73 lines
3.0 KiB
Markdown
73 lines
3.0 KiB
Markdown
write-file-atomic
|
|
-----------------
|
|
|
|
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')<br>writeFileAtomic(filename, data, [options], [callback])
|
|
|
|
* filename **String**
|
|
* data **String** | **Buffer**
|
|
* options **Object** | **String**
|
|
* chown **Object** default, uid & gid of existing file, if any
|
|
* uid **Number**
|
|
* gid **Number**
|
|
* encoding **String** | **Null** default = 'utf8'
|
|
* fsync **Boolean** default = true
|
|
* mode **Number** default, from existing file, if any
|
|
* tmpfileCreated **Function** called when the tmpfile is created
|
|
* 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, process.pid, ++invocations)`.
|
|
Note that `require('worker_threads').threadId` is used in addition to `process.pid` if running inside of a worker thread.
|
|
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. 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. If **chown** is not specified it will default to using
|
|
the owner of the previous file. To prevent chown from being ran you can
|
|
also pass `false`, in which case the file will be created with the current user's credentials.
|
|
|
|
If **mode** is not specified, it will default to using the permissions from
|
|
an existing file, if any. Expicitly setting this to `false` remove this default, resulting
|
|
in a file created with the system default permissions.
|
|
|
|
If options is a String, it's assumed to be the **encoding** option. 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.
|
|
|
|
If the **tmpfileCreated** option is specified it will be called with the name of the tmpfile when created.
|
|
|
|
Example:
|
|
|
|
```javascript
|
|
writeFileAtomic('message.txt', 'Hello Node', {chown:{uid:100,gid:50}}, function (err) {
|
|
if (err) throw err;
|
|
console.log('It\'s saved!');
|
|
});
|
|
```
|
|
|
|
This function also supports async/await:
|
|
|
|
```javascript
|
|
(async () => {
|
|
try {
|
|
await writeFileAtomic('message.txt', 'Hello Node', {chown:{uid:100,gid:50}});
|
|
console.log('It\'s saved!');
|
|
} catch (err) {
|
|
console.error(err);
|
|
process.exit(1);
|
|
}
|
|
})();
|
|
```
|
|
|
|
### var writeFileAtomicSync = require('write-file-atomic').sync<br>writeFileAtomicSync(filename, data, [options])
|
|
|
|
The synchronous version of **writeFileAtomic**.
|