io.PipeWriter.Close() Function in Golang with Examples
Last Updated :
05 May, 2020
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
PipeWriter.Close() function in Go language is used to close the writer. However, successive reads from the
PipeReader i.e, read half of the pipe will not return any bytes and an EOF error is returned. 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 (w *PipeWriter) Close() error
Here, "w" is a pointer to the PipeWriter. Where PipeWriter is the write half of a pipe.
Return value: It returns the content written before Close method. And successive reads from the
PipeReader i.e read half of the pipe will not return any bytes after calling Close() method and an EOF error will be returned.
Example 1:
C
// Golang program to illustrate the usage of
// io.PipeWriter.Close() function
// Including main package
package main
// Importing fmt and io
import (
"fmt"
"io"
)
// Calling main
func main() {
// Calling Pipe method
pipeReader, pipeWriter := io.Pipe()
// Calling Close method in go function after
// two Write operations
go func() {
pipeWriter.Write([]byte("GfG"))
pipeWriter.Write([]byte("GeeksforGeeks"))
pipeWriter.Close()
// Again calling Write method
pipeWriter.Write([]byte("GfG is a CS-Portal."))
}()
// Creating buffer using make keyword
// of specified length
buffer := make([]byte, 50)
// Using for loop
for i := 0; i < 4; i++ {
// Reading the contents in buffer
n, err := pipeReader.Read(buffer)
// If error is not nil panic
if err != nil {
panic(err)
}
// Prints the content read in buffer
fmt.Printf("%s\n", buffer[:n])
}
}
GfG
GeeksforGeeks
panic: EOF
goroutine 1 [running]:
main.main()
/tmp/sandbox342418232/prog.go:42 +0x2d1
Here, the content of the two Write operations are returned as they are written before the Close() method but the content written after the Close method is not returned and an EOF error is thrown instead.
Example 2:
C
// Golang program to illustrate the usage of
// io.PipeWriter.Close() function
// Including main package
package main
// Importing fmt and io
import (
"fmt"
"io"
)
// Calling main
func main() {
// Calling Pipe method
pipeReader, pipeWriter := io.Pipe()
// Calling Close method in go function
go func() {
pipeWriter.Close()
// Calling Write method
pipeWriter.Write([]byte("GfG is a CS-Portal."))
}()
// Creating buffer using make keyword
// of specified length
buffer := make([]byte, 50)
// Using for loop
for i := 0; i < 4; i++ {
// Reading the contents in buffer
n, err := pipeReader.Read(buffer)
// If error is not nil panic
if err != nil {
panic(err)
}
// Prints the content read in buffer
fmt.Printf("%s\n", buffer[:n])
}
}
panic: EOF
goroutine 1 [running]:
main.main()
/tmp/sandbox173042396/prog.go:40 +0x2d1
Here, no Write operation is performed before Close method so no content is returned and an EOF error is thrown.