function Deno.umask
umask(mask?: number): number
Retrieve the process umask. If `mask` is provided, sets the process umask.
This call always returns what the umask was before the call.
```ts
console.log(Deno.umask()); // e.g. 18 (0o022)
const prevUmaskValue = Deno.umask(0o077); // e.g. 18 (0o022)
console.log(Deno.umask()); // e.g. 63 (0o077)
```
This API is under consideration to determine if permissions are required to
call it.
*Note*: This API is not implemented on Windows
number