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NetBSD 6.1.5 - man page for recno (netbsd section 3)

RECNO(3)			   BSD Library Functions Manual 			 RECNO(3)

NAME
     recno -- record number database access method

SYNOPSIS
     #include <sys/types.h>
     #include <db.h>

DESCRIPTION
     The routine dbopen() 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() is defined in the
     <db.h> include file as follows:

     typedef struct {
	     u_long flags;
	     u_int cachesize;
	     u_int psize;
	     int lorder;
	     size_t reclen;
	     uint8_t bval;
	     char *bfname;
     } RECNOINFO;

     The elements of this structure are defined as follows:

     flags	 The flag value is specified by or'ing any of the following values:

		       R_FIXEDLEN   The records are fixed-length, not byte delimited.  The struc-
				    ture 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(), 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 applica-
				    tions 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() 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 under-
		 lying file system 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 speci-
		 fied, 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 file name for a dbopen() 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 nor-
     mally 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 meta-data 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(), 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)

     Michael Stonebraker, Heidi Stettner, Joseph Kalash, Antonin Guttman, and Nadene Lynn,
     "Document Processing in a Relational Database System", Memorandum No. UCB/ERL M82/32, May
     1982.

BUGS
     Only big and little endian byte order is supported.

BSD					  April 17, 2003				      BSD


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