FreeBSD Manual Pages
INET(3) Library Functions Manual INET(3) NAME inet_aton, inet_addr, inet_network, inet_ntoa, inet_ntoa_r, inet_ntop, inet_pton, inet_makeaddr, inet_lnaof, inet_netof -- Internet address manip- ulation routines LIBRARY Standard C Library (libc, -lc) SYNOPSIS #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> int inet_aton(const char *cp, struct in_addr *pin); in_addr_t inet_addr(const char *cp); in_addr_t inet_network(const char *cp); char * inet_ntoa(struct in_addr in); char * inet_ntoa_r(struct in_addr in, char *buf, socklen_t size); const char * inet_ntop(int af, const void * restrict src, char * restrict dst, socklen_t size); int inet_pton(int af, const char * restrict src, void * restrict dst); struct in_addr inet_makeaddr(in_addr_t net, in_addr_t lna); in_addr_t inet_lnaof(struct in_addr in); in_addr_t inet_netof(struct in_addr in); DESCRIPTION The routines inet_aton(), inet_addr() and inet_network() interpret charac- ter strings representing numbers expressed in the Internet standard `.' no- tation. The inet_pton() function converts a presentation format address (that is, printable form as held in a character string) to network format (usually a struct in_addr or some other internal binary representation, in network byte order). It returns 1 if the address was valid for the specified ad- dress family, or 0 if the address was not parseable in the specified ad- dress family, or -1 if some system error occurred (in which case errno will have been set). This function is presently valid for AF_INET and AF_INET6. The inet_aton() routine interprets the specified character string as an In- ternet address, placing the address into the structure provided. It re- turns 1 if the string was successfully interpreted, or 0 if the string is invalid. The inet_addr() and inet_network() functions return numbers suit- able for use as Internet addresses and Internet network numbers, respec- tively. The function inet_ntop() converts an address *src from network format (usu- ally a struct in_addr or some other binary form, in network byte order) to presentation format (suitable for external display purposes). The size ar- gument specifies the size, in bytes, of the buffer *dst. INET_ADDRSTRLEN and INET6_ADDRSTRLEN define the maximum size required to convert an address of the respective type. It returns NULL if a system error occurs (in which case, errno will have been set), or it returns a pointer to the destination string. This function is presently valid for AF_INET and AF_INET6. The routine inet_ntoa() takes an Internet address and returns an ASCII string representing the address in `.' notation. The routine inet_ntoa_r() is the reentrant version of inet_ntoa(). The deprecated routine inet_makeaddr() takes an Internet network number and a local host address on that network, and constructs an Internet address from it. It should only be assumed to work for historical class A/B/C networks. The depre- cated routines inet_netof() and inet_lnaof() break apart Internet host ad- dresses, returning the network number and local host address part, respec- tively, assuming the historical class A/B/C network masks. 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 byte order integer values. INTERNET ADDRESSES (IP VERSION 4) The inet_aton() and inet_addr() functions accept IPv4 values specified us- ing the `.' notation in 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 least significant two bytes of the net- work address. When a two part address is supplied, the last part is interpreted as a 24-bit quantity and placed in the least significant three bytes of the net- work address. 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 im- plies hexadecimal; otherwise, a leading 0 implies octal; otherwise, the number is interpreted as decimal). Note that inet_pton() does not accept 1-, 2-, or 3-part dotted addresses; all four parts must be specified and are interpreted only as decimal val- ues. This is a narrower input set than that accepted by inet_aton(). DIAGNOSTICS The constant INADDR_NONE is returned by inet_addr() and inet_network() for malformed requests. ERRORS The inet_ntop() call fails if: [ENOSPC] size was not large enough to store the presentation form of the address. [EAFNOSUPPORT] *src was not an AF_INET or AF_INET6 family address. SEE ALSO byteorder(3), getaddrinfo(3), gethostbyname(3), getnameinfo(3), getne- tent(3), inet_net(3), hosts(5), networks(5) IP Version 6 Addressing Architecture, RFC, 2373, July 1998. STANDARDS The inet_ntop() and inet_pton() functions conform to X/Open Networking Ser- vices Issue 5.2 ("XNS5.2"). HISTORY These functions appeared in 4.2BSD. BUGS 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. The inet_addr() function should return a struct in_addr. FreeBSD ports 15.quarterly November 9, 2021 INET(3)
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | INTERNET ADDRESSES (IP VERSION 4) | DIAGNOSTICS | ERRORS | SEE ALSO | STANDARDS | HISTORY | BUGS
Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=inet_aton&sektion=3&manpath=FreeBSD+15.1-RELEASE+and+Ports.quarterly>