Embedding Perl in HTML with Mason

This book is available for free @_ http://www.masonbook.com/book/

Perl Inheritance Simplified

http://perl.active-venture.com/pod/perltoot-inheritance.html

Perl Special Literals list

__FILE__ = represent the current filename
__LINE__ = line number
__PACKAGE__ package name

If there is no current package (due to an empty package; directive),
__PACKAGE__ is the undefined value.

The two control characters ^D and ^Z, and the tokens __END__ and __DATA__ may be used to indicate the logical end of the script before the actual end of file. Any following text is ignored.

Text after __DATA__ may be read via the filehandle PACKNAME::DATA, where PACKNAME is the package that was current when the __DATA__ token was encountered. The filehandle is left open pointing to the contents after __DATA__. It is the program's responsibility to close DATA when it is done reading from it. For compatibility with older scripts written before __DATA__ was introduced, __END__ behaves like __DATA__ in the top level script (but not in files loaded with require or do) and leaves the remaining contents of the file accessible via main::DATA.

See SelfLoader for more description of __DATA__, and an example of its use. Note that you cannot read from the DATA filehandle in a BEGIN block: the BEGIN block is executed as soon as it is seen (during compilation), at which point the corresponding __DATA__ (or __END__) token has not yet been seen

How to determine Total memory (Total RAM, Used RAM, Free RAM) on Unix/Linux

'free' tool prints pretty much everything.

total used free shared buffers cached
Mem: 514592 274136 240456 0 20228 134104
-/+ buffers/cache: 119804 394788
Swap: 1052216 0 1052216

or

cat /etc/meminfo - has all the information.

How to find out which process is listening upon a port

For standard processes, Services names can be seen in /etc/services files associated with port numbers. This is pretty much standard TCP/IP.

For non-standard user defined services,

lsof -i :port_number

For example:

So to see which process is listening upon port 80 we can run:

root@mystery:~# lsof -i :80
This gives us the following output:

COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
apache2 10437 root 3u IPv6 22890556 TCP *:www (LISTEN)
apache2 10438 www-data 3u IPv6 22890556 TCP *:www (LISTEN)
apache2 10439 www-data 3u IPv6 22890556 TCP *:www (LISTEN)
apache2 10440 www-data 3u IPv6 22890556 TCP *:www (LISTEN)
apache2 10441 www-data 3u IPv6 22890556 TCP *:www (LISTEN)
apache2 10442 www-data 3u IPv6 22890556 TCP *:www (LISTEN)
apache2 25966 www-data 3u IPv6 22890556 TCP *:www (LISTEN)
apache2 25968 www-data 3u IPv6 22890556 TCP *:www (LISTEN)

Best practices for a high performance Perl program

http://makepp.sourceforge.net/1.50/perl_performance.html

Validating data types in PERL

Since perl data types are very typeless and depends upon where they are used. There are some situations, when this design is awkward.

To validate data types,

Data::Types module can be installed and used.

However if you dont want to install, here are few quickies:

- To Check

% An Integer, Use regex /^[+-]?\d+$/ and ofcourse, not matched ones are non-intger
% A Decimal, /^[+-]?(?:\d+(?:\.\d*)?|\.\d+)$/
% Whole number, /^\d+$/
% Float number, /^([+-]?)(?=\d|\.\d)\d*(\.\d*)?([Ee]([+-]?\d+))?$/
%