Loading from a module in another file

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Hashes example from a Well House Consultants training course
More on Hashes [link]

This example is described in the following article(s):
• Fresh Perl Teaching Examples - part 2 of 3 - [link]

Source code: acc_0 Module: P211

=head1 A practical example - Perl analysing and reporting on a log file

This example was written towards the end of a five day
Introduction to Programming in Perl course - and it shows
the use of lists, hashes, and the loading of a perl module
from another file.

Some of the techniques used aren't necessarily best practise
as this was a live example, and there are some things shown
for clarity rather than efficiency - and clarity for newcomers
to Perl code who often find two simpler statements easier than
one more complex one. Some variable names were chosen to
show flexibility in variable naming, rather than for ease of
later maintainance.

=cut

use ford;

open (FH,"access_log.xyz") or die;

# Subroutine henry is within the ford module ...
# it reads a web log file into a global hash called counter
# such that the keys are the visiting client host names,
# and the values are the number of visits from each client.

henry();

sub byvalue {
        $counter{$b} - $counter{$a};
        }

@visitors = keys(%counter);
@visitors = sort byvalue (@visitors);

# Sample outputs - a list of all the visiting hosts

print "Seen from @visitors\n";

# All the visiting hosts, with the number of visits from each

foreach $hv (@visitors) {
        printf "%12s %5d\n",$hv,$counter{$hv};
        }

# Everything about the top ten visitors ...

for ($k=0; $k<10; $k++) {
        $num = $counter{$visitors[$k]} ;
        print "$k $visitors[$k] $num\n";
        }

# ... and a summary of the rest of the visitors

for ($k=10; $k<@visitors; $k++) {
        print "$visitors[$k] ";
        }
print "\n";

=head2 Note

Note that list slices ( @visitors[0..9] and @visitors[10..$#visitors])
would make the final two output loops cleaner, at the expense of using
a somewhat more sophisticated structure for coding newcomers

=cut

Learn about this subject

This module and example are covered on the following public courses:
* Perl Programming
* Perl bootcamp
* Learning to program in Perl
* Perl Programming
Also available on on site courses for larger groups

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Other Examples

This example comes from our "Hashes" training module. You'll find a description of the topic and some other closely related examples on the "Hashes" module index page.

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Further Examples

acc_0 - Loading from a module in another file

access_log.xyz - Log file used in many Well House exercises

account - Sample - extracting statistics from an access log file

acl - Sample answer - web_c2, page 152

aco_1 - Access log - listing hosts via a hash

bankout - initialising a hash

blx.pl - Use of hashes in Perl / CGI

cbdemo - How sort callbacks work

channel - Ferries to France - data file

env2 - ENV module to import variables as globals