select function file descriptor

select function file descriptor

The second, third, and fourth arguments of the select(2) function call require values of type fd_set, which might be new to you. This is an opaque data type, requiring that it be operated upon with macros provided for the purpose. The following is a synopsis of the macros for your use:

Example

FD_ZERO(fd_set *set);

FD_SET(int fd, fd_set *set);

FD_CLR(int fd, fd_set *set);

FD_ISSET(int fd, fd_set *set);

These C macros allow you to manipulate sets of file descriptors.