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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;
  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 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, 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 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 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.

RESTRICTIONS
  Only big and little endian byte order is supported.

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.

RELATED INFORMATION
  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.

Index for Section 3

Alphabetical listing for R

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