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gdbm ()
  • >> gdbm (3) ( Solaris man: Библиотечные вызовы )
  • gdbm (3) ( Linux man: Библиотечные вызовы )
  • Ключ gdbm обнаружен в базе ключевых слов.
         GDBM - The GNU database manager.  Includes dbm and ndbm com-
         patability. (Version 1.8.)
         #include <gdbm.h>
         extern gdbm_error
         extern char
         gdbm_open (name, block_size, read_write, mode, fatal_func)
         char * name;
         int block_size, read_write, mode;
         void (*fatal_func) ();
         gdbm_close (dbf)
         GDBM_FILE dbf;
         gdbm_store (dbf, key, content, flag)
         GDBM_FILE dbf;
         datum key, content;
         int flag;
         gdbm_fetch (dbf, key)
         GDBM_FILE dbf;
         datum key;
         gdbm_delete (dbf, key)
         GDBM_FILE dbf;
         datum key;
         gdbm_firstkey (dbf)
         GDBM_FILE dbf;
         gdbm_nextkey (dbf, key)
         GDBM_FILE dbf;
         datum key;
         gdbm_reorganize (dbf)
         GDBM_FILE dbf;
         gdbm_sync (dbf)
         GDBM_FILE dbf;
         gdbm_exists (dbf, key)
         GDBM_FILE dbf;
         datum key;
         char *
         gdbm_strerror (errno)
         gdbm_error errno;
         gdbm_setopt (dbf, option, value, size)
         GDBM_FILE dbf;
         int option;
         int *value;
         int size;
         gdbm_fdesc (dbf)
         GDBM_FILE dbf;
         DBM Compatability routines:
         #include <dbm.h>
         dbminit (name)
         char *name;
         store (key, content)
         datum key, content;
         fetch (key)
         datum key;
         delete (key)
         datum key;
         firstkey ()
         nextkey (key)
         datum key;
         dbmclose ()
         NDBM Compatability routines:
         #include <ndbm.h>
         *dbm_open (name, flags, mode)
         char *name;
         int flags, mode;
         dbm_close (file)
         DBM *file;
         dbm_fetch (file, key)
         DBM *file;
         datum key;
         dbm_store (file, key, content, flags)
         DBM *file;
         datum key, content;
         int flags;
         dbm_delete (file, key)
         DBM *file;
         datum key;
         dbm_firstkey (file)
         DBM *file;
         dbm_nextkey (file)
         DBM *file;
         dbm_error (file)
         DBM *file;
         dbm_clearerr (file)
         DBM *file;
         dbm_pagfno (file)
         DBM *file;
         dbm_dirfno (file)
         DBM *file;
         dbm_rdonly (file)
         DBM *file;
         GNU dbm is a library of routines  that  manages  data  files
         that contain key/data pairs.  The access provided is that of
         storing, retrieval, and deletion by  key  and  a  non-sorted
         traversal of all keys.  A process is allowed to use multiple
         data files at the same time.
         A process that opens a gdbm file is designated as a "reader"
         or  a  "writer".   Only  one writer may open a gdbm file and
         many readers may open the file.  Readers and writers can not
         open the gdbm file at the same time. The procedure for open-
         ing a gdbm file is:
           GDBM_FILE dbf;
           dbf = gdbm_open  (  name,  block_size,  read_write,  mode,
         fatal_func )
         Name is the name of the file (the complete name,  gdbm  does
         not  append any characters to this name).  Block_size is the
         size of a single transfer from disk to memory. This  parame-
         ter  is  ignored unless the file is a new file.  The minimum
         size is 512.  If it is less than 512, dbm will use the  stat
         block  size for the file system.  Read_write can have one of
         the following values:
         GDBM_READER reader
         GDBM_WRITER writer
         GDBM_WRCREAT writer - if database does not exist create  new
         GDBM_NEWDB writer - create new database  regardless  if  one
         For the last three (writers of the database)  the  following
         may  be added added to read_write by bitwise or:  GDBM_SYNC,
         which causes all database operations to be  synchronized  to
         the  disk,  and GDBM_NOLOCK, which prevents the library from
         performing any locking on the  database  file.   The  option
         GDBM_FAST  is  now  obsolete, since gdbm defaults to no-sync
         Mode is the file mode (see chmod(2) and open(2)) if the file
         is  created.  (*Fatal_func) () is a function for dbm to call
         if it detects a fatal error.  The  only  parameter  of  this
         function  is  a string.  If the value of 0 is provided, gdbm
         will use a default function.
