fs.realpath(path[, options], callback)

    通过解析 ... 和符号链接异步地计算规范路径名。

      Asynchronously computes the canonical pathname by resolving ., .., and symbolic links.

      A canonical pathname is not necessarily unique. Hard links and bind mounts can expose a file system entity through many pathnames.

      This function behaves like realpath(3), with some exceptions:

      1. No case conversion is performed on case-insensitive file systems.

      2. The maximum number of symbolic links is platform-independent and generally (much) higher than what the native realpath(3) implementation supports.

      The callback gets two arguments (err, resolvedPath). May use process.cwd to resolve relative paths.

      Only paths that can be converted to UTF8 strings are supported.

      The optional options argument can be a string specifying an encoding, or an object with an encoding property specifying the character encoding to use for the path passed to the callback. If the encoding is set to 'buffer', the path returned will be passed as a <Buffer> object.

      If path resolves to a socket or a pipe, the function will return a system dependent name for that object.