The inet_addr( ), inet_lnaof( ), inet_makeaddr( ), inet_netof( ), inet_network( ), and inet_ntoa( ) functions manipulate Internet addresses.

unsigned long inet_addr(cp) 
  char *cp; 

int inet_lnaof(in) 
  struct in_addr in; 

struct in_addr inet_makeaddr(net, host) 
  int net, host; 

int inet_netof(in) 
  struct in_addr in; 

unsigned long inet_network(cp) 
  char *cp; 

char *inet_ntoa(in) 
  struct in_addr in;

Remarks

The functions inet_addr( ) and inet_network( ) convert dot notation character strings to the equivalent Internet address and network number, respectively. The function inet_ntoa( ) performs the reverse operation, converting an Internet address to the equivalent dot notation character string.

The function inet_makeaddr( ) constructs an Internet address from a network number and host address. The functions inet_netof( ) and inet_lnaof( ) return the network and local network portions, respectively, of the Internet number passed as an argument.

All functions correctly handle Class A, B, and C Internet addresses; Internet addresses are returned in network byte order.

The dot notation form of an Internet address consists of one to four numbers separated by dots (periods). Each number can be expressed in decimal, octal (leading 0), or hexadecimal (leading 0x).

• Four-part addresses (a.b.c.d) consist of four 8-bit numbers, each in the range 0-255. The four parts are assigned, in order, to the four bytes in the long Internet address. This is the most commonly used format.
• Three-part addresses(a.b.c): consist of two 8-bit numbers followed by a 16-bit number. The first two parts are assigned in order to the leftmost two bytes of the long Internet address; the third part is placed in the rightmost two bytes. This format is often used for specifying Class B network addresses as 128.net.host.
• Two-part addresses (a.b): consist of a single 8-bit number followed a 24-bit number. The first part is assigned to the leftmost byte of the long Internet address; the second part is placed in the rightmost three bytes. This format is often used for specifying Class A addresses as net.host.
• One-part addresses are converted to a 32-bit quantity and stored directly in the long Internet address without any byte rearrangement.