Perl: June 2008 Archives

I wanted a tool to show up network i/o statistics - just like iostat does for disk access. I used Sun::Solaris::Kstat in Perl, available in Solaris 10 package SUNWperl584core.

The only paramter my script accepts for now is the time delay between two measurements.

Example:

-bash-3.00$ knetstat 2
            network i/o statistics
       r/s        t/s        kr/s        kt/s  interface
            network i/o statistics
       r/s        t/s        kr/s        kt/s  interface
      1086       1916       91.75     2400.10  e1000g0
      45.5       48.5        6.78        8.51  e1000g1
            network i/o statistics
       r/s        t/s        kr/s        kt/s  interface
    1129.5       1921       99.30     2396.48  e1000g0
      17.5         18        2.46        2.59  e1000g1
            network i/o statistics
       r/s        t/s        kr/s        kt/s  interface
     706.5       1063       79.56     1199.68  e1000g0
        16         18        2.43        2.63  e1000g1

You may download the tiny perl script here.

On  the other day, I wanted to access Postfix dbm: and hash:-tables, created by postmap, from Perl. I am setting up a greylisting system and my whitelist should be a postfix table, so I won't have to use another database format.

I used this as a test table:

test1   myentry
test2   yourentry
test3   funny

I saved it as "testmap". After that, I used:

postmap testmap

Result:

-rw-r--r-- 1 pascal users    42 2008-06-16 10:14 testmap
-rw-r--r-- 1 pascal users 12288 2008-06-16 10:14 testmap.db

You may access this hash-type postfix-db just by using DB_File:

#!/usr/bin/perl

use Fcntl;
use DB_File;

my %tab;
my $null=chr(0);

tie %tab,'DB_File','testmap.db',O_RDONLY,0400,$DB_HASH;

# Sample query
my $key='test2';

my $value=$tab{$key.$null};
chop $value;  # chop null byte

print $key." = ".$value."\n";

Result:

test2 = yourentry

As you can see, the key must be terminated by a null byte, and the result itself is also null-terminated.

In case you use the dbm:-Format in postmap:

-rw-r--r--   1 root     root          42 Jun 16 11:30 testmap
-rw-r--r--   1 root     root           0 Jun 16 11:30 testmap.dir
-rw-r--r--   1 root     root        1024 Jun 16 11:30 testmap.pag

In Perl, just use NDBM_File instead and use the filename without .dir or .pag:

#!/usr/bin/perl

use Fcntl;
use NDBM_File;

my %tab;
my $null=chr(0);

tie %tab,'NDBM_File','testmap',O_RDONLY,0400;

# Sample query
my $key='test2';

my $value=$tab{$key.$null};
chop $value;  # chop null byte

print $key." = ".$value."\n";

The Keys and values are also null-terminated in this case.

Result is the same as with our hash:-Postfix-Table:

test2 = yourentry