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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
       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(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
                     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(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
              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 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
              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
              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 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 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

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