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dbm(3C)								       dbm(3C)

       dbminit,	 fetch,	 store, delete, firstkey, nextkey, dbmclose - database

       These functions maintain key/content pairs in a database.  They	handle
       very  large  (a	billion blocks (block = 1024 bytes)) databases and can
       locate a keyed item in one or two file system accesses.

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

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

       Once  open,  data  stored under a key is accessed by and data is placed
       under a key by Storing data on an existing key  replaces	 the  existing
       data.   A key (and its associated contents) is deleted by A linear pass
       through all keys in a database can  be  made,  in  (apparently)	random
       order  by  using	 and  returns the first key in the database.  With any
       key, returns the next key in the database.  The following code  can  be
       used to traverse the database:

       A  database  can be closed by calling A currently open database must be
       closed before opening a new one.

       All functions that return an indicate errors with negative  values  and
       success with zero.  Functions that return a indicate errors with a null

       The dbm functions provided in this library should not  be  confused  in
       any way with those of a general-purpose database management system such
       as ALLBASE/HP-UX SQL.  These functions provide for multiple search keys
       per  entry, they protect against multi-user access (in other words they
       do not lock records or files), and they provide the many	 other	useful
       data  base  functions that are found in more robust database management
       systems.	 Creating and updating databases by use of these functions  is
       relatively slow because of data copies that occur upon hash collisions.
       These functions for applications requiring fast	lookup	of  relatively
       static information that is to be indexed by a single key.

       The  file  will	contain	 holes so that its apparent size is about four
       times its actual content.  Some older UNIX  systems  create  real  file
       blocks  for  these holes when touched.  These files cannot be copied by
       normal means (such as cp(1), cat(1), tar(1), or ar(1))  without	expan‐

       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.  returns an error	 if  a
       disk block fills with inseparable data.

       does not physically reclaim file space, although it does make it avail‐
       able for reuse.

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

       A  or  during  a	 pass  through	the  keys  by and may yield unexpected

       dbm(3C) was developed by the University of California, Berkeley.



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