         The return value dbf is the pointer needed by all other rou-
         tines  to  access that gdbm file.  If the return is the NULL
         pointer, gdbm_open was not successful.  The  errors  can  be
         found  in gdbm_errno for gdbm errors and in errno for system
         errors.  (For error codes, see gdbmerrno.h.)
         In all of the following calls, the parameter dbf  refers  to
         the pointer returned from gdbm_open.
         It is important that every file opened is also closed.  This
         is  needed  to  update  the reader/writer count on the file.
         This is done by:
           gdbm_close (dbf);
         The database is used  by  3  primary  routines.   The  first
         stores data in the database.
           ret = gdbm_store ( dbf, key, content, flag )
         Dbf is the pointer returned by gdbm_open.  Key  is  the  key
         data.   Content  is  the data to be associated with the key.
         Flag can have one of the following values:
         GDBM_INSERT insert only, generate an error if key exists
         GDBM_REPLACE replace contents if key exists.
         If a reader calls gdbm_store, the return value will be   -1.
         If  called  with GDBM_INSERT and key is in the database, the
         return value will be 1.  Otherwise, the return value is 0.
         NOTICE: If you store data for a key that is already  in  the
         data  base,  gdbm replaces the old data with the new data if
         called with GDBM_REPLACE.  You do not get two data items for
         the same key and you do not get an error from gdbm_store.
         NOTICE: The size in gdbm is not restricted like dbm or ndbm.
         Your data can be as large as you want.
         To search for some data:
           content = gdbm_fetch ( dbf, key )
         Dbf is the pointer returned by gdbm_open.  Key  is  the  key
         If the dptr element of the return value is NULL, no data was
         found.  Otherwise the return value is a pointer to the found
         data.  The storage space for the dptr element  is  allocated
         using  malloc(3C).   Gdbm  does  not automatically free this
         data.  It is the programmer's responsibility  to  free  this
         storage when it is no longer needed.
         To search for some data, without retrieving it:
           ret = gdbm_exists ( dbf, key )
         Dbf is the pointer returned by gdbm_open.  Key  is  the  key
         data to search for.
         If the key is found within the database,  the  return  value
         ret  will be true.  If nothing appropiate is found, ret will
         be false.  This routine is useful for checking for the exis-
         tance  of a record, without performing the memory allocation
         done by gdbm_fetch.
         To remove some data from the database:
           ret = gdbm_delete ( dbf, key )
         Dbf is the pointer returned by gdbm_open.  Key  is  the  key
         The return value is -1 if the item is  not  present  or  the
         requester is a reader.  The return value is 0 if there was a
         successful delete.
         The next two routines allow for accessing all items  in  the
         database.   This  access  is  not  key sequential, but it is
         guaranteed to visit every key in the  database  once.   (The
         order has to do with the hash values.)
           key = gdbm_firstkey ( dbf )
           nextkey = gdbm_nextkey ( dbf, key )
         Dbf is the pointer returned by gdbm_open.  Key  is  the  key
         The return values are both of type datum.  If the dptr  ele-
         ment  of  the return value is NULL, there is no first key or
         next key.  Again notice that dptr points to  data  allocated
         by malloc(3C) and gdbm will not free it for you.
         These functions were  intended  to  visit  the  database  in
         read-only algorithms, for instance, to validate the database
         or similar operations.
         File `visiting' is based on  a  `hash  table'.   gdbm_delete
         re-arranges  the hash table to make sure that any collisions
         in the table do not leave some item `un-findable'.  The ori-
         ginal key order is NOT guaranteed to remain unchanged in ALL
         instances.  It is possible that some key will not be visited
         if a loop like the following is executed:
            key = gdbm_firstkey ( dbf );
            while ( key.dptr ) {
               nextkey = gdbm_nextkey ( dbf, key );
               if ( some condition ) {
                  gdbm_delete ( dbf, key );
                  free ( key.dptr );
               key = nextkey;
         The following routine should be used very infrequently.
           ret = gdbm_reorganize ( dbf )
         If you have had a lot of deletions and would like to  shrink
         the  space used by the gdbm file, this routine will reorgan-
         ize the database.  Gdbm will not shorten  the  length  of  a
         gdbm  file  except  by  using this reorganization.  (Deleted
         file space will be reused.)
         Unless your database was opened  with  the  GDBM_SYNC  flag,
         gdbm  does  not  wait  for  writes to be flushed to the disk
         before continuing.  The following routine  can  be  used  to
         guarantee  that  the  database  is physically written to the
         disk file.
           gdbm_sync ( dbf )
         It will not return until the disk file state is  syncronized
         with the in-memory state of the database.
         To convert a gdbm error code into  English  text,  use  this
           ret = gdbm_strerror ( errno )
         Where errno is of type gdbm_error, usually the global  vari-
         able gdbm_errno.  The appropiate phrase is returned.
