#### posix::basic_descriptor::bytes_readable

Inherited from posix::descriptor_base.

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.

###### Example

    asio::posix::stream_descriptor descriptor(io_service);
    ...
    asio::descriptor_base::bytes_readable command(true);
    descriptor.io_control(command);
    std::size_t bytes_readable = command.get();