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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       The dbm() library has been superseded by ndbm (see ndbm(3C)).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	 func‐
       tions  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 data‐
       base 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 nex‐
       tkey(). 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.

SEE ALSO
       ar(1), cat(1), cc(1B), cp(1), tar(1), ndbm(3C)

NOTES
       Use of these interfaces should be restricted to only applications writ‐
       ten  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
       system 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 architec‐
       ture-specific (for example, they	 depend	 on  the  architecture's  byte
       order.)	These files are not guaranteed to be portable across architec‐
       tures.

SunOS 5.10			  30 Oct 2007			     dbm(3UCB)
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