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Rob Kinyon > DBM-Deep-2.0011 > DBM::Deep



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Module Version: 2.0011   Source   Latest Release: DBM-Deep-2.0016


DBM::Deep - A pure perl multi-level hash/array DBM that supports transactions




  use DBM::Deep;
  my $db = DBM::Deep->new( "foo.db" );

  $db->{key} = 'value';
  print $db->{key};

  $db->put('key' => 'value');
  print $db->get('key');

  # true multi-level support
  $db->{my_complex} = [
      'hello', { perl => 'rules' },
      42, 99,


  # Do stuff here


  tie my %db, 'DBM::Deep', 'foo.db';
  $db{key} = 'value';
  print $db{key};

  tied(%db)->put('key' => 'value');
  print tied(%db)->get('key');


A unique flat-file database module, written in pure perl. True multi-level hash/array support (unlike MLDBM, which is faked), hybrid OO / tie() interface, cross-platform FTPable files, ACID transactions, and is quite fast. Can handle millions of keys and unlimited levels without significant slow-down. Written from the ground-up in pure perl -- this is NOT a wrapper around a C-based DBM. Out-of-the-box compatibility with Unix, Mac OS X and Windows.


NOTE: 2.0000 introduces Unicode support in the File back end. This necessitates a change in the file format. The version 1.0003 format is still supported, though, so we have added a db_version() method. If you are using a database in the old format, you will have to upgrade it to get Unicode support.

NOTE: 1.0020 introduces different engines which are backed by different types of storage. There is the original storage (called 'File') and a database storage (called 'DBI'). q.v. "PLUGINS" for more information.

NOTE: 1.0000 has significant file format differences from prior versions. There is a backwards-compatibility layer at utils/ Files created by 1.0000 or higher are NOT compatible with scripts using prior versions.


DBM::Deep is a wrapper around different storage engines. These are:


This is the traditional storage engine, storing the data to a custom file format. The parameters accepted are:

When you open an existing database file, the version of the database format will stay the same. But if you are creating a new file, it will be in the latest format.


This is a storage engine that stores the data in a relational database. Funnily enough, this engine doesn't work with transactions (yet) as InnoDB doesn't do what DBM::Deep needs it to do.

The parameters accepted are:

NOTE: This has only been tested with MySQL and SQLite (with disappointing results). I plan on extending this to work with PostgreSQL in the near future. Oracle, Sybase, and other engines will come later.

Planned engines

There are plans to extend this functionality to (at least) the following:


Construction can be done OO-style (which is the recommended way), or using Perl's tie() function. Both are examined here.

OO Construction

The recommended way to construct a DBM::Deep object is to use the new() method, which gets you a blessed and tied hash (or array) reference.

  my $db = DBM::Deep->new( "foo.db" );

This opens a new database handle, mapped to the file "foo.db". If this file does not exist, it will automatically be created. DB files are opened in "r+" (read/write) mode, and the type of object returned is a hash, unless otherwise specified (see "Options" below).

You can pass a number of options to the constructor to specify things like locking, autoflush, etc. This is done by passing an inline hash (or hashref):

  my $db = DBM::Deep->new(
      file      => "foo.db",
      locking   => 1,
      autoflush => 1

Notice that the filename is now specified inside the hash with the "file" parameter, as opposed to being the sole argument to the constructor. This is required if any options are specified. See "Options" below for the complete list.

You can also start with an array instead of a hash. For this, you must specify the type parameter:

  my $db = DBM::Deep->new(
      file => "foo.db",
      type => DBM::Deep->TYPE_ARRAY

Note: Specifying the type parameter only takes effect when beginning a new DB file. If you create a DBM::Deep object with an existing file, the type will be loaded from the file header, and an error will be thrown if the wrong type is passed in.

Tie Construction

Alternately, you can create a DBM::Deep handle by using Perl's built-in tie() function. The object returned from tie() can be used to call methods, such as lock() and unlock(). (That object can be retrieved from the tied variable at any time using tied() - please see perltie for more info.)

  my %hash;
  my $db = tie %hash, "DBM::Deep", "foo.db";

  my @array;
  my $db = tie @array, "DBM::Deep", "bar.db";

As with the OO constructor, you can replace the DB filename parameter with a hash containing one or more options (see "Options" just below for the complete list).

  tie %hash, "DBM::Deep", {
      file => "foo.db",
      locking => 1,
      autoflush => 1


There are a number of options that can be passed in when constructing your DBM::Deep objects. These apply to both the OO- and tie- based approaches.

