Select (Unix)

select is a system call for polling multiple file descriptors. In C programming, it is declared in the header file sys/select.h or unistd.h. Those files and sys/time.h must be included to use select.

int select(int nfds, fd_set* readfds, fd_set* writefds, fd_set* errorfds, struct timeval* timeout);

To manipulate the fd_set type arguments, the four FD_SET(), FD_CLR(), FD_ZERO() and FD_ISSET() macros can be used.

The function returns the total number of bits set in "readfds", "writefds" and "errorfds", the value of zero if the timeout expired and -1 on error.

External references

* [http://www.cl.cam.ac.uk/cgi-bin/manpage?2+select Unix Manual Page for select]