C++ epoll select poll

C provides several system calls for multiplexing I/O operations, including epoll, select, and poll. These system calls allow a program to monitor multiple file descriptors (e.g. sockets or pipes) for I/O readiness, and block until at least one becomes ready.

1. epoll: epoll is a scalable I/O event notification mechanism introduced in Linux kernel version 2.6. It is considered more efficient than select and poll for large-scale applications. epoll can monitor a large number of file descriptors, and can return only those that are ready for I/O operations.

2. select: select is a system call that allows a program to monitor multiple file descriptors for I/O readiness. It is available on most Unix-like operating systems. select has some limitations, such as a maximum number of file descriptors that can be monitored and the need to iterate over all monitored file descriptors to find the ready ones.

3. poll: poll is another system call that allows a program to monitor multiple file descriptors for I/O readiness. It is similar to select, but with some differences in its interface and behavior. Like select, poll has a maximum number of file descriptors that can be monitored.

In general, epoll is considered the most efficient and scalable option for large-scale applications, while select and poll are suitable for simpler applications with fewer file descriptors. However, the choice of multiplexing mechanism depends on the specific requirements of the application.