io.PipeReader.Read() Function in Golang with Examples
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 PipeReader.Read() function in Go language is used to implement the standard interface of the Read. It reads information from the pipe and blocks it until a writer appears or the write end of the pipe is closed. 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 (r *PipeReader) Read(data []byte) (n int, err error)
Here, “r” is a pointer to the PipeReader. Where, PipeReader is the read half of the pipe and “data” is a byte slice of specified length and the written data is read into it.
Return value: It returns the number of bytes read and an error if any. However, if the write end of the pipe is closed with an error then that error is returned as err else the err returned is an EOF error.
Example 1:
// Golang program to illustrate the usage of // io.PipeReader.Read() function // Including main package package main // Importing fmt and io import ( "fmt" "io" ) // Calling main func main() { // Calling Pipe method pipeReader, pipeWriter := io.Pipe() // Writing data to the pipe go func() { pipeWriter.Write([]byte( "GfG" )) pipeWriter.Write([]byte( "w3wiki" )) pipeWriter.Write([]byte( "GfG is a CS-Portal." )) // Closing write half of the pipe pipeWriter.Close() // Again calling Write method pipeWriter.Write([]byte( "Author!" )) }() // Defining data parameter of Read method data := make([]byte, 20) // Using for loop for i := 0; i < 3; i++ { // Calling pipeReader.Read() method n, err := pipeReader.Read(data) // If error is not nil panic if err != nil { panic(err) } // Prints the content read in buffer fmt.Printf( "%s\n" , data[:n]) // Prints number of bytes read fmt.Printf( "%v\n" , n) } } |
Output:
GfG 3 w3wiki 13 GfG is a CS-Portal. 19
Here, no error is returned as the write end of the pipe is not closed till the “for” loop runs.
Example 2:
// Golang program to illustrate the usage of // io.PipeReader.Read() function // Including main package package main // Importing fmt and io import ( "fmt" "io" ) // Calling main func main() { // Calling Pipe method pipeReader, pipeWriter := io.Pipe() // Writing data to the pipe go func() { pipeWriter.Write([]byte( "GfG" )) pipeWriter.Write([]byte( "w3wiki" )) pipeWriter.Write([]byte( "GfG is a CS-Portal." )) // Closing write half of the pipe pipeWriter.Close() // Again calling Write method pipeWriter.Write([]byte( "Author!" )) }() // Defining data parameter of Read method data := make([]byte, 20) // Using for loop for i := 0; i < 4; i++ { // Calling pipeReader.Read() method n, err := pipeReader.Read(data) // If error is not nil panic if err != nil { panic(err) } // Prints the content read in buffer fmt.Printf( "%s\n" , data[:n]) // Prints number of bytes read fmt.Printf( "%v\n" , n) } } |
Output:
GfG 3 w3wiki 13 GfG is a CS-Portal. 19 panic: EOF goroutine 1 [running]: main.main() /tmp/sandbox634835876/prog.go:43 +0x364
Here, an EOF error is returned as the write end of the pipe is closed after the third iteration of the for loop.
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