tie function.]
This binds a dbm, ndbm, sdbm, gdbm, or Berkeley
DB file to a hash.
HASH is the name of the hash. (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 supports only 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.
If you don't have write access to the
DBM file, you can only read hash variables, not set
them. If you want to test whether you can write, either use file tests or
try setting a dummy hash 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:
# print out history file offsets
dbmopen(%HIST,'/usr/lib/news/history',0666);
while (($key,$val) = each %HIST) {
print $key, ' = ', unpack('L',$val), "\n";
}
dbmclose(%HIST);
See also the AnyDBM_File manpage for a more general description of the pros and cons of the various dbm approaches, as well as the DB_File manpage for a particularly rich implementation.