IO control command to get the amount of data that can be read without blocking.
typedef implementation_defined bytes_readable;
Implements the FIONREAD IO control command.
asio::posix::stream_descriptor descriptor(io_context); ... asio::descriptor_base::bytes_readable command(true); descriptor.io_control(command); std::size_t bytes_readable = command.get();
Header: asio/posix/descriptor_base.hpp
Convenience header: asio.hpp