Need some help with my script

John_L · #1 (**permalink**) 05-15-2008, 05:36 PM

Basic XML parser. I noted an "EMPTY???" comment beside the area which doesn't print anything. It's strange because the variables do get filled properly...anyone have any ideas?

Code:

#!/usr/bin/perl -w 

my $title = ""; #title
my $link  = ""; #link
my $description = ""; #description
my $item_found = 0; # <item> element within the xml file

print "<html>\n";
print "\n\t<body>\n";


#read xml file from standard input
while( $line = <stdin> )
{
	
	#remove white space
	chomp( $line );
			
	if( $item_found == 0 )
	{	
		$start = index( $line, "item" ); #find an item tag
		
		if( $start != -1 )
		{
			$item_found = 1; #beginning of item
		}
	}
	
	if( $item_found == 1 )
	{

		#parse data that we want
				
		$title = &process_element( $line, "title" ); 
		$link = &process_element( $line, "link" );
		$description = &process_element( $line, "description" );
				
		#look for the end of item tag
		$end = index( $line, "/item" );
			
		if( end != -1 )
		{
			
			#print the gathered information to the html file			
			if( length( $title ) != 0 || length( $link ) != 0 || length( $description ) != 0 )
			{
				print "\n\t\t<p> \n\t \t\t<a href= \"$link\"> $title </a> \n\t\t\t $description \n\t\t</p>\n\n" ; #EMPTY????
			}
			
			#clear stored information
			$title = "";
			$link = "";
			$description = "";
			
			$chann_found = 0; #end of channel
			$item_found = 0; #end of item
		}
		
	}
	
	

}

#$_[0] = line, $_[1] = tag
sub process_element
{	
	#my ( $start, $end, $length );		#private local variables 
	#my $information = "";
	
	#Grab the string between these tags
	$start = index( $_[0], "$_[1]" );	#assume this is how a beginning tag will always look
	$end = rindex( $_[0], "</" );		#this is how an ending tag will always look
			
	if( $start != -1 )
	{
		$start = index( $_[0], ">" ) + 1; #advance start to the end of the tag
		$end = rindex( $_[0], "<" ); #advance start to the beginning of the closing tag
			
		$length = length( $_[0] );
			
		#end tag wasn't on the same line
		if( $end == -1 )
		{
			$end = $length;
		}
			
		$length = $end - $start; #the length of the substring
		
		$information = substr( $_[0], $start, $length );
		
		#replace encoded characters if any exist
		$information =~ s/&lt;/</;
		$information =~ s/&gt;/>/;
		$information =~ s/&amp;/&/;
					
		return $information
		
	}
}

print "\n\t</body>\n";
print "\n</html>\n\n";

John_L · #2 (**permalink**) 05-15-2008, 06:09 PM

never mind...i know what was wrong.

**v0id** · #3 (**permalink**) 05-15-2008, 11:51 PM

Can you explain what was wrong? Other users might have the same problem as you had.

John_L · #4 (**permalink**) 05-16-2008, 10:26 AM

no problem. In subroutines a return value is not necessary, but you can include one. It doesn't follow the same structure as high level language though, notice how mine is inside an if statement, so it could in fact never execute, leaving my subroutine without a return value (not allowed in many languages). That was the issue, on certain cases the variables assigned to the subroutine value returned ended up either equaling nothing or whatever may be equivalent to void. So my variables would equal the correct value, but following another execution of the subroutine given a case where the return statement wasn't executed, they were overridden. I hope that makes sense....and is understandable. I just threw in a "error check" if statement to correct the problem.

jmcallister · #5 (**permalink**) 05-17-2008, 04:21 PM

Thank you for sharing the issue with us this actually helped me with a build perl script that i have been having problems with.

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