process.stderr

The process.stderr property returns a stream connected to stderr (fd 2). It is a net.Socket (which is a Duplex stream) unless fd 2 refers to a file, in which case it is a Writable stream.

process.stderr differs from other Node.js streams in important ways. See note on process I/O for more information.

This property refers to the value of underlying file descriptor of process.stderr. The value is fixed at 2. In Worker threads, this field does not exist.