PERL Modules - DBM and Perl

Author

DBM and Perl

Raj

2006-10-17, 7:56 am

Hi,

I have tried to understand the docs to use NDBM_File, but haven't quite
understood it. I have used the following to connect to a DBM file:

#!/usr/bin/perl -w

use strict;
use NDBM_File;

my %bills;
my ($dbh, $key, $val);

$dbh = tie(%bills, 'NDBM_File', 'bills_generated', 1, 0);
while (($key, $val) = each %bills) {
print $key, ' = ', unpack('L', $val), "\n";
}
untie(%bills);
exit 0;

But I don't know how to store something in the file. The documentation
suggests that I have to create my own class, but I don't understand this
requirement. Is there not a default way to do this?

Thanks in advance.

Regards,
--
Raj Kothary :: one|concept

Mumia W. (reading news)

2006-10-17, 6:56 pm

On 10/17/2006 08:11 AM, Raj wrote:
> Hi,
>
> I have tried to understand the docs to use NDBM_File, but haven't quite
> understood it. I have used the following to connect to a DBM file:
>
> #!/usr/bin/perl -w
>
> use strict;
> use NDBM_File;
>
> my %bills;
> my ($dbh, $key, $val);
>
> $dbh = tie(%bills, 'NDBM_File', 'bills_generated', 1, 0);
> while (($key, $val) = each %bills) {
> print $key, ' = ', unpack('L', $val), "\n";
> }
> untie(%bills);
> exit 0;
>
> But I don't know how to store something in the file. The documentation
> suggests that I have to create my own class, but I don't understand this
> requirement. Is there not a default way to do this?
>
> Thanks in advance.
>
> Regards,

Write to the hash %bills to store something in the file.

--
paduille.4060.mumia.w@earthlink.net

John W. Krahn

2006-10-17, 6:56 pm

Raj wrote:
>
> I have tried to understand the docs to use NDBM_File, but haven't quite
> understood it. I have used the following to connect to a DBM file:
>
> #!/usr/bin/perl -w
>
> use strict;
> use NDBM_File;
>
> my %bills;
> my ($dbh, $key, $val);
>
> $dbh = tie(%bills, 'NDBM_File', 'bills_generated', 1, 0);

You shouldn't use "magic numbers": what do 1 and 0 stand for? You should
*ALWAYS* verify that the file opened correctly.

use Fcntl;
my $dbh = tie my %bills, 'NDBM_File', 'bills_generated', O_RDWR
or die "Cannot open 'bills_generated' $!";

> while (($key, $val) = each %bills) {

You don't need those variables in file scope:

while ( my ( $key, $val ) = each %bills ) {

> print $key, ' = ', unpack('L', $val), "\n";
> }
> untie(%bills);
> exit 0;
>
> But I don't know how to store something in the file.

(Before you untie the hash.)

$bills{ 'key' } = pack 'L', 12345;

John
--
Perl isn't a toolbox, but a small machine shop where you can special-order
certain sorts of tools at low cost and in short order. -- Larry Wall

Raj

2006-10-18, 3:57 am

"John W. Krahn" <someone@example.com> wrote in message
news:MN6Zg.27457$P7.995@edtnps89...
> Raj wrote:
>
> You shouldn't use "magic numbers": what do 1 and 0 stand for? You should
> *ALWAYS* verify that the file opened correctly.
>
> use Fcntl;
> my $dbh = tie my %bills, 'NDBM_File', 'bills_generated', O_RDWR
> or die "Cannot open 'bills_generated' $!";
>
>
>
> You don't need those variables in file scope:
>
> while ( my ( $key, $val ) = each %bills ) {
>
>
>
> (Before you untie the hash.)
>
> $bills{ 'key' } = pack 'L', 12345;

Thank you and Mumia for your help...what I had read made it sound more
difficult, or maybe my interpretation did!

Do you have to pack the assignment to the hash?

Thanks
Raj

>
>
>
> John
> --
> Perl isn't a toolbox, but a small machine shop where you can special-order
> certain sorts of tools at low cost and in short order. -- Larry Wall

Raj

2006-10-18, 7:56 am

"Raj" <raj.kothary@thus.net> wrote in message
news:eh4s5f$jsj$1$8302bc10@news.demon.co.uk...
> "John W. Krahn" <someone@example.com> wrote in message
> news:MN6Zg.27457$P7.995@edtnps89...
>
> Thank you and Mumia for your help...what I had read made it sound more
> difficult, or maybe my interpretation did!
>
> Do you have to pack the assignment to the hash?

Sorry, please ignore the above...silly question. Thanks for your help.

Regards,
Raj

> Thanks
> Raj
>
>
>

Sponsored Links