The following parameters may be specified in the constructor the first time the datafile is created. However, they will be stored in the header of the file and cannot be overridden by subsequent openings of the file - the values will be set from the values stored in the datafile's header.


With DBM::Deep you can access your databases using Perl's standard hash/array syntax. Because all DBM::Deep objects are tied to hashes or arrays, you can treat them as such (but see "external_refs", above, and "Stale References", below). DBM::Deep will intercept all reads/writes and direct them to the right place -- the DB file. This has nothing to do with the "Tie Construction" section above. This simply tells you how to use DBM::Deep using regular hashes and arrays, rather than calling functions like get() and put() (although those work too). It is entirely up to you how to want to access your databases.


You can treat any DBM::Deep object like a normal Perl hash reference. Add keys, or even nested hashes (or arrays) using standard Perl syntax:

  my $db = DBM::Deep->new( "foo.db" );

  $db->{mykey} = "myvalue";
  $db->{myhash} = {};
  $db->{myhash}->{subkey} = "subvalue";

  print $db->{myhash}->{subkey} . "\n";

You can even step through hash keys using the normal Perl keys() function:

  foreach my $key (keys %$db) {
      print "$key: " . $db->{$key} . "\n";

Remember that Perl's keys() function extracts every key from the hash and pushes them onto an array, all before the loop even begins. If you have an extremely large hash, this may exhaust Perl's memory. Instead, consider using Perl's each() function, which pulls keys/values one at a time, using very little memory:

  while (my ($key, $value) = each %$db) {
      print "$key: $value\n";

Please note that when using each(), you should always pass a direct hash reference, not a lookup. Meaning, you should never do this:

  while (my ($key, $value) = each %{$db->{foo}}) { # BAD

This causes an infinite loop, because for each iteration, Perl is calling FETCH() on the $db handle, resulting in a "new" hash for foo every time, so it effectively keeps returning the first key over and over again. Instead, assign a temporary variable to $db->{foo}, then pass that to each().


As with hashes, you can treat any DBM::Deep object like a normal Perl array reference. This includes inserting, removing and manipulating elements, and the push(), pop(), shift(), unshift() and splice() functions. The object must have first been created using type DBM::Deep->TYPE_ARRAY, or simply be a nested array reference inside a hash. Example:

  my $db = DBM::Deep->new(
      file => "foo-array.db",
      type => DBM::Deep->TYPE_ARRAY

  $db->[0] = "foo";
  push @$db, "bar", "baz";
  unshift @$db, "bah";

  my $last_elem   = pop @$db;   # baz
  my $first_elem  = shift @$db; # bah
  my $second_elem = $db->[1];   # bar

  my $num_elements = scalar @$db;


In addition to the tie() interface, you can also use a standard OO interface to manipulate all aspects of DBM::Deep databases. Each type of object (hash or array) has its own methods, but both types share the following common methods: put(), get(), exists(), delete() and clear(). fetch() and store() are aliases to put() and get(), respectively.


For hashes, DBM::Deep supports all the common methods described above, and the following additional methods: first_key() and next_key().

Here are some examples of using hashes:

  my $db = DBM::Deep->new( "foo.db" );

  $db->put("foo", "bar");
  print "foo: " . $db->get("foo") . "\n";

  $db->put("baz", {}); # new child hash ref
  $db->get("baz")->put("buz", "biz");
  print "buz: " . $db->get("baz")->get("buz") . "\n";

  my $key = $db->first_key();
  while ($key) {
      print "$key: " . $db->get($key) . "\n";
      $key = $db->next_key($key);

  if ($db->exists("foo")) { $db->delete("foo"); }


For arrays, DBM::Deep supports all the common methods described above, and the following additional methods: length(), push(), pop(), shift(), unshift() and splice().

