Efficiency: epoll is generally more efficient than select because epoll uses a more scalable event notification mechanism and allows for large numbers of file descriptors to be monitored efficiently.
Scalability: epoll is better at handling large numbers of file descriptors compared to select. Epoll is able to scale linearly with the number of file descriptors being monitored, while select has performance issues when monitoring a large number of file descriptors.
Edge-triggered vs Level-triggered: epoll supports both edge-triggered and level-triggered modes, while select only supports level-triggered mode. Edge-triggered mode means that epoll will only notify the application when there is a change in the file descriptor’s status, while level-triggered mode means that epoll will notify the application whenever the file descriptor is ready for reading or writing.
API: epoll has a more complex API compared to select, which can make it more difficult for beginners to use. Select is simpler and easier to use, but it may not be as efficient or scalable as epoll.
Portability: epoll is only available on Linux systems, while select is more widely supported and available on multiple operating systems.
In conclusion, epoll is generally preferred over select for high-performance applications that require efficient monitoring of a large number of file descriptors. However, select may still be a suitable choice for simpler applications or for applications that need to be cross-platform compatible.