.\"	$NetBSD: hesiod.3,v 1.7 2009/03/10 23:36:10 joerg Exp $
.\"
.\" from: #Id: hesiod.3,v 1.9.2.1 1997/01/03 21:02:23 ghudson Exp #
.\"
.\" Copyright 1988, 1996 by the Massachusetts Institute of Technology.
.\"
.\" Permission to use, copy, modify, and distribute this
.\" software and its documentation for any purpose and without
.\" fee is hereby granted, provided that the above copyright
.\" notice appear in all copies and that both that copyright
.\" notice and this permission notice appear in supporting
.\" documentation, and that the name of M.I.T. not be used in
.\" advertising or publicity pertaining to distribution of the
.\" software without specific, written prior permission.
.\" M.I.T. makes no representations about the suitability of
.\" this software for any purpose.  It is provided "as is"
.\" without express or implied warranty.
.\"
.Dd September 16, 2001
.Dt HESIOD 3
.Os
.Sh NAME
.Nm hesiod ,
.Nm hesiod_init ,
.Nm hesiod_resolve ,
.Nm hesiod_free_list ,
.Nm hesiod_to_bind ,
.Nm hesiod_end
.Nd Hesiod name server interface library
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In hesiod.h
.Ft int
.Fn hesiod_init "void **context"
.Ft char
.Fn **hesiod_resolve "void *context" "const char *name" "const char *type"
.Ft void
.Fn hesiod_free_list "void *context" "char **list"
.Ft char
.Fn *hesiod_to_bind "void *context" "const char *name" "const char *type"
.Ft void
.Fn hesiod_end "void *context"
.Sh DESCRIPTION
This family of functions allows you to perform lookups of Hesiod
information, which is stored as text records in the Domain Name
Service.  To perform lookups, you must first initialize a
.Fa context ,
an opaque object which stores information used internally by the
library between calls.
.Fn hesiod_init
initializes a context, storing a pointer to the context in the
location pointed to by the
.Fa context
argument.
.Fn hesiod_end
frees the resources used by a context.
.Pp
.Fn hesiod_resolve
is the primary interface to the library.  If successful, it returns a
list of one or more strings giving the records matching
.Fa name
and
.Fa type .
The last element of the list is followed by a
.Dv NULL
pointer.  It is the caller's responsibility to call
.Fn hesiod_free_list
to free the resources used by the returned list.
.Pp
.Fn hesiod_to_bind
converts
.Fa name
and
.Fa type
into the DNS name used by
.Fn hesiod_resolve .
It is the caller's responsibility to free the returned string using
.Xr free 3 .
.Sh RETURN VALUES
If successful,
.Fn hesiod_init
returns 0; otherwise it returns \-1 and sets
.Va errno
to indicate the error.  On failure,
.Fn hesiod_resolve
and
.Fn hesiod_to_bind
return
.Dv NULL
and set the global variable
.Va errno
to indicate the error.
.Sh ENVIRONMENT
If the environment variable
.Ev HES_DOMAIN
is set, it will override the domain in the Hesiod configuration file.
If the environment variable
.Ev HESIOD_CONFIG
is set, it specifies the location of the Hesiod configuration file.
.Sh ERRORS
Hesiod calls may fail because of:
.Bl -tag -width ECONNREFUSED -compact
.It Er ENOMEM
Insufficient memory was available to carry out the requested operation.
.It Er ENOEXEC
.Fn hesiod_init
failed because the Hesiod configuration file was invalid.
.It Er ECONNREFUSED
.Fn hesiod_resolve
failed because no name server could be contacted to answer the query.
.It Er EMSGSIZE
.Fn hesiod_resolve
or
.Fn hesiod_to_bind
failed because the query or response was too big to fit into the
packet buffers.
.It Er ENOENT
.Fn hesiod_resolve
failed because the name server had no text records matching
.Fa name
and
.Fa type ,
or
.Fn hesiod_to_bind
failed because the
.Fa name
argument had a domain extension which could not be resolved with type
.Dq rhs-extension
in the local Hesiod domain.
.El
.Sh SEE ALSO
.Xr hesiod.conf 5 ,
.Xr named 8
.Rs
.%T Hesiod - Project Athena Technical Plan -- Name Service
.Re
.Sh AUTHORS
.An Steve Dyer, IBM/Project Athena
.An Greg Hudson, MIT Team Athena
.Pp
Copyright 1987, 1988, 1995, 1996 by the Massachusetts Institute of Technology.
.Sh BUGS
The strings corresponding to the
.Ev errno
values set by the Hesiod functions are not particularly indicative of
what went wrong, especially for
.Er ENOEXEC
and
.Er ENOENT .