--- name: "getipnodebyname" section: "3" platform: "linux" package: "man-pages" version: "6.19-1" release: "Arch Linux 2026-11-01" platforms: ["linux", "freebsd", "macos"] url: "https://new.carta.tech/getipnodebyname" --- # getipnodebyname(3) get network hostnames and addresses ## NAME getipnodebyname, getipnodebyaddr, freehostent - get network hostnames and addresses ## LIBRARY Standard C library (*libc*, *-lc*) ## SYNOPSIS ``` #include #include #include ``` **\[\[deprecated\]\] struct hostent \*getipnodebyname(const char \****name***, int** *af***,** **int** *flags***, int \****error\_num***);** **\[\[deprecated\]\] struct hostent \*getipnodebyaddr(**size\_t size; **const void** *addr***\[***size***\],** **size\_t** *size***, int** *af***,** **int \****error\_num***);** **\[\[deprecated\]\] void freehostent(struct hostent \****ip***);** ## DESCRIPTION These functions are deprecated (and unavailable in glibc). Use [**getaddrinfo**(3)](/getaddrinfo/3.md) and [**getnameinfo**(3)](/getnameinfo/3.md) instead. The **getipnodebyname**() and **getipnodebyaddr**() functions return the names and addresses of a network host. These functions return a pointer to the following structure: ``` struct hostent { char *h_name; char **h_aliases; int h_addrtype; int h_length; char **h_addr_list; }; ``` These functions replace the [**gethostbyname**(3)](/gethostbyname/3.md) and [**gethostbyaddr**(3)](/gethostbyaddr/3.md) functions, which could access only the IPv4 network address family. The **getipnodebyname**() and **getipnodebyaddr**() functions can access multiple network address families. Unlike the **gethostby** functions, these functions return pointers to dynamically allocated memory. The **freehostent**() function is used to release the dynamically allocated memory after the caller no longer needs the *hostent* structure. ### getipnodebyname() arguments The **getipnodebyname**() function looks up network addresses for the host specified by the *name* argument. The *af* argument specifies one of the following values: - **AF\_INET** The *name* argument points to a dotted-quad IPv4 address or a name of an IPv4 network host. - **AF\_INET6** The *name* argument points to a hexadecimal IPv6 address or a name of an IPv6 network host. The *flags* argument specifies additional options. More than one option can be specified by bitwise OR-ing them together. *flags* should be set to 0 if no options are desired. - **AI\_V4MAPPED** This flag is used with **AF\_INET6** to request a query for IPv4 addresses instead of IPv6 addresses; the IPv4 addresses will be mapped to IPv6 addresses. - **AI\_ALL** This flag is used with **AI\_V4MAPPED** to request a query for both IPv4 and IPv6 addresses. Any IPv4 address found will be mapped to an IPv6 address. - **AI\_ADDRCONFIG** This flag is used with **AF\_INET6** to further request that queries for IPv6 addresses should not be made unless the system has at least one IPv6 address assigned to a network interface, and that queries for IPv4 addresses should not be made unless the system has at least one IPv4 address assigned to a network interface. This flag may be used by itself or with the **AI\_V4MAPPED** flag. - **AI\_DEFAULT** This flag is equivalent to **(AI\_ADDRCONFIG \| AI\_V4MAPPED)**. ### getipnodebyaddr() arguments The **getipnodebyaddr**() function looks up the name of the host whose network address is specified by the *addr* argument. The *af* argument specifies one of the following values: - **AF\_INET** The *addr* argument points to a *struct in\_addr* and *size* must be set to *sizeof(struct in\_addr)*. - **AF\_INET6** The *addr* argument points to a *struct in6\_addr* and *size* must be set to *sizeof(struct in6\_addr)*. ## RETURN VALUE NULL is returned if an error occurred, and *error\_num* will contain an error code from the following list: - **HOST\_NOT\_FOUND** The hostname or network address was not found. - **NO\_ADDRESS** The domain name server recognized the network address or name, but no answer was returned. This can happen if the network host has only IPv4 addresses and a request has been made for IPv6 information only, or vice versa. - **NO\_RECOVERY** The domain name server returned a permanent failure response. - **TRY\_AGAIN** The domain name server returned a temporary failure response. You might have better luck next time. A successful query returns a pointer to a *hostent* structure that contains the following fields: - *h\_name* This is the official name of this network host. - *h\_aliases* This is an array of pointers to unofficial aliases for the same host. The array is terminated by a null pointer. - *h\_addrtype* This is a copy of the *af* argument to **getipnodebyname**() or **getipnodebyaddr**(). *h\_addrtype* will always be **AF\_INET** if the *af* argument was **AF\_INET**. *h\_addrtype* will always be **AF\_INET6** if the *af* argument was **AF\_INET6**. - *h\_length* This field will be set to *sizeof(struct in\_addr)* if *h\_addrtype* is **AF\_INET**, and to *sizeof(struct in6\_addr)* if *h\_addrtype* is **AF\_INET6**. - *h\_addr\_list* This is an array of one or more pointers to network address structures for the network host. The array is terminated by a null pointer. ## STANDARDS None. ## HISTORY RFC 2553. Present in glibc 2.1.91-95, but removed again. Several UNIX-like systems support them, but all call them deprecated. ## SEE ALSO [**getaddrinfo**(3)](/getaddrinfo/3.md), [**getnameinfo**(3)](/getnameinfo/3.md), [**inet\_ntop**(3)](/inet_ntop/3.md), [**inet\_pton**(3)](/inet_pton/3.md)