function Deno.truncate
truncate(name: string,len?: number,): Promise<void>
Truncates (or extends) the specified file, to reach the specified `len`.
If `len` is not specified then the entire file contents are truncated.
### Truncate the entire file
```ts
await Deno.truncate("my_file.txt");
```
### Truncate part of the file
```ts
const file = await Deno.makeTempFile();
await Deno.writeTextFile(file, "Hello World");
await Deno.truncate(file, 7);
const data = await Deno.readFile(file);
console.log(new TextDecoder().decode(data)); // "Hello W"
```
Requires `allow-write` permission.
Promise<void>