Thanks David.
Got another question that I have been trying to wrap my mind around. About
@argv. Now it says from I understand and read it access information from the
command prompt. How exactly does it work? Is it it's own database? Or am I
mistake, I know this may be a crazy question to ask.
Jason H. Owens
----- Forwarded Message ----
From: David Christensen <dpchr...@holgerdanske.com>
To: Slick <jho251...@yahoo.com>
Cc: beginners@perl.org
Sent: Tue, October 6, 2009 11:01:08 PM
Subject: Re: yet another question
Slick wrote:
> What do you guys do to practice? Do you practice one script over and over
> again? Do you read differnt scripts and figure out what is happening in each
> one? Do you think of ideas to do things, then make the script for that?
As they say:
"Necessity is the mother of invention."
I write Perl scripts because I need to get something done with my computers.
Monotonous, repetitive tasks are good candidates. For example, copying file
trees to a backup drive, making a tar / gzip archive of some files with a date/
time stamp in the archive name, and shutting down a network of computers in the
proper order. In fact, I've written and re-written those scripts dozens of
times (as my needs change/ expectations increase and as I learn more about
Perl). I then write one script to rule them all, so at the end of the day I
can launch one script, turn off the monitor, and go to bed. :-)
The steps are:
1. Get an idea -- e.g. "Hey, I bet I could write a Perl script to do this..."
(need).
2. Research in exact detail what it takes to make "this" happen -- e.g. data,
algorithms, sequence of steps, command syntax, reference information, etc.
(analysis).
3. Figure out how to accomplish "this" in Perl (design and implementation):
a. One approach is to break down the overall process into smaller steps
and solve them one at a time (procedural or structured programming). This is
the traditional approach, and how I learned to program.
b. Another approach is to model the system as objects that contain both
data and the operations that act upon that data (object-oriented programming).
This is a newer approach, and makes it easier to solve larger and more complex
problems.
I prefer books for learning and for reference, and found "Learning Perl",
"Programming Perl", and especially "The Perl Cookbook" to be invaluable when it
came time to start writing Perl code. I still refer to the later two often.
When you're ready for libraries (modules), object-oriented Perl, automated
testing, etc., get "Intermediate Perl".
Another aspect to #3 is learning to leverage all the "free" Perl scripts and
modules that are available on the Comprehensive Perl Archive Network:
http://www.cpan.org/
Data::Dumper is one such module. It is included in the base Perl distribution,
so you don't have to worry about downloading/ installing it. I find it
invaluable for debugging (the old-fashioned way, with "print" statements):
2009-10-06 20:56:25 dpchr...@p43400e ~
$ cat foo
#! /usr/bin/perl -w
use strict;
use warnings;
use Data::Dumper;
my $debug = 1;
print join(" ", __FILE__, __LINE__,
Data::Dumper->Dump([...@argv], [qw(*ARGV)])
) if $debug;
2009-10-06 20:56:29 dpchr...@p43400e ~
$ ./foo -x -y 'hello, world!' 123
./foo 8 @ARGV = (
'-x',
'-y',
'hello, world!',
'123'
);
HTH,
David
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