dbm(3UCB)					     SunOS/BSD Compatibility Library Functions						 dbm(3UCB)

NAME

       dbm, dbminit, dbmclose, fetch, store, delete, firstkey, nextkey - data base subroutines

SYNOPSIS

       /usr/ucb/cc [ flag ... ] file ... -ldbm
       #include <dbm.h>
       typedef struct {
	    char *dptr;
	    int dsize;
	}datum;

       int dbminit(file);
       char *file;

       int dbmclose();

       datum fetch( key);
       datum key;

       int store( key, dat);
       datum key, dat;

       int delete(key);
       datum key;
       datum firstkey()

       datum nextkey(key);
       datum key;

DESCRIPTION

       The dbm() library has been superseded by ndbm (see ndbm(3C)).

       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.

       key/dat and their content 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 indi-
       cate errors with a NULL(0) dptr.

SEE ALSO

       ar(1), cat(1), cp(1), tar(1), ndbm(3C)

NOTES

       Use of these interfaces should be restricted to only applications written on BSD platforms.  Use of these interfaces with any of the system
       libraries or in multi-thread applications is unsupported.

       The .pag file will contain holes so that its apparent size may be larger than its actual content. Older versions of the UNIX operating sys-
       tem  may create real file blocks for these holes when touched. These files cannot be copied by normal means ( cp(1), cat(1), tar(1), 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.

       The  database  files  (file.dir and file.pag) are binary and are architecture-specific (for example, they depend on the architecture's byte
       order.)	These files are not guaranteed to be portable across architectures.

SunOS 5.10							    20 Feb 1997 							 dbm(3UCB)