307 lines
6.5 KiB
Groff
307 lines
6.5 KiB
Groff
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.\" $NetBSD: dbm_clearerr.3,v 1.5 2010/05/05 06:55:57 jruoho Exp $
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.\"
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.\" Copyright (c) 2004 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 Klaus Klein.
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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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.\"
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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 May 5, 2010
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.Dt DBM_CLEARERR 3
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.Os
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.Sh NAME
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.Nm dbm_clearerr ,
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.Nm dbm_close ,
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.Nm dbm_delete ,
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.Nm dbm_dirfno ,
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.Nm dbm_error ,
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.Nm dbm_fetch ,
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.Nm dbm_firstkey ,
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.Nm dbm_nextkey ,
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.Nm dbm_open ,
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.Nm dbm_store ,
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.Nm ndbm
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.Nd database functions
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In ndbm.h
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.Ft int
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.Fn dbm_clearerr "DBM *db"
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.Ft void
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.Fn dbm_close "DBM *db"
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.Ft int
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.Fn dbm_delete "DBM *db" "datum key"
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.Ft int
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.Fn dbm_dirfno "DBM *db"
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.Ft int
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.Fn dbm_error "DBM *db"
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.Ft datum
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.Fn dbm_fetch "DBM *db" "datum key"
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.Ft datum
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.Fn dbm_firstkey "DBM *db"
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.Ft datum
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.Fn dbm_nextkey "DBM *db"
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.Ft DBM *
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.Fn dbm_open "const char *file" "int open_flags" "mode_t file_mode"
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.Ft int
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.Fn dbm_store "DBM *db" "datum key" "datum content" "int store_mode"
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.Sh DESCRIPTION
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The
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.Nm ndbm
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facility provides access to hash database files.
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.Pp
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Two data types are fundamental to the
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.Nm ndbm
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facility.
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.Fa DBM
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serves as a handle to a database.
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It is an opaque type.
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.Pp
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The other data type is
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.Fa datum ,
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which is a structure type which includes the following members:
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.Bd -literal -offset indent
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void * dptr
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size_t dsize
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.Ed
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.Pp
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A
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.Fa datum
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is thus given by
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.Fa dptr
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pointing at an object of
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.Fa dsize
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bytes in length.
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.Pp
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The
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.Fn dbm_open
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function opens a database.
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The
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.Fa file
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argument is the pathname which the actual database file pathname
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is based on.
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This implementation uses a single file with the suffix
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.Pa .db
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appended to
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.Fa file .
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The
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.Fa open_flags
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argument has the same meaning as the
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.Fa flags
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argument to
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.Xr open 2
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except that when opening a database for write-only access the file
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is opened for read/write access, and the
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.Dv O_APPEND
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flag must not be specified.
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The
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.Fa file_mode
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argument has the same meaning as the
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.Fa mode
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argument to
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.Xr open 2 .
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.Pp
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For the following functions, the
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.Fa db
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argument is a handle previously returned by a call to
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.Fn dbm_open .
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.Pp
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The
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.Fn dbm_close
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function closes a database.
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.Pp
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The
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.Fn dbm_fetch
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function retrieves a record from the database.
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The
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.Fa key
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argument is a
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.Fa datum
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that identifies the record to be fetched.
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.Pp
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The
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.Fn dbm_store
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function stores a record into the database.
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The
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.Fa key
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argument is a
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.Fa datum
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that identifies the record to be stored.
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The
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.Fa content
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argument is a
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.Fa datum
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that specifies the value of the record to be stored.
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The
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.Fa store_mode
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argument specifies the behavior of
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.Fn dbm_store
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if a record matching
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.Fa key
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is already present in the database,
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.Fa db .
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.Fa store_mode
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must be one of the following:
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.Bl -tag -width DBM_REPLACEXX -offset indent
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.It Dv DBM_INSERT
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If a record matching
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.Fa key
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is already present, it is left unchanged.
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.It Dv DBM_REPLACE
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If a record matching
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.Fa key
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is already present, its value is replaced by
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.Fa content .
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.El
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.Pp
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If no record matching
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.Fa key
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is present, a new record is inserted regardless of
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.Fa store_mode .
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.Pp
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The
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.Fn dbm_delete
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function deletes a record from the database.
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The
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.Fa key
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argument is a
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.Fa datum
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that identifies the record to be deleted.
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.Pp
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The
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.Fn dbm_firstkey
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function returns the first key in the database.
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.Pp
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The
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.Fn dbm_nextkey
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function returns the next key in the database.
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In order to be meaningful, it must be preceded by a call to
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.Fn dbm_firstkey .
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.Pp
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The
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.Fn dbm_error
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function returns the error indicator of the database.
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.Pp
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The
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.Fn dbm_clearerr
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function clears the error indicator of the database.
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.Pp
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The
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.Fn dbm_dirfno
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function returns the file descriptor of the underlying database file.
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.Sh IMPLEMENTATION NOTES
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The
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.Nm ndbm
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facility is implemented on top of the
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.Xr hash 3
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access method of the
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.Xr db 3
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database facility.
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.Sh RETURN VALUES
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The
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.Fn dbm_open
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function returns a pointer to a
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.Fa DBM
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when successful; otherwise a null pointer is returned.
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.Pp
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The
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.Fn dbm_close
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function returns no value.
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.Pp
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The
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.Fn dbm_fetch
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function returns a content
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.Fa datum ;
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if no record matching
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.Fa key
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was found or if an error occured, its
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.Fa dptr
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member is a null pointer.
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.Pp
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The
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.Fn dbm_store
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function returns 0 when then record was successfully inserted;
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it returns 1 when called with
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.Fa store_mode
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being
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.Dv DBM_INSERT
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and a record matching
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.Fa key
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is already present;
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otherwise a negative value is returned.
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.Pp
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The
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.Fn dbm_delete
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function returns 0 when the record was successfully deleted;
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otherwise a negative value is returned.
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.Pp
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The
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.Fn dbm_firstkey
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and
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.Fn dbm_nextkey
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functions return a key
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.Fa datum .
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When the end of the database is reached or if an error occured, its
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.Fa dptr
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member is a null pointer.
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.Pp
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The
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.Fn dbm_error
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function returns 0 if the error indicator is clear;
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if the error indicator is set a non-zero value is returned.
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.Pp
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The
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.Fn dbm_clearerr
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function always returns 0.
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.Pp
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The
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.Fn dbm_dirfno
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function returns the file descriptor of the underlying database file.
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.Sh ERRORS
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No errors are defined.
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.Sh SEE ALSO
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.Xr open 2 ,
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.Xr db 3 ,
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.Xr hash 3
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.Sh STANDARDS
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The
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.Fn dbm_clearerr ,
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.Fn dbm_close ,
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.Fn dbm_delete ,
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.Fn dbm_error ,
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.Fn dbm_fetch ,
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.Fn dbm_firstkey ,
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.Fn dbm_nextkey ,
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.Fn dbm_open ,
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and
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.Fn dbm_store
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functions conform to
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.St -xpg4.2
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and
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.St -susv2 .
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The
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.Fn dbm_dirfno
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function is an extension.
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