package main

import (
	"bytes"
	"fmt"
	"io"
	"io/ioutil"
	"os"
)

func main() {
	tmpfile, err := ioutil.TempFile("", "copy_file_range")
	if err != nil {
		fmt.Fprint(os.Stderr, err)
		os.Exit(1)
	}
	status := copy(tmpfile)
	os.Remove(tmpfile.Name())
	os.Exit(status)
}

func copy(tmpfile *os.File) int {
	cmdline, err := os.Open("/proc/self/cmdline")
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
		return 1
	}
	defer cmdline.Close()
	if _, err := io.Copy(tmpfile, cmdline); err != nil {
		fmt.Fprintf(os.Stderr, "copy failed: %v\n", err)
		return 1
	}
	if err := tmpfile.Close(); err != nil {
		fmt.Fprintln(os.Stderr, err)
		return 1
	}
	old, err := ioutil.ReadFile("/proc/self/cmdline")
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
		return 1
	}
	new, err := ioutil.ReadFile(tmpfile.Name())
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
		return 1
	}
	if !bytes.Equal(old, new) {
		fmt.Fprintf(os.Stderr, "got %q want %q\n", new, old)
		return 1
	}
	return 0
}