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Database Support
Perl provides a basic database capability called DBM which stores a hash in two files - a .dir file that contains the hash keys and a .pag file that contains the values corresponding to the keys.

Open/Close

dbmclose, dbmopen, tie, untie

Database Handling Syntax
To open a database, use the dbmopen function.

     dbmopen (%myhash, "mydbm", 0666)

The contents of the database are placed in the hash name (%myhash in the example above). Any values the hash had before executing dbmopen are lost. Any changes made to the hash while the Perl script is running are also made immediately to the database files.

To close an open database, use the dbmclose function.

     dbmclose (%myhash)

DBM does not support file locking.

Perl also provides the tie and untie functions as preferred replacements for dbmopen/dbmclose. Examples of both are given below.

Database Functions Reference
Here's a quick reference of the available database functions, in alphabetical order, along with code examples.

• dbmopen - open a dbm file

      dbmopen HASH, DBNAME, MASK     # mask provides file permissions
  
      Examples:
      dbmopen %myhash, "myfile", 0666
      

• dbmclose - close a dbm file

      dbmclose HASH
  
      Examples:
      dbmclose %myhash
      

• tie - bind a variable to an object class

      tie VARIABLE, CLASSNAME, LIST
  
      Examples:
      tie %myhash, "NDBM_File", "myfile", 1, 0666
      

• untie - break a tie binding to a variable

      untie VARIABLE
  
      Examples:
      untie %myhash
      

If you have any suggestions for additions to these tutorials, please let me know.