Here are some examples of using arrays:

  my $db = DBM::Deep->new(
      file => "foo.db",
      type => DBM::Deep->TYPE_ARRAY

  $db->push("bar", "baz");
  $db->put(3, "buz");

  my $len = $db->length();
  print "length: $len\n"; # 4

  for (my $k=0; $k<$len; $k++) {
      print "$k: " . $db->get($k) . "\n";

  $db->splice(1, 2, "biz", "baf");

  while (my $elem = shift @$db) {
      print "shifted: $elem\n";


Enable or disable automatic file locking by passing a boolean value to the locking parameter when constructing your DBM::Deep object (see "SETUP" above).

  my $db = DBM::Deep->new(
      file => "foo.db",
      locking => 1

This causes DBM::Deep to flock() the underlying filehandle with exclusive mode for writes, and shared mode for reads. This is required if you have multiple processes accessing the same database file, to avoid file corruption. Please note that flock() does NOT work for files over NFS. See "DB over NFS" below for more.

Explicit Locking

You can explicitly lock a database, so it remains locked for multiple actions. This is done by calling the lock_exclusive() method (for when you want to write) or the lock_shared() method (for when you want to read). This is particularly useful for things like counters, where the current value needs to be fetched, then incremented, then stored again.

  my $counter = $db->get("counter");
  $db->put("counter", $counter);

  # or...



Due to Win32 actually enforcing the read-only status of a shared lock, all locks on Win32 and cygwin are exclusive. This is because of how autovivification currently works. Hopefully, this will go away in a future release.


You can import existing complex structures by calling the import() method, and export an entire database into an in-memory structure using the export() method. Both are examined here.


Say you have an existing hash with nested hashes/arrays inside it. Instead of walking the structure and adding keys/elements to the database as you go, simply pass a reference to the import() method. This recursively adds everything to an existing DBM::Deep object for you. Here is an example:

  my $struct = {
      key1 => "value1",
      key2 => "value2",
      array1 => [ "elem0", "elem1", "elem2" ],
      hash1 => {
          subkey1 => "subvalue1",
          subkey2 => "subvalue2"

  my $db = DBM::Deep->new( "foo.db" );
  $db->import( $struct );

  print $db->{key1} . "\n"; # prints "value1"

This recursively imports the entire $struct object into $db, including all nested hashes and arrays. If the DBM::Deep object contains existing data, keys are merged with the existing ones, replacing if they already exist. The import() method can be called on any database level (not just the base level), and works with both hash and array DB types.

Note: Make sure your existing structure has no circular references in it. These will cause an infinite loop when importing. There are plans to fix this in a later release.


Calling the export() method on an existing DBM::Deep object will return a reference to a new in-memory copy of the database. The export is done recursively, so all nested hashes/arrays are all exported to standard Perl objects. Here is an example:

  my $db = DBM::Deep->new( "foo.db" );

  $db->{key1} = "value1";
  $db->{key2} = "value2";
  $db->{hash1} = {};
  $db->{hash1}->{subkey1} = "subvalue1";
  $db->{hash1}->{subkey2} = "subvalue2";

  my $struct = $db->export();

  print $struct->{key1} . "\n"; # prints "value1"

This makes a complete copy of the database in memory, and returns a reference to it. The export() method can be called on any database level (not just the base level), and works with both hash and array DB types. Be careful of large databases -- you can store a lot more data in a DBM::Deep object than an in-memory Perl structure.

Note: Make sure your database has no circular references in it. These will cause an infinite loop when exporting. There are plans to fix this in a later release.


DBM::Deep has a number of hooks where you can specify your own Perl function to perform filtering on incoming or outgoing data. This is a perfect way to extend the engine, and implement things like real-time compression or encryption. Filtering applies to the base DB level, and all child hashes / arrays. Filter hooks can be specified when your DBM::Deep object is first constructed, or by calling the set_filter() method at any time. There are four available filter hooks.


This method takes two parameters - the filter type and the filter subreference. The four types are:

Here are the two ways to setup a filter hook:

  my $db = DBM::Deep->new(
      file => "foo.db",
      filter_store_value => \&my_filter_store,
      filter_fetch_value => \&my_filter_fetch

  # or...

  $db->set_filter( "store_value", \&my_filter_store );
  $db->set_filter( "fetch_value", \&my_filter_fetch );

Your filter function will be called only when dealing with SCALAR keys or values. When nested hashes and arrays are being stored/fetched, filtering is bypassed. Filters are called as static functions, passed a single SCALAR argument, and expected to return a single SCALAR value. If you want to remove a filter, set the function reference to undef:

  $db->set_filter( "store_value", undef );


Please read DBM::Deep::Cookbook for examples of filters.


