recno(3)
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 element bval is used as the pad character. Any records, inserted into the database, that are less than reclen bytes long are automatically padded. R_NOKEY In the interface specified by dbopen(3), the sequential record retrieval fills in both the caller'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 ("\n") 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.
BUGS
Only big and little endian byte order is supported.
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 4.09 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/.
Opportunity
Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.
Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.
Free Software
Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.
Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.
Free Books
The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.
Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.
Education
Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.
Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.
