February 2012
Intermediate to advanced
1184 pages
37h 17m
English
Content preview from Programming Perl, 4th Editiondbmopen
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dbmopen 
dbmopenHASH,DBNAME,MODE
This binds a DBM file to a hash (that is, an associative
array). (A DBM consists of a set of C library routines that allow random
access to records via a hashing algorithm.)
HASH is the name of the hash (including the
%). DBNAME
is the name of the database (without any .dir or .pag extension). If the database does not
exist and a valid MODE is specified, the
database is created with the protection specified by
MODE, as modified by the umask. To prevent
creation of the database if it doesn’t exist, you may specify a
MODE of undef, and the function will return false if
it can’t find an existing database. Values assigned to the hash before
the dbmopen are not
accessible.
The dbmopen function is really
just a call to tie with the proper
arguments, provided for backward compatibility with ancient versions of
Perl. The return value from dbmopen
is the same as it would be if you had called tie yourself: the tied object on success, or
false on failure. You can control which DBM library you use by using the
tie interface directly or by loading
the appropriate module before you call dbmopen. Here’s an example that works on some
systems for versions of DB_File similar to the version in your Netscape browser:
use DB_File; dbmopen(%NS_Hist, "$ENV{HOME}/.netscape/history.dat", ...Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.