes"
"fmt"
"io"
"strings"
) // Calling main func main() { // Defining reader using NewReader method
reader := strings.NewReader( "GeeksforGeeks\nis\na\nCS-Portal!" )
// Defining two buffers
var buffer1, buffer2 bytes.Buffer
// Calling MultiWriter method with its parameters
writer := io.MultiWriter(&buffer1, &buffer2)
// Calling Copy method with its parameters
n, err := io.Copy(writer, reader)
// If error is not nil then panics
if err != nil {
panic(err)
}
// Prints output
fmt.Printf( "Number of bytes in the buffer: %v\n" , n)
fmt.Printf( "Buffer1: %v\n" , buffer1.String())
fmt.Printf( "Buffer2: %v\n" , buffer2.String())
} |
Output:
Number of bytes in the buffer: 29 Buffer1: GeeksforGeeks is a CS-Portal! Buffer2: GeeksforGeeks is a CS-Portal!