*nix Documentation Project
·  Home
 +   man pages
·  Linux HOWTOs
·  FreeBSD Tips
·  *niX Forums

  man pages->FreeBSD man pages -> recno (3)              



NAME    [Toc]    [Back]

     recno -- record number database access method

SYNOPSIS    [Toc]    [Back]

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

DESCRIPTION    [Toc]    [Back]

     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;
	     u_char bval;
	     char *bfname;

     The elements of this structure are defined as follows:

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

		     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.

		     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 applications to retrieve records at the end
		     of files without reading all of the intervening records.

		     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.

	     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 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 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 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 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 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    [Toc]    [Back]

     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    [Toc]    [Back]

     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    [Toc]    [Back]

     Only big and little endian byte order is supported.

FreeBSD 5.2.1			August 18, 1994 		 FreeBSD 5.2.1
[ Back ]
 Similar pages
Name OS Title
btree Linux btree database access method
hash OpenBSD hash database access method
btree IRIX btree database access method
hash NetBSD hash database access method
hash FreeBSD hash database access method
hash Linux hash database access method
hash Tru64 hash database access method
btree OpenBSD btree database access method
btree FreeBSD btree database access method
btree Tru64 btree database access method
Copyright © 2004-2005 DeniX Solutions SRL
newsletter delivery service