Most DBM::Deep methods return a true value for success, and call die() on failure. You can wrap calls in an eval block to catch the die.

  my $db = DBM::Deep->new( "foo.db" ); # create hash
  eval { $db->push("foo"); }; # ILLEGAL -- push is array-only call

  print $@;           # prints error message


If you have a 64-bit system, and your Perl is compiled with both LARGEFILE and 64-bit support, you may be able to create databases larger than 4 GB. DBM::Deep by default uses 32-bit file offset tags, but these can be changed by specifying the 'pack_size' parameter when constructing the file.

      file      => $filename,
      pack_size => 'large',

This tells DBM::Deep to pack all file offsets with 8-byte (64-bit) quad words instead of 32-bit longs. After setting these values your DB files have a theoretical maximum size of 16 XB (exabytes).

You can also use pack_size => 'small' in order to use 16-bit file offsets.

Note: Changing these values will NOT work for existing database files. Only change this for new files. Once the value has been set, it is stored in the file's header and cannot be changed for the life of the file. These parameters are per-file, meaning you can access 32-bit and 64-bit files, as you choose.

Note: We have not personally tested files larger than 4 GB -- all our systems have only a 32-bit Perl. However, we have received user reports that this does indeed work.


If you require low-level access to the underlying filehandle that DBM::Deep uses, you can call the _fh() method, which returns the handle:

  my $fh = $db->_fh();

This method can be called on the root level of the database, or any child hashes or arrays. All levels share a root structure, which contains things like the filehandle, a reference counter, and all the options specified when you created the object. You can get access to this file object by calling the _storage() method.

  my $file_obj = $db->_storage();

This is useful for changing options after the object has already been created, such as enabling/disabling locking. You can also store your own temporary user data in this structure (be wary of name collision), which is then accessible from any child hash or array.


DBM::Deep has full support for circular references. Meaning you can have a nested hash key or array element that points to a parent object. This relationship is stored in the DB file, and is preserved between sessions. Here is an example:

  my $db = DBM::Deep->new( "foo.db" );

  $db->{foo} = "bar";
  $db->{circle} = $db; # ref to self

  print $db->{foo} . "\n"; # prints "bar"
  print $db->{circle}->{foo} . "\n"; # prints "bar" again

This also works as expected with array and hash references. So, the following works as expected:

  $db->{foo} = [ 1 .. 3 ];
  $db->{bar} = $db->{foo};

  push @{$db->{foo}}, 42;
  is( $db->{bar}[-1], 42 ); # Passes

This, however, does not extend to assignments from one DB file to another. So, the following will throw an error:

  my $db1 = DBM::Deep->new( "foo.db" );
  my $db2 = DBM::Deep->new( "bar.db" );

  $db1->{foo} = [];
  $db2->{foo} = $db1->{foo}; # dies

Note: Passing the object to a function that recursively walks the object tree (such as Data::Dumper or even the built-in optimize() or export() methods) will result in an infinite loop. This will be fixed in a future release by adding singleton support.


As of 1.0000, DBM::Deep has ACID transactions. Every DBM::Deep object is completely transaction-ready - it is not an option you have to turn on. You do have to specify how many transactions may run simultaneously (q.v. "num_txns").

Three new methods have been added to support them. They are:

Transactions in DBM::Deep are done using a variant of the MVCC method, the same method used by the InnoDB MySQL engine.


As of 1.0000, the file format has changed. To aid in upgrades, a migration script is provided within the CPAN distribution, called utils/

NOTE: This script is not installed onto your system because it carries a copy of every version prior to the current version.

As of version 2.0000, databases created by old versions back to 1.0003 can be read, but new features may not be available unless the database is upgraded first.


The following are items that are planned to be added in future releases. These are separate from the "CAVEATS, ISSUES & BUGS" below.


Right now, you cannot run a transaction within a transaction. Removing this restriction is technically straightforward, but the combinatorial explosion of possible usecases hurts my head. If this is something you want to see immediately, please submit many testcases.


If a client is willing to assert upon opening the file that this process will be the only consumer of that datafile, then there are a number of caching possibilities that can be taken advantage of. This does, however, mean that DBM::Deep is more vulnerable to losing data due to unflushed changes. It also means a much larger in-memory footprint. As such, it's not clear exactly how this should be done. Suggestions are welcome.


