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This is an extension for node's fs.writeFile that makes its operation atomic and allows you set ownership (uid/gid of the file).

var writeFileAtomic = require('write-file-atomic')
writeFileAtomic(filename, data, [options], callback)

  • filename String
  • data String | Buffer
  • options Object
    • chown Object
      • uid Number
      • gid Number
    • encoding String | Null default = 'utf8'
    • fsync Boolean default = true
    • mode Number default = 438 (aka 0666 in Octal)
    • Promise Object default = native Promise object callback Function

Atomically and asynchronously writes data to a file, replacing the file if it already exists. data can be a string or a buffer.

The file is initially named filename + "." + murmurhex(__filename,, ++invocations). If writeFile completes successfully then, if passed the chown option it will change the ownership of the file. Finally it renames the file back to the filename you specified. If it encounters errors at any of these steps it will attempt to unlink the temporary file and then pass the error back to the caller. If multiple writes are concurrently issued to the same file, the write operations are put into a queue and serialized in the order they were called, using Promises. Native promises are used by default, but you can inject your own promise-like object with the Promise option. Writes to different files are still executed in parallel.

If provided, the chown option requires both uid and gid properties or else you'll get an error.

The encoding option is ignored if data is a buffer. It defaults to 'utf8'.

If the fsync option is false, writeFile will skip the final fsync call.


writeFileAtomic('message.txt', 'Hello Node', {chown:{uid:100,gid:50}}, function (err) {
  if (err) throw err;
  console.log('It\'s saved!');

var writeFileAtomicSync = require('write-file-atomic').sync
writeFileAtomicSync(filename, data, [options])

The synchronous version of writeFileAtomic.