INET

Section: C Library Functions (3)
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BSD mandoc
BSD 4.2

NAME

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

SYNOPSIS

Fd #include <sys/socket.h> Fd #include <netinet/in.h> Fd #include <arpa/inet.h> Ft int Fn inet_aton const char *cp struct in_addr *pin Ft unsigned long Fn inet_addr const char *cp Ft unsigned long Fn inet_network const char *cp Ft char * Fn inet_ntoa struct in_addr in Ft struct in_addr Fn inet_makeaddr int net int lna Ft unsigned long Fn inet_lnaof struct in_addr in Ft unsigned long Fn inet_netof struct in_addr in

DESCRIPTION

The routines Fn inet_aton , Fn inet_addr and Fn inet_network interpret character strings representing numbers expressed in the Internet standard `.' notation. The Fn 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 Fn inet_addr and Fn inet_network functions return numbers suitable for use as Internet addresses and Internet network numbers, respectively. The routine Fn inet_ntoa takes an Internet address and returns an ASCII string representing the address in `.' notation. The routine Fn inet_makeaddr takes an Internet network number and a local network address and constructs an Internet address from it. The routines Fn inet_netof and Fn 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.

INTERNET ADDRESSES

Values specified using the `.' 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. Note that when an Internet address is viewed as a 32-bit integer quantity on the VAX the bytes referred to above appear as ``d.c.b.a '' That is, VAX bytes are ordered from right to left.

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).

DIAGNOSTICS

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

HISTORY

These functions appeared in BSD 4.2

BUGS

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

Inet_addr should return a Fa struct in_addr .

This document was created by man2html, using the manual pages.
Time: 19:42:00 GMT, December 25, 2022