process.umask()
稳定性: 0 - 弃用. 不带参数调用 process.umask() 会导致进程范围的 umask 被写入两次。 这会在线程之间引入竞争条件，并且是一个潜在的安全漏洞。 没有安全的、跨平台的替代 API。
process.umask() 返回 Node.js 进程的文件模式创建掩码。
子进程从父进程继承掩码。
Stability: 0 - Deprecated. Calling
process.umask() with no argument causes
the process-wide umask to be written twice. This introduces a race condition
between threads, and is a potential security vulnerability. There is no safe,
cross-platform alternative API.process.umask() returns the Node.js process's file mode creation mask. Child
processes inherit the mask from the parent process.