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Asio includes classes added to permit synchronous and asynchronous read and write operations to be performed on POSIX file descriptors, such as pipes, standard input and output, and various devices.
          These classes also provide limited support for regular files. This support
          assumes that the underlying read and write operations provided by the operating
          system never fail with EAGAIN
          or EWOULDBLOCK. (This assumption
          normally holds for buffered file I/O.) Synchronous and asynchronous read
          and write operations on file descriptors will succeed but the I/O will
          always be performed immediately. Wait operations, and operations involving
          asio::null_buffers, are not portably supported.
        
For example, to perform read and write operations on standard input and output, the following objects may be created:
posix::stream_descriptor in(my_io_context, ::dup(STDIN_FILENO)); posix::stream_descriptor out(my_io_context, ::dup(STDOUT_FILENO));
These are then used as synchronous or asynchronous read and write streams. This means the objects can be used with any of the read(), async_read(), write(), async_write(), read_until() or async_read_until() free functions.
posix::stream_descriptor, Chat example (C++11).
          POSIX stream descriptors are only available at compile time if supported
          by the target operating system. A program may test for the macro ASIO_HAS_POSIX_STREAM_DESCRIPTOR to determine
          whether they are supported.