I only want to print the table names from my DB - mysql

Question

Here is my code. I get an internal server error with this. The subroutine is a clone from a book. So it is good to go. I just cannot get these tables to be on the screen by the time I look at the site. Is there anything that you guys see I am doing wrong?
#!/usr/bin/perl -T
use 5.010;
use DBI; #this is for database connections.
use CGI qw/:standard/;
use CGI::Carp qw(fatalsToBrowser);
#my $driver = "mysql";
my $database = "myown";
my $hostname = "whereitis";
my $dsn = "longblabla";
my $userid = "memyselfandI";
my $password = "onlymetoknow";
my $page1 = "Tables in the database: " . $database;
my $dbh = DBI->connect( $dsn, $userid, $password ) or die $DBI::errstr;
print
header,
start_html(
-title => $page1,
-meta => {
'viewport' => 'width=device-width, initial-scale=1',
'copyright' => 'copyright 2015 Noel Villaman'
},
-style => [
{ -src => 'bootstrap.min.css' },
{ -src => 'cgicssjs/style1.css' }
]
),
h1( $page1 ),
div( table_names( $dbh->table_info() ) ),
hr,
"\n";
# Disconnect from the database.
$dbh->disconnect();
print end_html;
sub table_names {
my $names = $_[0];
### Create a new statement handle to fetch table information
my $tabsth = $names; #$dbh->table_info();
### Print the header
print "<h1>Table Name</h1>";
print "<h3>===============</h3>";
### Iterate through all the tables...
while ( my ( $qual, $owner, $name, $type, $remarks ) = $tabsth->fetchrow_array() ) {
### Tidy up NULL fields
foreach ( $qual, $owner, $name, $type, $remarks ) {
$_ = "N/A" unless defined $_;
}
### Print out the table metadata...
print "<h3>$name</h3>";
}
exit;
}

Answer 1

In a comment, you say that you don't think that you can see the web server error log. It is ridiculous to try to develop a CGI program without access to the server error log. You should try to get that fixed as a matter of urgency.
But in the mean time, you can work round this restriction by adding the following near the top of your code.
use CGI::Carp 'fatalsToBrowser';
That will copy the error log messages to your browser so you can see them. But remember to remove or comment out that line before the code goes into production (not that this code will ever go into production in any meaningful way - I realise it's homework).
While you're editing that part of your code, also add:
use strict;
use warnings;
You should add these lines to every Perl program you write and fix all the errors and warnings that they give you.
So what's the problem with this code? I suspect that running it from the browser, you'll get an error about there being no CGI header line. That's because you exit() the program from the end of your table_names() subroutine. So the program never gets back from calling the table_names() subroutine and your main print() statement never gets executed - and that includes the header().
Also, in your main print() statement, you print the value returned from table_names(). But table_names() doesn't return anything. You need to change the logic in table_names() so that it returns the HTML it creates rather than printing it directly. Printing it directly will put it in the wrong place in the output stream.
One other point that I don't expect you're in any position to do anything about... CGI is pretty much a dead technology. This course is teaching you stuff that would have been useful fifteen years ago. Perhaps you could point your teacher at CGI::Alternatives and ask if he or she would consider teaching something that is more relevant to how web development is done today.
Update: The simplest fix is probably to split up your print statement so that things happen in the right order.
# Print all the start page stuff
print
header,
start_html(
-title => $page1,
-meta => {
'viewport' => 'width=device-width, initial-scale=1',
'copyright' => 'copyright 2015 Noel Villaman'
},
-style => [
{ -src => 'bootstrap.min.css' },
{ -src => 'cgicssjs/style1.css' }
]
),
h1( $page1 );
# No need to call print here as table_names
# does its own printing
table_names( $dbh->table_info() );
# Print all the end of page stuff.
print
hr,
"\n";
You'll still need to remove the exit() from the end of table_names, otherwise the program will never return from that subroutine.
Also, by doing this you lose a <div> around the output from table_names. Fixing that is left as an exercise for the reader.