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 inter-
       faces.  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 applica-
		     tions 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 mem-
	      ory 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 ("
") 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, Mem-
       orandum No. UCB/ERL M82/32, May 1982.

COLOPHON

       This  page is part of release 4.15 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 https://www.kernel.org/doc/man-pages/.

4.4 Berkeley Distribution					    2017-09-15								  RECNO(3)