The techniques used in DBM::Deep simply require a seekable contiguous datastore. This could just as easily be a large string as a file. By using substr, the STM capabilities of DBM::Deep could be used within a single-process. I have no idea how I'd specify this, though. Suggestions are welcome.

Different contention resolution mechanisms

Currently, the only contention resolution mechanism is last-write-wins. This is the mechanism used by most RDBMSes and should be good enough for most uses. For advanced uses of STM, other contention mechanisms will be needed. If you have an idea of how you'd like to see contention resolution in DBM::Deep, please let me know.


This section describes all the known issues with DBM::Deep. These are issues that are either intractable or depend on some feature within Perl working exactly right. It you have found something that is not listed below, please send an e-mail to Likewise, if you think you know of a way around one of these issues, please let me know.


(The following assumes a high level of Perl understanding, specifically of references. Most users can safely skip this section.)

Currently, the only references supported are HASH and ARRAY. The other reference types (SCALAR, CODE, GLOB, and REF) cannot be supported for various reasons.

External references and transactions

If you do my $x = $db->{foo};, then start a transaction, $x will be referencing the database from outside the transaction. A fix for this (and other issues with how external references into the database) is being looked into. This is the skipped set of tests in t/39_singletons.t and a related issue is the focus of t/37_delete_edge_cases.t

File corruption

The current level of error handling in DBM::Deep is minimal. Files are checked for a 32-bit signature when opened, but any other form of corruption in the datafile can cause segmentation faults. DBM::Deep may try to seek() past the end of a file, or get stuck in an infinite loop depending on the level and type of corruption. File write operations are not checked for failure (for speed), so if you happen to run out of disk space, DBM::Deep will probably fail in a bad way. These things will be addressed in a later version of DBM::Deep.

DB over NFS

Beware of using DBM::Deep files over NFS. DBM::Deep uses flock(), which works well on local filesystems, but will NOT protect you from file corruption over NFS. I've heard about setting up your NFS server with a locking daemon, then using lockf() to lock your files, but your mileage may vary there as well. From what I understand, there is no real way to do it. However, if you need access to the underlying filehandle in DBM::Deep for using some other kind of locking scheme like lockf(), see the "LOW-LEVEL ACCESS" section above.

Copying Objects

Beware of copying tied objects in Perl. Very strange things can happen. Instead, use DBM::Deep's clone() method which safely copies the object and returns a new, blessed and tied hash or array to the same level in the DB.

  my $copy = $db->clone();

Note: Since clone() here is cloning the object, not the database location, any modifications to either $db or $copy will be visible to both.

Stale References

If you take a reference to an array or hash from the database, it is tied to the database itself. This means that if the datum in question is subsequently deleted from the database, the reference to it will point to an invalid location and unpredictable things will happen if you try to use it.

So a seemingly innocuous piece of code like this:

  my %hash = %{ $db->{some_hash} };

can fail if another process deletes or clobbers $db->{some_hash} while the data are being extracted, since %{ ... } is not atomic. (This actually happened.) The solution is to lock the database before reading the data:

  my %hash = %{ $db->{some_hash} };

As of version 1.0024, if you assign a stale reference to a location in the database, DBM::Deep will warn, if you have uninitialized warnings enabled, and treat the stale reference as undef. An attempt to use a stale reference as an array or hash reference will cause an error.

Large Arrays

Beware of using shift(), unshift() or splice() with large arrays. These functions cause every element in the array to move, which can be murder on DBM::Deep, as every element has to be fetched from disk, then stored again in a different location. This will be addressed in a future version.

This has been somewhat addressed so that the cost is constant, regardless of what is stored at those locations. So, small arrays with huge data structures in them are faster. But, large arrays are still large.

Writeonly Files

If you pass in a filehandle to new(), you may have opened it in either a readonly or writeonly mode. STORE will verify that the filehandle is writable. However, there doesn't seem to be a good way to determine if a filehandle is readable. And, if the filehandle isn't readable, it's not clear what will happen. So, don't do that.

Assignments Within Transactions

The following will not work as one might expect:

  my $x = { a => 1 };

  $db->{foo} = $x;

  is( $x->{a}, 1 ); # This will fail!

