dbmopen - create binding on a tied dbm file
dbmopen HASH,DBNAME,MODE
[This function has been superseded by the tie() function.]
This binds a
dbm(3),
ndbm(3),
sdbm(3),
gdbm(3), 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(3).
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 lists 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.
If rather than formatting bugs, you encounter substantive content errors in these documents, such as mistakes in the explanations or code, please use the perlbug utility included with the Perl distribution.