recno man page on 4.4BSD

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RECNO(3)							      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 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  unmodi‐
		     fied 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 exam‐
	      ple, 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  cur‐
       rently 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),

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

BUGS
       Only big and little endian byte order is supported.

4.4 Berkeley Distribution	August 18, 1994			      RECNO(3)
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