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RECNO(3)                            Linux Programmer's Manual                            RECNO(3)

       recno - record number database access method

       #include <sys/types.h>
       #include <db.h>

       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:

                     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.

                     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.

                     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.

              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 the <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.

       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.

       Only big and little endian byte order is supported.

       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.

       This page is part of release 3.74 of the Linux man-pages project.  A  description  of  the
       project,  information  about  reporting  bugs, and the latest version of this page, can be
       found at http://www.kernel.org/doc/man-pages/.

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

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