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RocketLink!--> Man page versions:
DBM(3) OpenBSD Programmer's Manual DBM(3)
NAME
dbm, dbminit, fetch, store, delete, firstkey, nextkey, dbmclose -
database subroutines
SYNOPSIS
#include <dbm.h>
int
dbminit(const char *file);
int
dbmclose(void);
datum
fetch(datum key);
int
store(datum key, datum content);
int
delete(datum key);
datum
firstkey(void);
datum
nextkey(datum key);
DESCRIPTION
These functions provide a dbm-compatible interface to the database access
methods described in db(3). Each unique record in the database is a
key/content pair, the components of which may be any arbitrary binary da-
ta. The key and the content data are described by the datum data struc-
ture:
typedef struct {
char *dptr;
int dsize;
} datum
The dbminit() function is used to open a database. Before the call to
dbminit(), the files file.pag and file.dir must exist. The user is re-
sponsible for creating the zero-length .pag and .dir files.
Once the database is open, fetch() is used to retrieve the data content
associated with the key key. Similarly, store() is used to store the
content data with the key key.
The delete() function removes the key key and its associated content from
the database.
The functions firstkey() and nextkey() are used to iterate over all of
the records in the database. Each record will be reached exactly once,
but in no particular order. The firstkey() function returns the first
record of the database, and thereafter nextkey() returns the following
records. The following code traverses the entire database:
for (key = firstkey(); key.dptr != NULL; key = nextkey(key))
The behaviour of nextkey() is undefined if the database is modified after
a call to firstkey().
The database is closed with the dbmclose() function (you must close a
database before opening a new one).
Implementation notes
The underlying database is a hash(3) database with a bucket size of 4096,
a filling factor of 40, default hashing function and cache size, and uses
the host's native byte order.
RETURN VALUES
Upon successful completion, all functions that return int return a value
of 0, otherwise a negative value is returned.
Functions that return a datum indicate errors by setting the dptr field
to NULL.
SEE ALSO
db(3), hash(3), ndbm(3)
BUGS
Because the dbm routines are implemented on top of the db(3), only a
single file, file.pag, is used to actually store the database. The ref-
erences to file.dir are purely for backwards compatibility with historic
implementations.
OpenBSD 2.6 February 14, 1999 2
Source: OpenBSD 2.6 man pages. Copyright: Portions are copyrighted by BERKELEY SOFTWARE DESIGN, INC., The Regents of the University of California, Massachusetts Institute of Technology, Free Software Foundation, FreeBSD Inc., and others. |
(Corrections, notes, and links courtesy of RocketAware.com)
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