Section (3) recno
Name
recno — record number database access method
Synopsis
#include <sys/types.h> #include <db.h>
DESCRIPTION
Note well: This
page documents interfaces provided in glibc up until version
2.1. Since version 2.2, glibc no longer provides these
interfaces. Probably, you are looking for the APIs provided
by the libdb
library
instead.
The routine dbopen(3) is the library interface to database files. One of the supported file formats is record number files. The general description of the database access methods is in dbopen(3), this manual page describes only the recno-specific information.
The record number data structure is either variable or fixed-length records stored in a flat-file format, accessed by the logical record number. The existence of record number five implies the existence of records one through four, and the deletion of record number one causes record number five to be renumbered to record number four, as well as the cursor, if positioned after record number one, to shift down one record.
The recno access-method-specific data structure provided
to dbopen(3) is defined in the
<
db.h
>
include file as follows:
typedef struct { unsigned long flags
;unsigned int cachesize
;unsigned int psize
;int lorder
;size_t reclen
;unsigned char bval
;char * bfname
;} RECNOINFO;
The elements of this structure are defined as follows:
flags
-
The flag value is specified by ORing any of the following values:
R_FIXEDLEN
-
The records are fixed-length, not byte delimited. The structure element
reclen
specifies the length of the record, and the structure elementbval
is used as the pad character. Any records, inserted into the database, that are less thanreclen
bytes long are automatically padded. R_NOKEY
-
In the interface specified by dbopen(3), the sequential record retrieval fills in both the caller_zsingle_quotesz_s key and data structures. If the
R_NOKEY
flag is specified, the cursor routines are not required to fill in the key structure. This permits applications to retrieve records at the end of files without reading all of the intervening records. R_SNAPSHOT
-
This flag requires that a snapshot of the file be taken when dbopen(3) is called, instead of permitting any unmodified records to be read from the original file.
cachesize
-
A suggested maximum size, in bytes, of the memory cache. This value is only advisory, and the access method will allocate more memory rather than fail. If
cachesize
is 0 (no size is specified), a default cache is used. psize
-
The recno access method stores the in-memory copies of its records in a btree. This value is the size (in bytes) of the pages used for nodes in that tree. If
psize
is 0 (no page size is specified), a page size is chosen based on the underlying filesystem I/O block size. See btree(3) for more information. lorder
-
The byte order for integers in the stored database metadata. The number should represent the order as an integer; for example, big endian order would be the number 4,321. If
lorder
is 0 (no order is specified), the current host order is used. reclen
-
The length of a fixed-length record.
bval
-
The delimiting byte to be used to mark the end of a record for variable-length records, and the pad character for fixed-length records. If no value is specified, newlines ( ) are used to mark the end of variable-length records and fixed-length records are padded with spaces.
bfname
-
The recno access method stores the in-memory copies of its records in a btree. If
bfname
is non-NULL, it specifies the name of the btree file, as if specified as the filename for a dbopen(3) of a btree file.
The data part of the key/data pair used by the
recno
access method is the same
as other access methods. The key is different. The
data
field of the key should be
a pointer to a memory location of type recno_t, as defined in the <
db.h
>
include file. This type is normally the largest unsigned
integral type available to the implementation. The
size
field of the key should be
the size of that type.
Because there can be no metadata associated with the underlying recno access method files, any changes made to the default values (e.g., fixed record length or byte separator value) must be explicitly specified each time the file is opened.
In the interface specified by dbopen(3), using the
put
interface to create a new
record will cause the creation of multiple, empty records if
the record number is more than one greater than the largest
record currently in the database.
ERRORS
The recno
access method
routines may fail and set errno
for any of the errors specified for the library routine
dbopen(3) or the
following:
- EINVAL
-
An attempt was made to add a record to a fixed-length database that was too large to fit.
SEE ALSO
btree(3), dbopen(3), hash(3), mpool(3)
Document Processing in a Relational Database System, Michael Stonebraker, Heidi Stettner, Joseph Kalash, Antonin Guttman, Nadene Lynn, Memorandum No. UCB/ERL M82/32, May 1982.
COLOPHON
This page is part of release 4.16 of the Linux man-pages
project. A
description of the project, information about reporting bugs,
and the latest version of this page, can be found at
https://www.kernel.org/doc/man−pages/.
Copyright (c) 1990, 1993 The Regents of the University of California. All rights reserved. %%%LICENSE_START(BSD_4_CLAUSE_UCB) Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. 3. All advertising materials mentioning features or use of this software must display the following acknowledgement: This product includes software developed by the University of California, Berkeley and its contributors. 4. Neither the name of the University nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS_zsingle_quotesz__zsingle_quotesz_ AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. %%%LICENSE_END (#)recno.3 8.5 (Berkeley) 8/18/94 |