%ARRAYNAME parameter is a Perl hash. (If this hash already has values, the values are discarded.) This hash becomes connected to the DBM database called dbmfilename, usually stored on disk as a pair of files called dbmfilename.dir and dbmfilename.pag.
$mode parameter is a number that controls the permission bits of the pair of files if the files need to be created. The number is typically specified in octal format; the frequently used value of
0666 provides read-write access to the database. If the files already exist, this parameter has no effect. For example:
dbmopen(%FRED, "mydatabase", 0666); # open %FRED onto mydatabase
This invocation associates the hash
%FRED with the disk files mydatabase.dir and mydatabase.pag in the current directory. If the files don't already exist, they are created with read/write attributes.
The return value from
dbmopen is true if the database could be opened or created, and false otherwise, just like an
open invocation. If you don't want the files created, use a
$mode value of
undef. For example:
dbmopen(%A,"c:/temp/xx",undef) || die "cannot open DBM c:/temp/xx";
In this case, if the files c:\temp\xx.dir and c:\temp\xx.pag cannot be opened, the
dbmopen call returns false, rather than attempting to create the files.
The DBM array stays open throughout the program. When the program terminates, the association is terminated. You can also break the association in a manner similar to closing a filehandle, by using the
dbmclose returns false if something goes wrong.