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// Copyright (c) 2019 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package atomicfile contains code related to writing to filesystems
// atomically.
//
// This package should be considered internal; its API is not stable.
package atomicfile // import "tailscale.com/atomicfile"
import (
"os"
"path/filepath"
"runtime"
)
// WriteFile writes data to filename+some suffix, then renames it
// into filename. The perm argument is ignored on Windows.
func WriteFile(filename string, data []byte, perm os.FileMode) (err error) {
f, err := os.CreateTemp(filepath.Dir(filename), filepath.Base(filename)+".tmp")
if err != nil {
return err
}
tmpName := f.Name()
defer func() {
if err != nil {
f.Close()
os.Remove(tmpName)
}
}()
if _, err := f.Write(data); err != nil {
return err
}
if runtime.GOOS != "windows" {
if err := f.Chmod(perm); err != nil {
return err
}
}
if err := f.Sync(); err != nil {
return err
}
if err := f.Close(); err != nil {
return err
}
return os.Rename(tmpName, filename)
}
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