Implement the Delete a Forum option in default.pl. Selecting this option should display the initial screen, but with each forum name followed by a hyperlink to a script named del- Forum.pl. Your script should remove the given forum from forums.xml and delete the underlying XML document. [Hint: Look at the getElementsByTagName and removeChild methods described in the XML::DOM documentation.]

Question

What will be an ideal response?

Answer 1

```
1 #!/usr/bin/perl
2 # default.pl
3 # Default page for XML forums
4
5use warnings;
6 use strict;
7 use CGI qw( :standard );
8 use XML::Parser;
9 use Fcntl qw( :flock );
10
11 my ( $parser, $prefix, @files, @forums, @items );
12
13 open XML, "../htdocs/XML/forums.xml" or die "Could not open: $!";
14 flock XML, LOCK_UN;
15 flock XML, LOCK_SH;
16 $parser = new XML::Parser( Handlers => { Start => \&startTag,
17 Char => \&text } );
18 $parser->parse( \*XML );
19
20 print header( -expires => "-1d", -cache_control => "no-cache",
21 -pragma => "no-cache"),
22 start_html( -title => "Deitel Message Forums",
23 -style => { -src => "../XML/site.css" } );
24
25 print h1( "Deitel Message Forums" );
261 #!/usr/bin/perl
2 # default.pl
3 # Default page for XML forums
45
use warnings;
6 use strict;
7 use CGI qw( :standard );
8 use XML::Parser;
9 use Fcntl qw( :flock );
10
11 my ( $parser, $prefix, @files, @forums, @items );
12
13 open XML, "../htdocs/XML/forums.xml" or die "Could not open: $!";
14 flock XML, LOCK_UN;
15 flock XML, LOCK_SH;
16 $parser = new XML::Parser( Handlers => { Start => \&startTag,
17 Char => \&text } );
18 $parser->parse( \*XML );
19
20 print header( -expires => "-1d", -cache_control => "no-cache",
21 -pragma => "no-cache"),
22 start_html( -title => "Deitel Message Forums",
23 -style => { -src => "../XML/site.css" } );
24
25 print h1( "Deitel Message Forums" );
26
27 if ( $ENV{ "HTTP_USER_AGENT" } =~ /MSIE/i ) {
28 $prefix = "../XML/";
29 }
30 else {
31 $prefix = "forum.pl?file=";
32 }
33
34 @items = map { a( { -href => "$prefix$files[ $_ ]" }, $forums[$_] ) }
35 ( 0 .. $#files );
36
37 if ( param( "modify" ) )
38 {
39 my $action = param( "modify" ) eq "modify" ? "mod" : "del";
40 my $link = param( "modify" ) eq "modify" ? "Modify" : "Delete";
41
42 @items = map { $items[ $_ ] . " " .
43 a( { -href => "$action" . "Forum.pl?file=$files
44 [$_ ]",
45 -class => "modify" },
46 "[ $link ]" ) }
47 ( 0 .. $#files );
48 }
49
50 print p( strong( "Avaliable Forums" ), ul( li( \@items ) ) );
51
52 @items = ( a( { -href => "addForum.pl" }, "Add a Forum" ),
53 a( { -href => "default.pl?modify=modify" }, "Modify a
54 Forum" ),
55 a( { -href => "default.pl?modify=delete" }, "Delete a
56 Forum" ),
57 a( { -href => "default.pl" }, "Home" ) );
58
59 print p( strong( "Forum Management" ), ul( li( \@items ) ) ),
60 end_html;
61 close XML;
62
63 sub startTag
64 {
65 my ( $expat, $element, %attributes ) = @_;
66 push( @files, $attributes{ "filename" } ) if $element eq "forum";
67 }
68
69 sub text
70 {
71 my ( $expat, $string ) = @_;
72 push( @forums, $string ) if $expat->in_element( "name" );
73 }
```
```
1 #!perl
2 # Sol. 17.4: delForum.pl
34use warnings;
5 use strict;
6 use CGI qw( :standard );
7 use XML::DOM;
8 use Fcntl qw( :flock :DEFAULT );
9 use CGI::Carp qw( fatalsToBrowser );
10
11 if ( param ) {
12 my ( $parser, $document, $forums, $forum, $name, $erase );
13
14 my $file = "forums.xml";
15
16 open XML, "+< ../htdocs/XML/$file" or die "Could not open: $!";
17 flock XML, LOCK_EX;
18
19 $parser = new XML::DOM::Parser;
20 $document = $parser->parse( \*XML );
21 $forums = $document->getDocumentElement;
22
23 foreach $forum ( $forums->getElementsByTagName( "forum" ) ) {
24 $file = $forum->getAttribute( "filename" );
25 if ( $file eq param( "file" ) ) {
26 $file =~ /^\w+\.xml$/ or die "Not a valid file: $!";
27 unlink( "../htdocs/XML/$file" ) or die
28 "Could not unlink: $!";
29 $forums->removeChild( $forum );
30 }
31 }
32
33 seek XML, 0, 0;
34 truncate XML, 0;
35 $document->print( \*XML );
36 close XML;
37 print redirect( "default.pl" );
38
39 }
40 else {
41 print redirect( "error.html" );
42 }
```
```
1 #!perl
2 # Sol. 17.4: delForum.pl
34use warnings;
5 use strict;
6 use CGI qw( :standard );
7 use XML::DOM;
8 use Fcntl qw( :flock :DEFAULT );
9 use CGI::Carp qw( fatalsToBrowser );
10
11 if ( param ) {
12 my ( $parser, $document, $forums, $forum, $name, $erase );
13
14 my $file = "forums.xml";
15
16 open XML, "+< ../htdocs/XML/$file" or die "Could not open: $!";
17 flock XML, LOCK_EX;
18
19 $parser = new XML::DOM::Parser;
20 $document = $parser->parse( \*XML );
21 $forums = $document->getDocumentElement;
22
23 foreach $forum ( $forums->getElementsByTagName( "forum" ) ) {
24 $file = $forum->getAttribute( "filename" );
25 if ( $file eq param( "file" ) ) {
26 $file =~ /^\w+\.xml$/ or die "Not a valid file: $!";
27 unlink( "../htdocs/XML/$file" ) or die
28 "Could not unlink: $!";
29 $forums->removeChild( $forum );
30 }
31 }
32
33 seek XML, 0, 0;
34 truncate XML, 0;
35 $document->print( \*XML );
36 close XML;
37 print redirect( "default.pl" );
38
39 }
40 else {
41 print redirect( "error.html" );
42 }
```