Monday, December 1, 2014

Sending Mail in Perl

Using MIME::Lite module

You could write your own email client using MIME:Lite perl module. You can download this module from MIME-Lite-3.01.tar.gz and install it on your either machine Windows or Linux/Unix. To install it follow the following simple steps:
$tar xvfz MIME-Lite-3.01.tar.gz
$cd MIME-Lite-3.01
$perl Makefile.PL
$make install
That's it and you will have MIME::Lite module installed on your machine. Now you are ready to send your email with simple scripts explained below.


Now following is a script which will take care of sending email to the given email ID:
use MIME::Lite;
$to = '';
$cc = '';
$from = '';
$subject = 'Test Email';
$message = 'This is test email sent by Perl Script';

$msg = MIME::Lite->new(
                 From     => $from,
                 To       => $to,
                 Cc       => $cc,
                 Subject  => $subject,
                 Data     => $message
print "Email Sent Successfully\n";


If you want to send HTML formatted email using sendmail then you simply need to add Content-type: text/html\n in the header part of the email. Following is the script which will take care of sending HTML formatted email:
use MIME::Lite;
$to = '';
$cc = '';
$from = '';
$subject = 'Test Email';
$message = '<h1>This is test email sent by Perl Script</h1>';

$msg = MIME::Lite->new(
                 From     => $from,
                 To       => $to,
                 Cc       => $cc,
                 Subject  => $subject,
                 Data     => $message
$msg->attr("content-type" => "text/html");         
print "Email Sent Successfully\n";


If you want to send an attachement then following script serve the purpose:
use MIME::Lite;
$to = '';
$cc = '';
$from = '';
$subject = 'Test Email';
$message = 'This is test email sent by Perl Script';

$msg = MIME::Lite->new(
                 From     => $from,
                 To       => $to,
                 Cc       => $cc,
                 Subject  => $subject,
                 Type     => 'multipart/mixed'
# Add your text message.
$msg->attach(Type         => 'text',
             Data         => $message
# Specify your file as attachement.
$msg->attach(Type        => 'image/gif',
             Path        => '/tmp/logo.gif',
             Filename    => 'logo.gif',
             Disposition => 'attachment'
print "Email Sent Successfully\n";
You can attache as many as files you like in your email using attach() method.

Using SMTP Server

If your machine is not running an email server then you can use any other email server available at remote location. But to use any other email server you will need to have an id, its password, URL etc. Once you have all the required information, you simple need to provide that information in send()method as follows:
$msg->send('smtp', "", AuthUser=>"id", AuthPass=>"password" );
You can contact your email server administrator to have above used information and if a user id and password is not already available then your administrator can create it in minutes.

Thursday, November 13, 2014

Isolating CPUs from the general scheduler in Linux.

It could be done using the kernel parameters:



<cpu number>,...,<cpu number>


<cpu number>-<cpu number>

(must be a positive range in ascending order) or a mixture

<cpu number>,...,<cpu number>-<cpu number>

This option can be used to specify one or more CPUs to isolate from the general SMP balancing and scheduling algorithms. You can move a process onto or off an "isolated" CPU via the CPU affinity syscalls or cpuset.

<cpu number> begins at 0 and the maximum value is "number of CPUs in system - 1".

This option is the preferred way to isolate CPUs. The alternative -- manually setting the CPU mask of all   tasks in the system -- can cause problems and suboptimal load balancer performance.

Taken from /usr/share/doc/kernel-doc-2.6.32/Documentation/kernel-parameters.txt

Boot parameters of the running kernel in Linux

Let's say I need to find out with what parameters did the kernel boot?

The following command will give you the answer:

cat /proc/cmdline

For example:

janeiros@harlie:~$ cat /proc/cmdline
BOOT_IMAGE=/vmlinuz-3.0.0-32-generic-pae root=/dev/mapper/harlie-root ro quiet

Tuesday, October 28, 2014

Endianness mnemotechnic

A long time ago I had a difficult time trying to remember the differences between Big Endian and Little Endian. I came out with this little trick to make it easier to remember: associate Low with 0.

In Big Endian, you store the most significant byte in the smallest address. In Little Endian, you store the least significant byte in the smallest address.

Monday, October 27, 2014

Guava Files class

Sometimes you are still in the Java 1.6 land and you just to want to read the entire file into a list. Guava can help you:
File file = new File("trades_3.txt");
List<String> lines = Files.readLines(file, Charset.defaultCharset());
The Files class doc.

Saturday, October 11, 2014

Foundation and Empire

  1. Part I: The General
    1. Search for Magicians
    2. The Magicians
    3. The Dead Hand
    4. The Emperor
    5. The War Begins
    6. The Favorite
    7. Bribery
    8. To Trantor
    9. On Trantor
    10. The War Ends
  2. Part II The Mule
    1. Bride and Groom
    2. Captain and Mayor
    3. Lieutenant and Clown
    4. The Mutant
    5. The Psychologist
    6. Conference
    7. The Visi-Sonor
    8. Fall of the Foundation
    9. Start of the Search
    10. Conspirator
    11. Interlude in Space
    12. Death on Neotrantor
    13. The Ruins of Trantor
    14. Convert
    15. Death of a Psychologist
    16. End of the Search

Friday, October 3, 2014


# List the rules with line numbers,
# the -n disables the DNS reverse lookup
iptables -n --list --line-numbers

# Block a specific IP
iptables -A INPUT -s -j DROP

# Allow SSH for a specific IP
iptables -A INPUT -s -p tcp -m tcp --dport 22 -j ACCEPT

# Delete a rule based on its number
iptables -D INPUT 8

# Insert rule before other certain one
# For example before line # 3
iptables -I INPUT 3 -s -p tcp -m tcp --dport 22 -j ACCEPT

