CURLOPT_SHARE(3) on macOS
The text f4eec3517ee9, as macOS 10.14.6, macOS 10.14.5, macOS 10.14.4, macOS 10.14.3, macOS 10.14.2, macOS 10.14.1, macOS 10.14, macOS 10.13.6, macOS 10.13.5, macOS 10.13.4, macOS 10.13.3, macOS 10.13.2, macOS 10.13.1, macOS 10.13, macOS 10.12.6 shipped it.
specify share handle to use