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RECNO(3)			    Linux Programmer's Manual				 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 meth-
       ods 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  cur-
       sor, 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 struc-
		     ture.  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 advi-
	      sory, and the access method will allocate more memory rather than fail.  If  cache-
	      size 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 underly-
	      ing 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 num-
	      ber 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 th <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 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 3.55 of the Linux man-pages project.  A  description  of  the
       project,     and    information	  about    reporting	bugs,	 can	be    found    at
       http://www.kernel.org/doc/man-pages/.

4.4 Berkeley Distribution		    2012-04-23					 RECNO(3)
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