This binds a dbm(3), ndbm(3), sdbm(3), gdbm(), or Berkeley DB file to an associative array. ASSOC is the name of the associative array. (Unlike normal open, the first argument is NOT a filehandle, even though it looks like one). DBNAME is the name of the database (without the .dir or .pag extension if any). If the database does not exist, it is created with protection specified by MODE (as modified by the umask() ). If your system only supports the older DBM functions, you may perform only one dbmopen() in your program. In older versions of Perl, if your system had neither DBM nor ndbm, calling dbmopen() produced a fatal error; it now falls back to sdbm(3).
If you don't have write access to the DBM file, you can only read associative array variables, not set them. If you want to test whether you can write, either use file tests or try setting a dummy array entry inside an eval() , which will trap the error.
Note that functions such as keys() and values() may return huge array values when used on large DBM files. You may prefer to use the each() function to iterate over large DBM files. Example:
See also AnyDBM_File for a more general description of the pros and cons of the various dbm apparoches, as well as DB_File for a particularly rich implementation.