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253 lines
6.2 KiB
Groff
253 lines
6.2 KiB
Groff
.\" $NetBSD: nsdispatch.3,v 1.8 1999/03/22 19:44:53 garbled 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. 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 October 15, 2018
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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 sys/types.h
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.In stdarg.h
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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_name"
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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 methods specified in
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.Va dtab
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in the order given by
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.Xr nsswitch.conf 5
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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 method to modify as necessary, to pass back results to
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the caller of
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.Fn nsdispatch .
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.Pp
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Each method has the function signature described by the typedef:
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.Pp
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.Ft typedef int
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.Fn \*(lp*nss_method\*(rp "void *retval" "void *mdata" "va_list *ap" ;
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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 _ns_dtab {
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const char *src;
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nss_method method;
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void *mdata;
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} ns_dtab;
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.Ed
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.Pp
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The
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.Fa dtab
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array should consist of one entry for each source type that is
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implemented, with
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.Va src
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as the name of the source,
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.Va method
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as a function which handles that source, and
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.Va mdata
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as a handle on arbitrary data to be passed to the method.
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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 method ,
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and
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.Va mdata .
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.Pp
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Additionally, methods may be implemented in NSS modules, in
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which case they are selected using the
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.Fa database
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and
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.Fa method_name
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arguments along with the configured source.
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Modules must use source names different from the built-in ones.
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.Pp
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.Va defaults
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contains a list of default sources to try if
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.Xr nsswitch.conf 5
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is missing or corrupted, or if there is no 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 _ns_src {
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const char *src;
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uint32_t flags;
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} ns_src;
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.Ed
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.Pp
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The
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.Fa defaults
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array should consist of one entry for each source to be configured by
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default indicated by
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.Va src ,
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and
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.Va flags
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set to the criterion desired
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(usually
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.Dv NS_SUCCESS ;
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refer to
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.Sx Method 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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.Pp
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.Dl extern const ns_src __nsdefaultsrc[];
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.Pp
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exists which contains a single default entry for the source
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.Sq files
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that may be used by callers which do not require complicated default
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rules.
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.Pp
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.Sq Va ...
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are optional extra arguments, which are passed to the appropriate method
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as a variable argument list of the type
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.Vt va_list .
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.Ss Valid source types
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While there is support for arbitrary sources, the following
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#defines for commonly implemented sources are available:
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.Bl -column NSSRC_COMPAT compat -offset indent
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.It Sy "#define value"
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.It Dv NSSRC_FILES Ta \&"files\&"
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.It Dv NSSRC_DB Ta \&"db\&"
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.It Dv NSSRC_DNS Ta \&"dns\&"
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.It Dv NSSRC_NIS Ta \&"nis\&"
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.It Dv NSSRC_COMPAT Ta \&"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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.Ss Method return values
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The
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.Vt nss_method
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functions must return one of the following values depending upon status
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of the lookup:
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.Bl -column "Return value" "Status code"
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.It Sy "Return value Status code"
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.It Dv NS_SUCCESS Ta success
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.It Dv NS_NOTFOUND Ta notfound
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.It Dv NS_UNAVAIL Ta unavail
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.It Dv NS_TRYAGAIN Ta tryagain
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.It Dv NS_RETURN Ta -none-
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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 each status code.
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.Pp
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The
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.Fn nsdispatch
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function returns the value of the method that caused the dispatcher to
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terminate, or
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.Dv NS_NOTFOUND
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otherwise.
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.Sh NOTES
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.Fx Ns 's
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.Lb libc
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provides stubs for compatibility with NSS modules
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written for the
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.Tn GNU
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C Library
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.Nm nsswitch
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interface.
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However, these stubs only support the use of the
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.Dq Li passwd
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and
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.Dq Li group
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databases.
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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 nsswitch.conf 5 ,
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.Xr yp 8
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.Sh HISTORY
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The
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.Fn nsdispatch
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function first appeared in
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.Fx 5.0 .
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It was imported from the
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.Nx
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Project,
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where it appeared first in
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.Nx 1.4 .
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Support for NSS modules first appeared in
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.Fx 5.1 .
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.Sh AUTHORS
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.An Luke Mewburn Aq Mt 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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svc.conf(5)
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and
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.Tn Solaris
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nsswitch.conf(4)
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manual pages.
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The
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.Fx
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Project
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added the support for threads and NSS modules, and normalized the uses
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of
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.Fn nsdispatch
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within the standard C library.
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