inet_aton(3STDC)

NAME | SYNOPSIS | DESCRIPTION | INTERNET ADDRESSES | DIAGNOSTICS | RESTRICTIONS | ATTRIBUTES

NAME

inet, inet_aton, inet_addr, inet_network, inet_ntoa, inet_makeaddr, inet_lnaof, inet_netof- Internet address manipulation routines

SYNOPSIS

#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

int inet_aton(const char * cp, struct in_addr * pin);
unsigned longinet_addr(const char * cp);
unsigned longinet_network(const char * cp);
char *inet_ntoa(struct in_addr in);
struct in_addrinet_makeaddr(u_long net, u_long lna);
unsigned longinet_lnaof(struct in_addr in);
unsigned longinet_netof(struct in_addr in);

DESCRIPTION

The inet_aton , inet_addr and inet_network routines interpret character strings representing numbers expressed in the Internet standard notation. The inet_aton routine interprets the specified character string as an Internet address, placing the address in the structure provided. It returns 1 if the string was successfully interpreted, or 0 if the string is invalid. The inet_addr and inet_network functions return numbers suitable for use as Internet addresses and Internet network numbers, respectively. The inet_ntoa routine takes an Internet address and returns an ASCII string representing the address in Internet notation. The inet_makeaddr routine takes an Internet network number and a local network address and constructs an Internet address from it. The inet_netof and inet_lnaof routines break apart Internet host addresses, returning the network number and local network address part, respectively.

All Internet addresses are returned in network order (bytes ordered from left to right). All network numbers and local address parts are returned as machine format integer values.

INTERNET ADDRESSES

Values specified using the Internet notation take one of the following forms:

---

a.b.c.d
a.b.c
a.b
a

---

When four parts are specified, each is interpreted as a byte of data and assigned, from left to right, to the four bytes of an Internet address.

When a three part address is specified, the last part is interpreted as a 16-bit quantity and placed in the right-most two bytes of the network address. This makes the three part address format convenient for specifying Class B network addresses such as: 128.net.host .

When a two part address is supplied, the last part is interpreted as a 24-bit quantity and placed in the right--most three bytes of the network address. This makes the two part address format convenient for specifying Class A network addresses such as: net.host .

When only one part is given, the value is stored directly in the network address without any byte rearrangement.

All numbers supplied as parts in Internet notation may be decimal, octal, or hexadecimal, as specified in the C language (a leading 0x or 0X implies hexadecimal; a leading 0 implies octal; otherwise, the number is interpreted as decimal).

DIAGNOSTICS

The constant INADDR_NONE is returned by inet_addr and inet_network for malformed requests.

RESTRICTIONS

The value INADDR_NONE (0xffffffff) is a valid broadcast address, but inet_addr cannot return that value without indicating failure. The newer inet_aton function does not share this problem. The problem of host byte ordering versus network byte ordering is confusing. The string returned by inet_ntoa resides in a static memory area, which means that this routine is not reentrant.

inet_addr should return a struct in_addr.

ATTRIBUTES

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPE	ATTRIBUTE VALUE
Interface Stability	Evolving

NAME | SYNOPSIS | DESCRIPTION | INTERNET ADDRESSES | DIAGNOSTICS | RESTRICTIONS | ATTRIBUTES