git.giacomolli.uk - onechat/blob - file.go

   1 package main
   2
   3 import (
   4         "errors"
   5         "fmt"
   6         "os"
   7         "path/filepath"
   8 )
   9
  10 // writeFileAtomic replaces the file at path with data through a temporary file
  11 // and a rename. A reader or a crash of the process sees the old file or the new
  12 // file, never a part of one.
  13 func writeFileAtomic(path string, data []byte) error {
  14         file, err := os.CreateTemp(filepath.Dir(path), "."+filepath.Base(path)+".*")
  15         if err != nil {
  16                 return fmt.Errorf("create temporary file: %w", err)
  17         }
  18
  19         _, err = file.Write(data)
  20         err = errors.Join(err, file.Close())
  21         if err == nil {
  22                 err = os.Rename(file.Name(), path)
  23         }
  24
  25         if err != nil {
  26                 return errors.Join(fmt.Errorf("replace file: %w", err), os.Remove(file.Name()))
  27         }
  28
  29         return nil
  30 }