40 lines
1.3 KiB
Markdown
40 lines
1.3 KiB
Markdown
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# About `fs.read()` & `fs.write()`
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[`fs.read()`](https://nodejs.org/api/fs.html#fs_fs_read_fd_buffer_offset_length_position_callback) & [`fs.write()`](https://nodejs.org/api/fs.html#fs_fs_write_fd_buffer_offset_length_position_callback) are different from other `fs` methods in that their callbacks are called with 3 arguments instead of the usual 2 arguments.
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If you're using them with callbacks, they will behave as usual. However, their promise usage is a little different. `fs-extra` promisifies these methods like [`util.promisify()`](https://nodejs.org/api/util.html#util_util_promisify_original) (only available in Node 8+) does.
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Here's the example promise usage:
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## `fs.read()`
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```js
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// With Promises:
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fs.read(fd, buffer, offset, length, position)
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.then(results => {
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console.log(results)
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// { bytesRead: 20, buffer: <Buffer 0f 34 5d ...> }
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})
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// With async/await:
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async function example () {
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const { bytesRead, buffer } = await fs.read(fd, Buffer.alloc(length), offset, length, position)
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}
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```
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## `fs.write()`
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```js
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// With Promises:
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fs.write(fd, buffer, offset, length, position)
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.then(results => {
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console.log(results)
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// { bytesWritten: 20, buffer: <Buffer 0f 34 5d ...> }
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})
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// With async/await:
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async function example () {
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const { bytesWritten, buffer } = await fs.write(fd, Buffer.alloc(length), offset, length, position)
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}
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```
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