What are the different I/O models in Linux and how to use them?

In Linux, there are various IO models available for use, including:

1. Blocking IO: In this model, the application will wait until the IO operation is completed. This means that the application will be blocked on the IO operation and cannot perform other tasks. Standard read() and write() functions can be used for blocking IO operations.
2. Non-blocking IO: In this model, the application can immediately return and continue with other tasks without waiting for the IO operation to complete. You can set the file descriptor to non-blocking mode using the fcntl() function and perform non-blocking IO operations using the read() and write() functions.
3. Multiplexing IO: In this model, the application uses system calls such as select() or epoll() to wait for IO events on multiple file descriptors, and then performs the corresponding IO operations. This allows multiple IO operations to be processed concurrently in a single thread, improving system performance.
4. Signal-driven IO is a model where applications use signals, such as SIGIO signals, to notify the occurrence of IO events. The file descriptor’s owner can be set using the fcntl() function, and the IO events can be handled using signal handler functions.
5. Asynchronous IO: In this model, applications initiate IO operations by calling specific asynchronous IO functions (such as aio_read() and aio_write()), and receive results through callback functions after the IO operations are completed. This enables true asynchronous IO operations.

Choose the appropriate I/O model based on your specific needs and scenarios, and utilize the corresponding system calls or functions to operate.