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(libc.info)Host Address Functions

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Host Address Functions
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These additional functions for manipulating Internet addresses are
declared in the header file `arpa/inet.h'.  They represent Internet
addresses in network byte order, and network numbers and
local-address-within-network numbers in host byte order.  Note: Byte
Order, for an explanation of network and host byte order.

 - Function: int inet_aton (const char *NAME, struct in_addr *ADDR)
     This function converts the IPv4 Internet host address NAME from
     the standard numbers-and-dots notation into binary data and stores
     it in the `struct in_addr' that ADDR points to.  `inet_aton'
     returns nonzero if the address is valid, zero if not.

 - Function: uint32_t inet_addr (const char *NAME)
     This function converts the IPv4 Internet host address NAME from the
     standard numbers-and-dots notation into binary data.  If the input
     is not valid, `inet_addr' returns `INADDR_NONE'.  This is an
     obsolete interface to `inet_aton', described immediately above. It
     is obsolete because `INADDR_NONE' is a valid address
     (255.255.255.255), and `inet_aton' provides a cleaner way to
     indicate error return.

 - Function: uint32_t inet_network (const char *NAME)
     This function extracts the network number from the address NAME,
     given in the standard numbers-and-dots notation. The returned
     address is in host order. If the input is not valid,
     `inet_network' returns `-1'.

     The function works only with traditional IPv4 class A, B and C
     network types.  It doesn't work with classless addresses and
     shouldn't be used anymore.

 - Function: char * inet_ntoa (struct in_addr ADDR)
     This function converts the IPv4 Internet host address ADDR to a
     string in the standard numbers-and-dots notation.  The return
     value is a pointer into a statically-allocated buffer.  Subsequent
     calls will overwrite the same buffer, so you should copy the
     string if you need to save it.

     In multi-threaded programs each thread has an own
     statically-allocated buffer.  But still subsequent calls of
     `inet_ntoa' in the same thread will overwrite the result of the
     last call.

     Instead of `inet_ntoa' the newer function `inet_ntop' which is
     described below should be used since it handles both IPv4 and IPv6
     addresses.

 - Function: struct in_addr inet_makeaddr (uint32_t NET, uint32_t LOCAL)
     This function makes an IPv4 Internet host address by combining the
     network number NET with the local-address-within-network number
     LOCAL.

 - Function: uint32_t inet_lnaof (struct in_addr ADDR)
     This function returns the local-address-within-network part of the
     Internet host address ADDR.

     The function works only with traditional IPv4 class A, B and C
     network types.  It doesn't work with classless addresses and
     shouldn't be used anymore.

 - Function: uint32_t inet_netof (struct in_addr ADDR)
     This function returns the network number part of the Internet host
     address ADDR.

     The function works only with traditional IPv4 class A, B and C
     network types.  It doesn't work with classless addresses and
     shouldn't be used anymore.

 - Function: int inet_pton (int AF, const char *CP, void *BUF)
     This function converts an Internet address (either IPv4 or IPv6)
     from presentation (textual) to network (binary) format.  AF should
     be either `AF_INET' or `AF_INET6', as appropriate for the type of
     address being converted.  CP is a pointer to the input string, and
     BUF is a pointer to a buffer for the result.  It is the caller's
     responsibility to make sure the buffer is large enough.

 - Function: const char * inet_ntop (int AF, const void *CP, char *BUF,
          size_t LEN)
     This function converts an Internet address (either IPv4 or IPv6)
     from network (binary) to presentation (textual) form.  AF should be
     either `AF_INET' or `AF_INET6', as appropriate.  CP is a pointer
     to the address to be converted.  BUF should be a pointer to a
     buffer to hold the result, and LEN is the length of this buffer.
     The return value from the function will be this buffer address.