REALHOSTNAME(3)        FreeBSD Library Functions Manual        REALHOSTNAME(3)

NAME
     realhostname - convert an IP number to the real host name

LIBRARY
     System Utilities Library (libutil, -lutil)

SYNOPSIS
     #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 ensuring 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 <libutil.h>:

        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 numeric 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), realhostname_sa(3)

HISTORY
     The realhostname() function first appeared in FreeBSD 3.2.

FreeBSD 13.1-RELEASE-p6          April 6, 1999         FreeBSD 13.1-RELEASE-p6