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// Package atomicfile provides the ability to write a file with an eventual
// rename on Close (using os.Rename). This allows for a file to always be in a
// consistent state and never represent an in-progress write.
//
// NOTE: `os.Rename` may not be atomic on your operating system.
package atomicfile
import (
"io/ioutil"
"os"
"path/filepath"
)
// File behaves like os.File, but does an atomic rename operation at Close.
type File struct {
*os.File
path string
}
// New creates a new temporary file that will replace the file at the given
// path when Closed.
func New(path string, mode os.FileMode) (*File, error) {
f, err := ioutil.TempFile(filepath.Dir(path), filepath.Base(path))
if err != nil {
return nil, err
}
if err := os.Chmod(f.Name(), mode); err != nil {
f.Close()
os.Remove(f.Name())
return nil, err
}
return &File{File: f, path: path}, nil
}
// Close the file replacing the configured file.
func (f *File) Close() error {
if err := f.File.Close(); err != nil {
os.Remove(f.File.Name())
return err
}
if err := os.Rename(f.Name(), f.path); err != nil {
return err
}
return nil
}
// Abort closes the file and removes it instead of replacing the configured
// file. This is useful if after starting to write to the file you decide you
// don't want it anymore.
func (f *File) Abort() error {
if err := f.File.Close(); err != nil {
os.Remove(f.Name())
return err
}
if err := os.Remove(f.Name()); err != nil {
return err
}
return nil
}
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