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55 lines
1.3 KiB
Plaintext
55 lines
1.3 KiB
Plaintext
---
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title: Write a file incrementally
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sidebarTitle: Incremental write
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mode: center
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---
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Bun provides an API for incrementally writing to a file. This is useful for writing large files, or for writing to a file over a long period of time.
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Call `.writer()` on a `BunFile` to retrieve a `FileSink` instance. This instance can be used to efficiently buffer data and periodically "flush" it to disk. You can write & flush many times.
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```ts
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const file = Bun.file("/path/to/file.txt");
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const writer = file.writer();
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writer.write("lorem");
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writer.write("ipsum");
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writer.write("dolor");
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writer.flush();
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// continue writing & flushing
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```
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---
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The `.write()` method can accept strings or binary data.
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```ts
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w.write("hello");
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w.write(Buffer.from("there"));
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w.write(new Uint8Array([0, 255, 128]));
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writer.flush();
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```
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---
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The `FileSink` will also auto-flush when its internal buffer is full. You can configure the buffer size with the `highWaterMark` option.
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```ts
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const file = Bun.file("/path/to/file.txt");
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const writer = file.writer({ highWaterMark: 1024 * 1024 }); // 1MB
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```
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---
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When you're done writing to the file, call `.end()` to auto-flush the buffer and close the file.
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```ts
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writer.end();
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```
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---
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Full documentation: [FileSink](https://bun.com/docs/api/file-io#incremental-writing-with-filesink).
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