endhostent, gethostbyaddr, gethostbyname, gethostent, sethostent - net‐
work host database functions
cc [ flag ... ] file ... -lxnet [ library ... ]
extern int h_errno;
struct hostent *gethostbyaddr(const void *addr, socklen_t len, int type);
struct hostent *gethostbyname(const char *name);
struct hostent *gethostent(void)
void sethostent(int stayopen);
The gethostent(), gethostbyaddr(), and gethostbyname() functions each
return a pointer to a hostent structure, the members of which contain
the fields of an entry in the network host database.
The gethostent() function reads the next entry of the database, opening
a connection to the database if necessary.
The gethostbyaddr() function searches the database and finds an entry
which matches the address family specified by the type argument and
which matches the address pointed to by the addr argument, opening a
connection to the database if necessary. The addr argument is a
pointer to the binary-format (that is, not null-terminated) address in
network byte order, whose length is specified by the len argument. The
datatype of the address depends on the address family. For an address
of type AF_INET, this is an in_addr structure, defined in
<netinet/in.h>. For an address of type AF_INET6, there is an in6_addr
structure defined in <netinet/in.h>.
The gethostbyname() function searches the database and finds an entry
which matches the host name specified by the name argument, opening a
connection to the database if necessary. If name is an alias for a
valid host name, the function returns information about the host name
to which the alias refers, and name is included in the list of aliases
The sethostent() function opens a connection to the network host data‐
base, and sets the position of the next entry to the first entry. If
the stayopen argument is non-zero, the connection to the host database
will not be closed after each call to gethostent() (either directly, or
indirectly through one of the other gethost*() functions).
The endhostent() function closes the connection to the database.
The gethostent(), gethostbyaddr(), and gethostbyname() functions may
return pointers to static data, which may be overwritten by subsequent
calls to any of these functions.
These functions are generally used with the Internet address family.
On successful completion, gethostbyaddr(), gethostbyname() and gethos‐
tent() return a pointer to a hostent structure if the requested entry
was found, and a null pointer if the end of the database was reached or
the requested entry was not found. Otherwise, a null pointer is
On unsuccessful completion, gethostbyaddr() and gethostbyname() func‐
tions set h_errno to indicate the error.
No errors are defined for endhostent(), gethostent() and sethostent().
The gethostbyaddr() and gethostbyname() functions will fail in the fol‐
lowing cases, setting h_errno to the value shown in the list below.
Any changes to errno are unspecified.
No such host is known.
The server recognised the request and the name but no
address is available. Another type of request to the
name server for the domain might return an answer.
An unexpected server failure occurred which can not
A temporary and possibly transient error occurred,
such as a failure of a server to respond.
See attributes(5) for descriptions of the following attributes:
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
│Interface Stability │ Standard │
│MT-Level │ MT-Safe │
SEE ALSOendservent(3XNET), htonl(3XNET), inet_addr(3XNET), attributes(5), stan‐
Nov 1, 2003 ENDHOSTENT(3XNET)