siddontang.golib/ioutil2/ioutil.go

// Copyright 2012, Google Inc. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package ioutil2

import (
	"io"
	"io/ioutil"
	"os"
	"path"
)

// Write file to temp and atomically move when everything else succeeds.
func WriteFileAtomic(filename string, data []byte, perm os.FileMode) error {
	dir, name := path.Dir(filename), path.Base(filename) 
	f, err := ioutil.TempFile(dir, name)
	if err != nil {
		return err
	}
	n, err := f.Write(data)
	f.Close()
	if err == nil && n < len(data) {
		err = io.ErrShortWrite
	} else {
		err = os.Chmod(f.Name(), perm)
	}
	if err != nil {
		os.Remove(f.Name())
		return err
	}
	return os.Rename(f.Name(), filename)
}

// Check file exists or not
func FileExists(name string) bool {
	_, err := os.Stat(name)
	return !os.IsNotExist(err)
}