realhostname(3)

NAME

realhostname - convert an IP number to the real host name

LIBRARY

System Utilities Library (libutil, -lutil)

SYNOPSIS

#include <sys/types.h>
#include <netinet/in.h>
#include <libutil.h>
int
realhostname(char *host, size_t hsize, const struct  in_addr
*ip);

DESCRIPTION

The function realhostname() converts ip to the corresponding

host name.
This is done by resolving ip to a host name and then ensur

ing that the
host name resolves back to ip.

host must point to a buffer of at least hsize bytes, and

will always be
written to by this function.

If the name resolution does not work both ways or if the

host name is
longer than hsize bytes, inet_ntoa(3) is used to convert ip

to an ASCII
form.

If the string written to host is hsize bytes long, host will

not be NUL
terminated.

RETURN VALUES

The realhostname() function will return one of the following

constants
which are defined in

HOSTNAME_FOUND

A valid host name was found.

HOSTNAME_INCORRECTNAME

A host name was found, but it did not resolve back

to the passed
ip. host now contains the numeric value of ip.

HOSTNAME_INVALIDADDR

ip could not be resolved. host now contains the nu

meric value of
ip.

HOSTNAME_INVALIDNAME

A host name was found, but it could not be resolved

back to any
ip number. host now contains the numeric value of

ip.

SEE ALSO

gethostbyaddr(3), gethostbyname(3), inet_ntoa(3), realhost

name_sa(3)

BSD April 6, 1999

BSD