select,poll,epoll

Select

select() and pselect() allow a program to monitor multiple file descriptors, waiting until one or more of the file descriptors become "ready" for some class of I/O operation (e.g., input possible). A file descriptor is considered ready if it is possible to perform the corresponding I/O operation without blocking.

https://linux.die.net/man/2/select

Poll

http://www.cnblogs.com/alyssaCui/archive/2013/04/01/2993886.html

Epoll

http://www.unixlinux.online/unixlinux/linuxjc/gylinux/201703/72932.html