Retrieve the process umask. If mask is provided, sets the process umask. This call always returns what the umask was before the call.

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