| |||||||||||
| |||||||||||
Getting multiple results from a single data traversal
Programming Algorithms example from a Well House Consultants training course
More on Programming Algorithms [link]
Source code: scat Module: Q110
=head1 There are many occasions when you want to write a program that scans through a big file of data and produces a variety of reports from it - certain types of data filtered in certain ways. A problem is that if you filter the data as you read it for the first report, you'll then have to read it again for the second report if you don't want your outputs mixed up. Fortunately, there's an easy solution. As you filter the data, instead of outputting results, you make up text strings in variables in memory that contain each of the reports ... then, when you've completed scanning the input file, you can simply dump out each of the variable strings in turn. Here's an example using this technique - it actually outputs one report as it's run (a good thing as you can see progress if you're running it interactively), and the others when the data file handling has been completed. =cut # 204.236.235.245 - - [20/Jun/2010:03:30:26 +0100] # "GET /resources/ex.php4?item=y105/sysdemo.py HTTP/1.0" 200 20485 # "-" "ia_archiver (+http://www.alexa.com/site/help/webmasters; crawler@alexa.com)" $fname = "ac_20100624"; # Extra demo - eliminate empty or non-existant file! unless (-s $fname) { die "Nutting Dere!\n"; } # This form of open only works with Perl 5.6 and later open (FH,"<","$fname") or die ("[1005] Can't open $fname - $!\n"); while ($lyne = <FH>) { if ($lyne =~ m%GET /resources/P207\.html%) { print $lyne; } if ($lyne =~ m%GET /resources/P208\.html%) { $p208 .= $lyne; } if ($lyne =~ m%GET /resources/ex\.php4\?item=(\S+)%) { $samples .= "$1\n"; } } print $p208; print $samples; Learn about this subject
This module and example are covered on our public Learning to program in Perl course. If you have a group of
three or more trainees who need to learn the subject, we can also arrange a
private or on site course for you.
Books covering this topic
Yes. We have over 700 books in our library. Books
covering all the subjects we teach are listed here and when you've selected a
relevant book we'll link you on to Amazon to order.
Other Examples
This example comes from our "Programming Algorithms" training module. You'll find a description of the topic and some
other closely related examples on the "Programming Algorithms" module index page.
Full description of the source code
You can learn more about this example on the training courses listed on this page,
on which you'll be given a full set of training notes.
Many other training modules are available for download (for limited use) from our download centre under an Open Training Notes License. Other resources
• Our Solutions centre provides a number of longer technical articles.
• Our Opentalk forum archive provides a question and answer centre. • The Horse's mouth provides a daily tip or thought. • Further resources are available via the resources centre. • All of these resources can be searched through through our search engine • And there's a global index here. Purpose of this website
This is a sample program, class demonstration or answer from a
training course. It's main purpose
is to provide an after-course service to customers who have attended our
public private or
on site courses, but the examples are made
generally available under conditions described below.
Web site author
Conditions of use
Past attendees on our training courses are welcome to use individual
examples in the course of their programming, but must check
the examples they use to ensure that they are suitable for their
job. Remember that some of our examples show you how not to do
things - check in your notes. Well House Consultants take no responsibility
for the suitability of these example programs to customer's needs.
This program is copyright Well House Consultants Ltd. You are forbidden from using it for running your own training courses without our prior written permission. See our page on courseware provision for more details. Any of our images within this code may NOT be reused on a public URL without our prior permission. For Bona Fide personal use, we will often grant you permission provided that you provide a link back. Commercial use on a website will incur a license fee for each image used - details on request. |
| ||||||||||
PH: 01144 1225 708225 • EMAIL: info@wellho.net • WEB: http://www.wellho.net • SKYPE: wellho PAGE: http://www.wellho.net/resources/ex.php • PAGE BUILT: Sun Oct 11 14:50:09 2020 • BUILD SYSTEM: JelliaJamb |