Getting notifications of data on a file descriptor

You can use either of two simple mechanisms to receive notifications that data is available on a file descriptor:

• You can issue a blocking read() either by opening the object with the ?wait option on the open() call or by clearing the O_NONBLOCK flag using the fcntl() function after the open() call.
• You can use the QNX io_notify() mechanisms to receive a user-specified event; you can also use the select() function, which uses io_notify() under the covers.