232 lines
6.2 KiB
Groff
232 lines
6.2 KiB
Groff
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.\" $NetBSD: nsdispatch.3,v 1.8 1999/03/22 19:44:53 garbled Exp $
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.\" $FreeBSD: src/lib/libc/net/nsdispatch.3,v 1.5 2001/10/01 16:08:56 ru Exp $
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.\"
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.\" Copyright (c) 1997, 1998, 1999 The NetBSD Foundation, Inc.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to The NetBSD Foundation
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.\" by Luke Mewburn.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the NetBSD
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.\" Foundation, Inc. and its contributors.
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.\" 4. Neither the name of The NetBSD Foundation nor the names of its
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.\" contributors may be used to endorse or promote products derived
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.\" from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd January 19, 1999
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.Dt NSDISPATCH 3
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.Os
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.Sh NAME
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.Nm nsdispatch
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.Nd name-service switch dispatcher routine
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In nsswitch.h
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.Ft int
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.Fo nsdispatch
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.Fa "void *retval"
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.Fa "const ns_dtab dtab[]"
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.Fa "const char *database"
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.Fa "const char *method"
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.Fa "const ns_src defaults[]"
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.Fa "..."
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.Fc
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.Sh DESCRIPTION
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The
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.Fn nsdispatch
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function invokes the callback functions specified in
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.Va dtab
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in the order given in
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.Pa /etc/nsswitch.conf
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for the database
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.Va database
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until a successful entry is found.
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.Pp
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.Va retval
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is passed to each callback function to modify as necessary
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(to pass back to the caller of
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.Fn nsdispatch )
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.Pp
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.Va dtab
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is an array of
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.Va ns_dtab
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structures, which have the following format:
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.Bd -literal -offset indent
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typedef struct {
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const char *src;
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int (*cb)(void *retval, void *cb_data, va_list ap);
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void *cb_data;
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} ns_dtab;
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.Ed
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.Pp
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.Bd -ragged -offset indent
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For each source type that is implemented, an entry with
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.Va src
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set to the name of the source,
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.Va cb
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defined as a function which handles that source, and
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.Va cb_data
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is used to pass arbritrary data to the callback function.
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The last entry in
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.Va dtab
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should contain
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.Dv NULL
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values for
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.Va src ,
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.Va cb ,
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and
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.Va cb_data .
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.Ed
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.Pp
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.Va method
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is usually the name of the function calling
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.Fn nsdispatch .
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When dynamic loading is supported, a symbol constructed from
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.Va database ,
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the current source, and
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.Va method
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will be used as the name to invoke the dynamically loaded function.
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.Pp
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.Va defaults
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contains a list of default sources to try in the case of
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a missing or corrupt
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.Xr nsswitch.conf 5 ,
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or if there isn't a relevant entry for
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.Va database .
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It is an array of
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.Va ns_src
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structures, which have the following format:
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.Bd -literal -offset indent
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typedef struct {
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const char *src;
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u_int32_t flags;
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} ns_src;
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.Ed
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.Pp
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.Bd -ragged -offset indent
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For each default source type, an entry with
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.Va src
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set to the name of the source, and
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.Va flags
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set to the relevant flags
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(usually
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.Dv NS_SUCCESS ;
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refer to
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.Sx Callback return values
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for more information).
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The last entry in
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.Va defaults
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should have
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.Va src
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set to
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.Dv NULL
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and
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.Va flags
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set to 0.
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.Pp
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For convenience, a global variable defined as:
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.Dl extern const ns_src __nsdefaultsrc[];
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exists which contains a single default entry for
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.Sq files
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for use by callers which don't require complicated default rules.
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.Ed
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.Pp
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.Sq Va ...
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are optional extra arguments, which
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are passed to the appropriate callback function as a variable argument
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list of the type
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.Va va_list .
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.Ss Valid source types
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Whilst there is support for arbitrary sources, the following
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#defines for commonly implementated sources are available:
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.Bl -column NS_COMPAT COMPAT -offset indent
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.It Sy "#define value"
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.It "NSSRC_FILES ""files"""
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.It "NSSRC_DNS ""dns"""
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.It "NSSRC_NIS ""nis"""
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.It "NSSRC_COMPAT ""compat"""
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.El
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.Pp
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Refer to
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.Xr nsswitch.conf 5
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for a complete description of what each source type is.
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.Pp
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.Ss Callback return values
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The callback functions should return one of the following values
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depending upon status of the lookup:
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.Bl -column NS_NOTFOUND -offset indent
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.It Sy "Return value Status code"
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.It "NS_SUCCESS success"
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.It "NS_NOTFOUND notfound"
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.It "NS_UNAVAIL unavail"
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.It "NS_TRYAGAIN tryagain"
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.El
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.Pp
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Refer to
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.Xr nsswitch.conf 5
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for a complete description of what each status code is.
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.Pp
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.Nm
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returns the value of the callback that caused the dispatcher to finish,
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or NS_NOTFOUND otherwise.
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.Sh SEE ALSO
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.Xr hesiod 3 ,
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.Xr stdarg 3 ,
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.Xr ypclnt 3 ,
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.Xr nsswitch.conf 5
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.Sh HISTORY
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The
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.Nm
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routines first appeared in
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.Fx 4.1 .
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They were imported from the
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.Nx
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Project,
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where they appeared first in
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.Nx 1.4 .
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.Sh AUTHORS
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Luke Mewburn
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.Aq lukem@netbsd.org
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wrote this freely distributable name-service switch implementation,
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using ideas from the
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.Tn ULTRIX
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.Xr svc.conf 5
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and
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.Tn Solaris
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.Xr nsswitch.conf 4
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manual pages.
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.Sh BUGS
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The
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.Nm
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routines are not thread safe.
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This will be rectified in the future.
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.Pp
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Currently there is no support for dynamically loadable dispatcher callback
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functions.
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It is anticipated that this will be added in the future in the back-end
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without requiring changes to code that invokes
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.Fn nsdispatch .
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