fadvise.go

// +build linux

package main

import (
	"io"
	"os"

	"golang.org/x/sys/unix"
)

// POSIX_FADV_DONTNEED should be defined by the golang.org/x/sys/unix package, but isn't.
const POSIX_FADV_DONTNEED = 4

func main() {
	filename := os.Args[1]

	f, err := os.Create(filename)
	if err != nil {
		panic(err)
	}

	_, err = io.Copy(f, os.Stdin)
	if err != nil {
		panic(err)
	}

	err = f.Sync()
	if err != nil {
		panic(err)
	}

	err = unix.Fadvise(int(f.Fd()), 0, 0, POSIX_FADV_DONTNEED)
	if err != nil {
		panic(err)
	}

	err = f.Close()
	if err != nil {
		panic(err)
	}
}