.TH NETNUM 3 .SH NAME netnum \- compute the network portion of a given Internet (IP) address .SH SYNOPSIS .B #include <network.h> .PP .B int netnum(netpart, address) .br .B IPaddr netpart; .br .B IPaddr address; .br .SH DESCRIPTION .I Netnum extracts the network portion of the Internet address specified by argument \f2address\f1, and places the result in argument \f2netpart\f1. It operates by using the IP class of argument \f2address\f1 to determine whether the network part of the address occupies 1, 2, or 3 bytes, and it zeros the remaining bytes. \f2Netnum\f1 always returns OK. .SH "SEE ALSO" getaddr(2), getnet(2) .SH BUGS .I Netnum does not understand subnets or subnet masks.