Work as fast as you can without being careless. Good luck and do well!
Please write your name or username here: _________________________________
Correct answers are written in blue
1. (3 points) Write the HTML for a form like this:
Note: the form contains a text field and password field inside a 2x2 table.
Call the two fields uname and pword respectively. Make the
form POST the data to the following script:
http://tucotuco:19800/cgi-bin/simpleCheck
Please write the HTML code here (just the form not the whole HTML document):
The answer is:
As in C == is the equality operator and = is used
for assignment (as in the first two statements that assign 0 to
$i and 1 to $j).
The question now
boils down to the value returned by an assignment statement: an assignment
statement returns the value of its right hand side. So in this case 2
is returned, and 2 being different from 0 it is counted
as being true, so the print $i branch is going to be executed.
Since $i has been made 2 by this very test, the program
will print this number. Therefore the right answer to this question is: 2.
Admittedly this is a trick (or treat?) question. But it's also a classic.
2.2 (1.5 points) Same program as above with only $i = 0 in the condition
for the if statement.
The answer is:
This is a variation on the previous question but it's not easier even if you have solved
the first one right. The correct answer is 1, because $j will be
printed.
The reason behind this is that $i will be set to 0
but the returned value (which is 0) will make the if statement
direct execution towards the else branch. $j, which is set to 1
in the beginning, will be printed.
3. Your Apache directory structure looks like this:
What will happen when you call this script with a web browser? Why?
The server will run as user nobody and the script is executable only by you.
So the server won't be able to start your script and the user will see an error message in
her browser.
6. (3 points) What's the output of the following CGI.pm function call:
print $query->radio_group(-name=>'type',
-values=>['radio', 'select', 'check', 'open'],
-default=>'radio',
-linebreak=>'true',
-labels=>{
'radio' => ' Create a RADIO question',
'select' => ' Create a SELECT question',
'check' => ' Create a CHECK all that apply question',
'open' => ' Create an OPEN-ended (short answer) question'
});
Assume that
$query is a CGI object and that CGI.pm is used.
<INPUT TYPE="radio" NAME="type" VALUE="radio" CHECKED> Create a RADIO question
<BR><INPUT TYPE="radio" NAME="type" VALUE="select"> Create a SELECT question
<BR><INPUT TYPE="radio" NAME="type" VALUE="check"> Create a CHECK all that apply question
<BR><INPUT TYPE="radio" NAME="type" VALUE="open"> Create an OPEN-ended (short answer) question
<BR>
7. (4 points) Write the part that's missing from the simpleCheck script
presented below:
#!/usr/bin/perl
use CGI;
$query = new CGI;
print $query->header, $query->start_html;
if ($query->request_method eq 'GET') {
&show_form; # don't write this
} else {
# write this part
}
print $query->end_html;
The script is supposed to check that the username typed by the user is
admin and the password letmein. It should print
a simple message that states whether the check was or was not successful.
Note: do not write subroutine show_form (which outputs
the HTML that you have produced in problem 1). Refer to problem 1 in this
exam (above) for the names of the two fields and use the space below for
the code you write:
Then your server will be checked and if needed restarted
There was a similar question in homework 6 that had different settings.
This particular setting was also the recommended setting for our servers,
so this question was easy.
9. (1.5 points) From /u/username/httpd/logs which of the following commands
can be used to start your server (check all that apply).
The second option is correct because it points to both the binary and its location in an
absolute way. There's no ambiguity about this. So the last option falls. That leaves us with
three more to check.
The k switch on starthttpd is used to kill the server, as
explained in the lab and lecture notes, and that takes care of that option too.
The fourth one is equivalent to the second one (given the location) while the third one can't
be (for the same reason).
So only two answers are correct and the rest are incorrect.
10. (1.5 points) What's the output of this simple Perl program:
There was a similar problem on homework 6, and it's the same process that we
made use of in the URL finder in homework 5. All contiguous sequences of numbers are
detected and printed. We print them all on one line, but we also count them,
and since $i is first incremented
and then printed (++$i)
the count starts at 1.