Thursday, September 25, 2014

Java 8 installation on Fedora 14

  1. Download Java SDK/JRE from Oracle: (I selected the server version).
  2. Extract the files into /usr/local/java. (I created the java directory).
  3. Use the alternatives program to create the necessary links:
    • [root@Fedora-test ~]# alternatives --install /usr/bin/java java /usr/local/java/jdk1.8.0_20/bin/java 20000
    • Run the alternatives config command:
[root@Fedora-test ~]# alternatives --config java
Select the option for Java 8
    • Test it:
[root@Fedora-test ~]# java -version
java version "1.8.0_20"
Java(TM) SE Runtime Environment (build 1.8.0_20-b26)
Java HotSpot(TM) 64-Bit Server VM (build 25.20-b23, mixed mode)
The following link was useful:

Tuesday, September 23, 2014

Thursday, September 11, 2014

Dumping computer’s DMI (SMBIOS) in Linux


dmidecode -t

The SMBIOS specification defines the following DMI types:

       Type   Information
          0   BIOS
          1   System
          2   Baseboard
          3   Chassis
          4   Processor
          5   Memory Controller
          6   Memory Module
          7   Cache
          8   Port Connector
          9   System Slots
         10   On Board Devices
         11   OEM Strings
         12   System Configuration Options
         13   BIOS Language
         14   Group Associations
         15   System Event Log
         16   Physical Memory Array
         17   Memory Device
         18   32-bit Memory Error
         19   Memory Array Mapped Address
         20   Memory Device Mapped Address
         21   Built-in Pointing Device
         22   Portable Battery
         23   System Reset
         24   Hardware Security
         25   System Power Controls
         26   Voltage Probe
         27   Cooling Device
         28   Temperature Probe
         29   Electrical Current Probe
         30   Out-of-band Remote Access
         31   Boot Integrity Services
         32   System Boot
         33   64-bit Memory Error
         34   Management Device
         35   Management Device Component
         36   Management Device Threshold Data
         37   Memory Channel
         38   IPMI Device
         39   Power Supply
         40   Additional Information
         41   Onboard Devices Extended Information
         42   Management Controller Host Interface

Additionally, type 126 is used for disabled entries and type 127 is an end-of-table marker. Types 128 to 255 are for OEM-specific data.

Keywords can be used instead of type numbers with --type.  Each keyword is equivalent to a list of type numbers:

       Keyword     Types
       bios        0, 13
       system      1, 12, 15, 23, 32
       baseboard   2, 10, 41
       chassis     3
       processor   4
       memory      5, 6, 16, 17
       cache       7
       connector   8
       slot        9

Wednesday, August 13, 2014

Excel Regular Expressions

Sub RegEx_Tester()
    Dim objRegExp_1 As Object
    Dim regExp_Matches As Object
    Dim strToSearch As String
    Set objRegExp_1 = CreateObject("vbscript.regexp")
    objRegExp_1.Global = True
    objRegExp_1.IgnoreCase = True
    objRegExp_1.Pattern = "[a-z,A-Z]*@[a-z,A-Z]*.com"
    strToSearch = ""
    Set regExp_Matches = objRegExp_1.Execute(strToSearch)
    If regExp_Matches.Count = 1 Then
        MsgBox ("This string is a valid email address.")
    End If
End Sub

Thursday, July 10, 2014

flock - Manage locks from shell scripts

Only one running instance of a script:

flock -n /var/lock/lock_file.lock

Thursday, May 29, 2014


I know what the caged bird feels, alas!
When the sun is bright on the upland slopes;
When the wind stirs soft through the springing grass,
And the river flows like a stream of glass;
When the first bird sings and the first bud opes,
And the faint perfume from its chalice steals—
I know what the caged bird feels!
I know why the caged bird beats his wing
Till its blood is red on the cruel bars;
For he must fly back to his perch and cling
When he fain would be on the bough a-swing;
And a pain still throbs in the old, old scars
And they pulse again with a keener sting—
I know why he beats his wing!
I know why the caged bird sings, ah me,
When his wing is bruised and his bosom sore,—
When he beats his bars and he would be free;
It is not a carol of joy or glee,
But a prayer that he sends from his heart's deep core,
But a plea, that upward to Heaven he flings—
I know why the caged bird sings!

Paul Laurence Dunbar

Wednesday, April 30, 2014

systemd-analyze - Analyze system boot-up performance

systemd-analyze may be used to determine system boot-up performance of the current boot.

systemd-analyze blame prints a list of all running units, ordered by the time they took to initialize.

SysVinit to Systemd Cheatsheet

Wednesday, January 15, 2014

Fedora Full List of Kernel Options

The full list of kernel options is in the file /usr/share/doc/kernel-doc-<version>/Documentation/kernel-parameters.txt, which is installed with the kernel-doc package.

Taken from:

Thursday, January 2, 2014

2014 Federal Holidays

2014 Holiday Schedule
Wednesday, January 1New Year’s Day
Monday, January 20Birthday of Martin Luther King, Jr.
Monday, February 17 *Washington’s Birthday
Monday, May 26Memorial Day
Friday, July 4Independence Day
Monday, September 1Labor Day
Monday, October 13Columbus Day
Tuesday, November 11Veterans Day
Thursday, November 27Thanksgiving Day
Thursday, December 25Christmas Day
*This holiday is designated as "Washington’s Birthday" in section 6103(a) of title 5 of the United States Code, which is the law that specifies holidays for Federal employees. Though other institutions such as state and local governments and private businesses may use other names, it is our policy to always refer to holidays by the names designated in the law.