The problem is that the moment a reference used as the rvalue to a DBM::Deep object's lvalue, it becomes tied itself. This is so that future changes to $x can be tracked within the DBM::Deep file and is considered to be a feature. By the time the rollback occurs, there is no knowledge that there had been an $x or what memory location to assign an export() to.

NOTE: This does not affect importing because imports do a walk over the reference to be imported in order to explicitly leave it untied.


Devel::Cover is used to test the code coverage of the tests. Below is the Devel::Cover report on this distribution's test suite.

  ---------------------------- ------ ------ ------ ------ ------ ------ ------
  File                           stmt   bran   cond    sub    pod   time  total
  ---------------------------- ------ ------ ------ ------ ------ ------ ------
  blib/lib/DBM/          100.0   89.1   82.9  100.0  100.0   32.5   98.1
  blib/lib/DBM/Deep/    100.0   94.4  100.0  100.0  100.0    5.2   98.8
  blib/lib/DBM/Deep/   100.0   92.9  100.0  100.0  100.0    7.4  100.0
  ...ib/DBM/Deep/Engine/   95.0   73.1  100.0  100.0  100.0    1.5   90.4
  ...b/DBM/Deep/Engine/   92.3   78.5   88.9  100.0  100.0    4.9   90.3
  blib/lib/DBM/Deep/     100.0  100.0  100.0  100.0  100.0    3.8  100.0
  .../lib/DBM/Deep/  100.0    n/a    n/a  100.0  100.0    0.0  100.0
  .../DBM/Deep/Iterator/  100.0  100.0    n/a  100.0  100.0    1.2  100.0
  ...DBM/Deep/Iterator/   92.5   84.6    n/a  100.0   66.7    0.6   90.0
  ...erator/File/  100.0   75.0    n/a  100.0   66.7    0.4   93.8
  ...ep/Iterator/File/  100.0  100.0    n/a  100.0  100.0    0.2  100.0
  blib/lib/DBM/Deep/      87.5    n/a    n/a   75.0    n/a    0.0   83.3
  blib/lib/DBM/Deep/    91.7    n/a    n/a   83.3    0.0    6.7   74.4
  ...ib/DBM/Deep/Sector/   96.8   83.3    n/a  100.0    0.0    1.0   89.8
  ...p/Sector/DBI/  100.0   95.5  100.0  100.0    0.0    2.2   91.2
  ...Deep/Sector/DBI/  100.0  100.0    n/a  100.0    0.0    1.1   92.9
  ...b/DBM/Deep/Sector/   96.0   87.5  100.0   92.3   25.0    2.2   91.0
  ...Sector/File/   98.2   85.7   83.3  100.0    0.0    3.3   89.4
  .../Deep/Sector/File/  100.0    n/a    n/a  100.0    0.0    0.1   90.9
  ...Deep/Sector/File/  100.0   80.0   33.3  100.0    0.0    0.8   83.1
  .../Deep/Sector/File/  100.0  100.0    n/a  100.0    0.0    0.0   91.7
  .../Sector/File/  100.0   90.0   80.0  100.0    0.0    1.4   91.5
  ...eep/Sector/File/   98.4   87.5    n/a  100.0    0.0    0.8   91.9
  blib/lib/DBM/Deep/  100.0    n/a    n/a  100.0  100.0    0.0  100.0
  ...b/DBM/Deep/Storage/   97.3   70.8    n/a  100.0   38.5    6.7   87.0
  .../DBM/Deep/Storage/   96.6   77.1   80.0   95.7  100.0   16.0   91.8
  Total                          99.3   85.2   84.9   99.8   63.3  100.0   97.6
  ---------------------------- ------ ------ ------ ------ ------ ------ ------


Check out the DBM::Deep Google Group at or send email to You can also visit #dbm-deep on

The source code repository is at


Rob Kinyon,

Originally written by Joseph Huckaby,


Stonehenge Consulting ( sponsored the development of transactions and freespace management, leading to the 1.0000 release. A great debt of gratitude goes out to them for their continuing leadership in and support of the Perl community.


The following have contributed greatly to make DBM::Deep what it is today:



perltie(1), Tie::Hash(3), Fcntl(3), flock(2), lockf(3), nfs(5)


Copyright (c) 2007-14 Rob Kinyon. All Rights Reserved. This is free software, you may use it and distribute it under the same terms as Perl itself.

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