14. (1 point) The CGI specifies an interface whereby a CGI script called with method
GET should expect to receive the data from the server in:
prevent the form from being submitted in certain circumstances
guarantee JavaScript syntax is being followed strictly
(return is required)
invoke the validateForm routine
monitor the events and call the corresponding event handler
I mentioned in the lab when I demonstrated how the form works that if you want your
check to have any impact at all you'd want to make sure that when the result of the
check is false the form does not get submitted. return is
forcing this value to be propagated up the hirearchy, and thus it helps prevent the
form from being submitted when it shouldn't. It is the link between the functions
that check if the form is properly filled in and the submission mechanism of the
form.
16. (2 points) Which of the following is a valid way to embed an applet class named
scribble into a web page? Select all answers that look valid to
you:
As discussed in class (!)
the .class extension is assumed so if
it's missing there's no harm. No harm either if it's specified, since that's the expected
standard format anyway. The other three options are blatantly wrong so I won't spend more
time with them here.
17. (1 point) You're using GD.pm to draw pictures. What does the following
code do (if anything):
$image->line(0, 10, 20, 30);
draws a line from (0, 20) to (10, 30)
draws a line from (0, 10) to (20, 30)
draws the outline of a box whose left,
top corner is at (0, 10) and that is 20 pixels wide and 30 pixels high
nothing - this code
does not compile because it does not provide the correct number of arguments
nothing - this code does not compile because the arguments
are in the wrong order
The documentation says a color needs to be specified as a fifth argument. This
library is pretty strict and the method doesn't work without that parameter. A
few of you have tried this out for homework 6 and have observed it directly.
18. (1 point) What is the output of the following Perl program:
#!/usr/bin/perl
@a = (1, 2, 3, 4);
print $#a;
The index of the last element of list @a is 3.
19. (1 point) Assume the following Perl program
called one:
#!/usr/bin/perl
print $ARGV[1];
What is the output of the program when the program is called
as follows:
./one my three arguments
The second command line argument will be printed.
20. Here's a program called database:
#!/usr/bin/perl
$function = $ARGV[0];
$animal = $ARGV[1];
$habitat = $ARGV[2];
dbmopen($zoo, "/u/username/databases/zoo", 0644);
if ($function eq 'add') {
if ($zoo{$animal}) { $zoo{$animal} .= ":$habitat"; }
else { $zoo{$animal} = $habitat; }
print "Thanks for adding ($animal, $habitat)";
} elsif ($function eq 'search') {
print $zoo{$animal};
} elsif ($function eq "delete") {
# this space for rent
} else { print "Command $function not implemented yet."; }
dbmclose(%zoo);
Assume that the database is empty and the script is called
four times in this sequence:
./database add camel desert
./database add camel "new york"
./database add camel desert
./database search camel
20.1 (2.5 points) What output will be produced after the fourth call:
The .= operator works for strings like += for numbers.
This is the reason for which the entry for $zoo{$animal} is going to
keep growing. Now notice how the entry is checked to make sure it grows only if
there is already something in there. If this is the first habitat we're storing
then = will be used instead of .=. So the last option
is incorrect, because of the leading :. The order in which we grow
the sequence of habitats is the order of the calls, so new york
is in the middle so the right answer can't be the third one either.
20.2 (1 point) Do we need the double quotes around new york in the
second call? Why?
Yes, we need to protect the blank space from being interpreted as a delimiter
when @ARGV is created.
20.3 (1 point) What's the final output of the program if we do not use double quotes
at all?
Same reasoning as before only york gets lost.
20.4 (2.5 points) Add a
delete <animal>
functionality to this program by writing one or more lines of code to
replace the
# this space for rent
comment in the program. Use the space below to write your answer:
delete $zoo{$animal}
We have covered this in the second part of homework 4
!)
the