         Gdbm now supports the ability to set certain options  on  an
         already open database.
           ret = gdbm_setopt ( dbf, option, value, size )
         Where dbf is the  return  value  from  a  previous  call  to
         gdbm_open,  and  option  specifies which option to set.  The
         valid options are currently:
           GDBM_CACHESIZE - Set the size of the internal bucket
           cache. This option may only be set once on each GDBM_FILE
           descriptor, and is set automatically to 100 upon the first
           access to the database.
           GDBM_FASTMODE - Set fast mode to either on or off.  This
           allows fast mode to be toggled on an already open and
           active database. value (see below) should be set to either
           TRUE or FALSE.  This option is now obsolete.
           GDBM_SYNCMODE - Turn on or off file system synchronization
           This setting defaults to off; value (see below) should  be
         set to either
           TRUE or FALSE.
           GDBM_CENTFREE - Set central free block pool to  either  on
         or off.
           The default is off, which is how previous versions of Gdbm
           handled free blocks. If set, this option causes all subse-
         quent free
           blocks to be placed  in  the  global  pool,  allowing  (in
           more file space to be  reused  more  quickly.  value  (see
         below) should
           be set to either TRUE or FALSE.
           NOTICE: This feature is still under study.
           GDBM_COALESCEBLKS - Set free block merging to either on or
           The default is off, which is how previous versions of Gdbm
           handled free blocks. If set, this option  causes  adjacent
         free blocks
           to be merged. This can become a CPU expensive process with
         time, though,
           especially if  used  in  conjunction  with  GDBM_CENTFREE.
           (see below) should be set to either TRUE or FALSE.
           NOTICE: This feature is still under study.
         value is the value to set option to, specified as an integer
         pointer.   size is the size of the data pointed to by value.
         The return value will be -1 upon failure, or 0 upon success.
         The global variable gdbm_errno will be set upon failure.
         For instance, to set a database to use a cache of 10,  after
         opening  it with gdbm_open, but prior to accessing it in any
         way, the following code could be used:
           int value = 10;
           ret   =   gdbm_setopt(   dbf,   GDBM_CACHESIZE,    &value,
         If the database was opened with the  GDBM_NOLOCK  flag,  the
         user may wish to perform their own file locking on the data-
         base file in order to prevent multiple writers operating  on
         the same file simultaneously.
         In order to support this, the  gdbm_fdesc  routine  is  pro-
           ret = gdbm_fdesc ( dbf )
         Where dbf is the  return  value  from  a  previous  call  to
         gdbm_open.   The return value will be the file descriptor of
         the database.
         The following two external variables may be useful:
         gdbm_errno is the variable that  contains  more  information
         about gdbm errors.  (gdbm.h has the definitions of the error
         values and defines gdbm_errno as an external variable.)
         gdbm_version is the string containing the  version  informa-
         There are a few more things of interest.  First, gdbm  files
         are  not  "sparse".   You  can copy them with the UNIX cp(1)
         command and they will not expand  in  the  copying  process.
         Also,  there  is  a compatibility mode for use with programs
         that already use UNIX dbm.  In this compatibility  mode,  no
         gdbm  file  pointer  is required by the programmer, and only
         one file may be opened at a time.  All users in  compatibil-
         ity  mode  are assumed to be writers.  If the gdbm file is a
         read only, it will fail as a writer, but will  also  try  to
         open  it as a reader.  All returned pointers in datum struc-
         tures point to data that gdbm WILL  free.   They  should  be
         treated as static pointers (as standard UNIX dbm does).
         This library is accessed by specifying -lgdbm  as  the  last
         parameter to the compile line, e.g.:
              gcc -o prog prog.c -lgdbm
         dbm, ndbm
         by Philip A. Nelson and Jason Downs.  Copyright (C)  1990  -
         1999 Free Software Foundation, Inc.
         GDBM is free software; you can redistribute it and/or modify
         it under the terms of the GNU General Public License as pub-
         lished by the Free Software Foundation; either version 1, or
         (at your option) any later version.
         GDBM is distributed in the hope that it will be useful,  but
         WITHOUT  ANY  WARRANTY; without even the implied warranty of
         the GNU General Public License for more details.
         You should have received a copy of the  GNU  General  Public
         License  along  with  GDBM;  see  the file COPYING.  If not,
         write to the Free Software Foundation, 675  Mass  Ave,  Cam-
         bridge, MA 02139, USA.
         You may contact the original author by:
           us-mail:  Philip A. Nelson
         Computer Science Department
         Western Washington University
         Bellingham, WA 98226
         You may contact the current maintainer by:

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