Using FD_ZERO Macro

select FD_ZERO

This C macro is used to initialize a file descriptor set. Before you can register file descriptors (which includes sockets), you must initialize your set to all zero bits. To initialize a file descriptor set named read_socks and write_socks, you would write the following C language statements:

Example

fd_set read_socks;

fd_set write_socks;

FD_ZERO(&read_socks);

FD_ZERO(&write_socks);

The first two statements declare the storage associated with the file descriptor sets. The last two statements, which use the FD_ZERO macro, initialize these sets to the empty set. In other words, after FD_ZERO has been applied on a set, there are no file  descriptors left registered within the set.