delete(5)

                                               (BSD System Compatibility)

                                   dbm(3bsd)
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   dbm: dbminit, dbmclose, fetch, store, delete, firstkey, nextkey -- BSD
   database subroutines 

Synopsis

   /usr/ucb/cc [flag ... ] file ...
#include <dbm.h>

typedef struct {
    char *dptr;
    int dsize;
} datum;

dbminit(const char *file);

dbmclose(void);

datum fetch(datum key);

store(datum key, datum content);

delete(datum key);

datum firstkey(void);

datum nextkey(datum key);

Description

   These routines are provided for compatibility with applications
   originally written for BSD systems; new or ported applications should
   use the equivalent System V routines instead. See dbm(3rpc) and
   ndbm(3C).

References

   ``BSD system libraries and header files'' in Programming with system
   calls and libraries

   cc(1bsd), ld(1bsd), directory(3C), directory(3Cbsd) These functions
   maintain key/content pairs in a data base. The functions will handle
   very large (a billion blocks) databases and will access a keyed item
   in one or two file system accesses. The functions are obtained with
   the loader option -ldbm.

   keys and contents are described by the datum typedef. A datum
   specifies a string of dsize bytes pointed to by dptr. Arbitrary binary
   data, as well as normal ASCII strings, are allowed. The data base is
   stored in two files. One file is a directory containing a bit map and
   has .dir as its suffix. The second file contains all data and has .pag
   as its suffix.

   Before a database can be accessed, it must be opened by dbminit. At
   the time of this call, the files file.dir and file.pag must exist. An
   empty database is created by creating zero-length .dir and .pag files.

   A database may be closed by calling dbmclose. You must close a
   database before opening a new one.

   Once open, the data stored under a key is accessed by fetch and data
   is placed under a key by store. A key (and its associated contents) is
   deleted by delete. A linear pass through all keys in a database may be
   made, in an (apparently) random order, by use of firstkey and nextkey.
   firstkey will return the first key in the database. With any key
   nextkey will return the next key in the database. This code will
   traverse the data base:
   for (key = firstkey; key.dptr != NULL; key = nextkey(key))

Return values

   All functions that return an int indicate errors with negative values.
   A zero return indicates no error. Routines that return a datum
   indicate errors with a NULL (0) dptr.

References

   ``BSD system libraries and header files'' in Programming with system
   calls and libraries

   cc(1bsd), ld(1bsd), dbm(3rpc), ndbm(3C), ndbm(3bsd)

Notices

   The dbm library has been superseded by ndbm(3bsd), and is now
   implemented using ndbm.

   The .pag file will contain holes so that its apparent size is about
   four times its actual content. Older versions of the UNIX operating
   system may create real file blocks for these holes when touched. These
   files cannot be copied by normal means (that is, using cp(1), cat(1),
   tar(1), or ar(1)) without filling in the holes.

   dptr pointers returned by these subroutines point into static storage
   that is changed by subsequent calls.

   The sum of the sizes of a key/content pair must not exceed the
   internal block size (currently 1024 bytes). Moreover all key/content
   pairs that hash together must fit on a single block. store will return
   an error in the event that a disk block fills with inseparable data.

   delete does not physically reclaim file space, although it does make
   it available for reuse.

   The order of keys presented by firstkey and nextkey depends on a
   hashing function, not on anything interesting.

   There are no interlocks and no reliable cache flushing; thus
   concurrent updating and reading is risky.
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   © 2004 The SCO Group, Inc. All rights reserved.
   UnixWare 7 Release 7.1.4 - 25 April 2004
   
See also dbm(3rpc)