NAME

       GDBM_File - Perl5 access to the gdbm library.

SYNOPSIS

           use GDBM_File;
           [$db =] tie %hash, 'GDBM_File', $filename, &GDBM_WRCREAT, 0640;
           # Use the %hash array.

           $e = $db->errno;
           $e = $db->syserrno;
           $str = $db->strerror;
           $bool = $db->needs_recovery;

           $db->clear_error;

           $db->reorganize;
           $db->sync;

           $n = $db->count;

           $n = $db->flags;

           $str = $db->dbname;

           $db->cache_size;
           $db->cache_size($newsize);

           $n = $db->block_size;

           $bool = $db->sync_mode;
           $db->sync_mode($bool);

           $bool = $db->centfree;
           $db->centfree($bool);

           $bool = $db->coalesce;
           $db->coalesce($bool);

           $bool = $db->mmap;

           $size = $db->mmapsize;
           $db->mmapsize($newsize);

           $db->recover(%args);

           untie %hash ;

DESCRIPTION

       GDBM_File is a module which allows Perl programs to make use of the facilities provided by
       the GNU gdbm library.  If you intend to use this module you should really have a copy of
       the gdbm manualpage at hand.

       Most of the libgdbm.a functions are available through the GDBM_File interface.

       Unlike Perl's built-in hashes, it is not safe to "delete" the current item from a
       GDBM_File tied hash while iterating over it with "each".  This is a limitation of the gdbm
       library.

STATIC METHODS

   GDBM_version
           $str = GDBM_File->GDBM_version;
           @ar = GDBM_File->GDBM_version;

       Returns the version number of the underlying libgdbm library. In scalar context, returns
       the library version formatted as string:

           MINOR.MAJOR[.PATCH][ (GUESS)]

       where MINOR, MAJOR, and PATCH are version numbers, and GUESS is a guess level (see below).

       In list context, returns a list:

           ( MINOR, MAJOR, PATCH [, GUESS] )

       The GUESS component is present only if libgdbm version is 1.8.3 or earlier. This is
       because earlier releases of libgdbm did not include information about their version and
       the GDBM_File module has to implement certain guesswork in order to determine it. GUESS is
       a textual description in string context, and a positive number indicating how rough the
       guess is in list context. Possible values are:

       1  - exact guess
           The major and minor version numbers are guaranteed to be correct. The actual
           patchlevel is most probably guessed right, but can be 1-2 less than indicated.

       2  - approximate
           The major and minor number are guaranteed to be correct. The patchlevel is set to the
           upper bound.

       3  - rough guess
           The version is guaranteed to be not newer than MAJOR.MINOR.

METHODS

   close
           $db->close;

       Closes the database. You are not advised to use this method directly. Please, use untie
       instead.

   errno
           $db->errno

       Returns the last error status associated with this database.

   syserrno
           $db->syserrno

       Returns the last system error status (C "errno" variable), associated with this database,

   strerror
           $db->strerror

       Returns textual description of the last error that occurred in this database.

   clear_error
           $db->clear_error

       Clear error status.

   needs_recovery
           $db->needs_recovery

       Returns true if the database needs recovery.

   reorganize
           $db->reorganize;

       Reorganizes the database.

   sync
           $db->sync;

       Synchronizes recent changes to the database with its disk copy.

   count
           $n = $db->count;

       Returns number of keys in the database.

   flags
           $db->flags;

       Returns flags passed as 4th argument to tie.

   dbname
           $db->dbname;

       Returns the database name (i.e. 3rd argument to tie.

   cache_size
           $db->cache_size;
           $db->cache_size($newsize);

       Returns the size of the internal GDBM cache for that database.

       Called with argument, sets the size to $newsize.

   block_size
           $db->block_size;

       Returns the block size of the database.

   sync_mode
           $db->sync_mode;
           $db->sync_mode($bool);

       Returns the status of the automatic synchronization mode. Called with argument, enables or
       disables the sync mode, depending on whether $bool is true or false.

       When synchronization mode is on (true), any changes to the database are immediately
       written to the disk. This ensures database consistency in case of any unforeseen errors
       (e.g. power failures), at the expense of considerable slowdown of operation.

       Synchronization mode is off by default.

   centfree
           $db->centfree;
           $db->centfree($bool);

       Returns status of the central free block pool (0 - disabled, 1 - enabled).

       With argument, changes its status.

       By default, central free block pool is disabled.

   coalesce
           $db->coalesce;
           $db->coalesce($bool);

   mmap
           $db->mmap;

       Returns true if memory mapping is enabled.

       This method will croak if the libgdbm library is complied without memory mapping support.

   mmapsize
           $db->mmapsize;
           $db->mmapsize($newsize);

       If memory mapping is enabled, returns the size of memory mapping. With argument, sets the
       size to $newsize.

       This method will croak if the libgdbm library is complied without memory mapping support.

   recover
           $db->recover(%args);

       Recovers data from a failed database. %args is optional and can contain following keys:

       err => sub { ... }
           Reference to code for detailed error reporting. Upon encountering an error, recover
           will call this sub with a single argument - a description of the error.

       backup => \$str
           Creates a backup copy of the database before recovery and returns its filename in
           $str.

       max_failed_keys => $n
           Maximum allowed number of failed keys. If the actual number becomes equal to $n,
           recover aborts and returns error.

       max_failed_buckets => $n
           Maximum allowed number of failed buckets. If the actual number becomes equal to $n,
           recover aborts and returns error.

       max_failures => $n
           Maximum allowed number of failures during recovery.

       stat => \%hash
           Return recovery statistics in %hash. Upon return, the following keys will be present:

           recovered_keys
                   Number of successfully recovered keys.

           recovered_buckets
                   Number of successfully recovered buckets.

           failed_keys
                   Number of keys that failed to be retrieved.

           failed_buckets
                   Number of buckets that failed to be retrieved.

AVAILABILITY

       gdbm is available from any GNU archive.  The master site is "ftp.gnu.org", but you are
       strongly urged to use one of the many mirrors.  You can obtain a list of mirror sites from
       <http://www.gnu.org/order/ftp.html>.

SECURITY AND PORTABILITY

       Do not accept GDBM files from untrusted sources.

       GDBM files are not portable across platforms.

       The GDBM documentation doesn't imply that files from untrusted sources can be safely used
       with "libgdbm".

       A maliciously crafted file might cause perl to crash or even expose a security
       vulnerability.

SEE ALSO

       perl(1), DB_File(3), perldbmfilter, gdbm(3),
       <https://www.gnu.org.ua/software/gdbm/manual.html>.