#!/usr/bin/perl

###########################################################################
# This is an example Perl script that doesn't do that much.  It is mostly an 
# example of Perl syntax.  The last part of the example is a basic web 
# server log analysis program.
###########################################################################


###########################################################################
# Types of variables
###########################################################################
#
# Scalar variables always start with a "$" whether they are on the left or
# right hand side of an expression.  This differs from bourne, korn, 
# and C-shell scripts.
$logDir="/var/log/httpd";
$logFile="$logDir/access_log";

#
# arrays 
# Arrays can be referenced two ways, in an array "context", or in a 
# scalar "context".  In an array context, the array name starts with 
# a %.  When referenced with a $, the value of the array is evaluated
# as a scalar value.  Arrays are referenced as scalars when you are 
# accessing a single element of the array by its subscript.   When the
# name of the array is referenced with an $ and no subscript, the 
# value of the expression is the length of the array.
%months=("", "January", "February", "March", "April", "May", "June", 
	"July", "August", "September", "October", "November", "December");
$mar=$months[3];
$monthCount=$months -1;

#
# Hashes or associative arrays
# One of the most useful innovations in Perl.  An associative array
# is like an array where the index is a string rather than an integer.
# When referenced with a @, the variable is an array.  When used with 
# a $ and a subscript, you get the value of the array element.  Without
# the subscript, you get the 
%namesAndNicknames ("Andrew", "Andy", "William", "Bill", "James", Jim");
$nickname=$namesAndNicknames {"Andrew");
$namesAndNicknames {"William"} = "Billy Bob";
#
# Get a list of hash keys
@names=keys (%namesAndNicknames);
#
# Get a list of the values in the hash
@values=values (%namesAndNicknames);

###########################################################################
# A subroutine definition and call
###########################################################################
sub isEqual {
my ($parm1, $parm2) = @_;
if ( $parm1 eq $parm2) {
	return 1;
} else {
	return 0;
};
};

$rc=isEqual ("abc", "def");
 

###########################################################################
# Simple control structures
###########################################################################
if ( $nickname eq "Billy Bob" ) {
	nascarfan("true");
} elsif ( $nickname eq "Nigel" ) {
	f1fan("true");
};

$length = @names;
for ($ii=0; $ii < $length; $ii++) {
	print ("$names [$ii] aka $namesAndNicknames{$names [$ii]} \n");
};

foreach $name (@names) {
	printf ("%s aka %s \n", 
		$name, $namesAndNicknames {$name});
};

#
# open a file for output, read from standard in, and write it to the outfile.
open (OUTFILE, "> /var/tmp/junk");
while ( $_ = <>) {
	print (OUTFILE "$_");
};

#
# The first parm in the open command is the file handle name, File handles
# have odd syntax... they do not have any special character in front of them
# such as $, %, or &.  
open (LOG,"<$logFile") || die "error: can not open $LOG";
#
# split the lines of the log file.  Ex.
# host.someisp.net - someuserid [01/Jan/1998:08:30:15 -0500] "GET /~welter/index.html HTTP/1.1" 304 -
while (<LOG>) {
	($host,$junk,$userid,$date,$time,$request,$url,$protocol,$junk2) = 
		split (/\s+/);
	if (($url =~ /welter/) && !($url =~ /jpg/)) {
		$urls {"$url"} ++;
		$hosts {"$host"} ++;
		$dates {"$date"} ++; 
	};
};

print "URL Requests by host.\n";
while (($key ,$count) = each %hosts) {
	print "$count\t$key\n";
};

print "\nURL Requests by URL.\n";
while (($key ,$count) = each %urls) {
	print "$count\t$key\n";
};

# sort some hash by value
@sorted = sort { $hash{$a} cmp $hash{$b} } keys %hash; 
for $key (@sorted) {
	print $hash{$key}\n;
done