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RECNO(3)	       FreeBSD 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 descrip-
     tion 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 num-
     ber.  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;
     } RECNOINFO;

     The elements of this structure are	defined	as follows:

     flags   The flag value is specified by or'ing any of the following	val-
	     ues:

	     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(), 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() is called, instead of permitting any	unmod-
		     ified 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 speci-
	     fied) 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
     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.

FreeBSD	10.1			August 18, 1994			  FreeBSD 10.1

NAME | SYNOPSIS | DESCRIPTION | ERRORS | SEE ALSO | BUGS

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