inet_aton, inet_addr, inet_network, inet_isaddr, inet_ntoa,
inet_makeaddr, inet_lnaof, inet_netof - Internet address manipulation
int inet_aton(const char *cp, struct in_addr *pin);
unsigned long inet_addr(const char *cp);
unsigned long inet_network(const char *cp);
int inet_isaddr(const char *cp, uint32_t *addr);
char *inet_ntoa(struct in_addr in);
struct in_addr inet_makeaddr(int net, int lna);
unsigned long inet_lnaof(struct in_addr in);
unsigned long inet_netof(struct in_addr in);
The routines inet_aton, inet_addr and inet_network interpret character
strings representing numbers expressed in the Internet standard "." (dot)
notation. The inet_aton routine interprets the specified character
string as an Internet address, placing the address into 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. To determine if an ASCII string is a
valid representation of an IPv4 address, the function inet_isaddr may be
used. It takes a pointer to the string, cp, and returns a 1 if the
address is valid, 0 otherwise. Additionally, if the addr parameter is
non-NULL, the converted address will be stored at the address pointed to
by addr. The routine inet_ntoa takes an Internet address and returns an
ASCII string representing the address in "." notation. The routine
inet_makeaddr takes an Internet network number and a local network
address and constructs an Internet address from it. The routines
inet_netof and inet_lnaof 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.
Values specified using the "." notation take one of the following forms:
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 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 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 a "." notation may be decimal, octal,
or hexadecimal, as specified in the C language (i.e., a leading 0x or 0X
implies hexadecimal; otherwise, a leading 0 implies octal; otherwise, the
number is interpreted as decimal).
The constant INADDR_NONE is returned by inet_addr and inet_network for
gethostbyname(3N), getnetent(3N), hosts(4), networks(4)
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 string returned by inet_ntoa resides in a static memory area. Thus
printf("%s %s0, inet_ntoa(addr1), inet_ntoa(addr2));
will print the same address twice.
Inet_addr should return a struct in_addr.
The problem of host byte ordering versus network byte ordering is
A simple way to specify Class C network addresses in a manner similar to
that for Class B and Class A is needed.
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