Write more than 4K bytes to StdinPipe.

WriteBytesToStdinPipe.go

package main

import (
	"bytes"
	"fmt"
	"log"
	"os/exec"
	"io"
)

func main() {
	cmd := exec.Command("less")

	pype, err := cmd.StdinPipe()
	if err != nil {
		log.Fatal(err)
	}

	bytes4k := generateBytes(1024 * 4)
	fmt.Println("bytes generated.")

	go writeBytes(pype, bytes4k)
	// writeBytes(pype, bytes4k) // Can't write. Write is locked.

	err = cmd.Run()
	if err != nil {
		log.Fatal(err)
	}

	fmt.Println("finished.")
}

func generateBytes(num int) []byte {
	byte := bytes.NewBuffer(make([]byte, 0, num))
	for i := 0; i < num; i++ {
		byte.WriteByte('0')
	}
	return byte.Bytes()
}

func writeBytes(in io.WriteCloser, bytes []byte) {
	defer in.Close()

	_, err := in.Write(bytes)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println("written bytes to pipe.")

	_, err = in.Write([]byte{'0'})
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println("written 1 byte to pipe.")
}