1
Columbia University
cs3157 – Advanced Programming
Summer 2014, Lab
#2, 60ish points
June 9, 2014
Follow these step-by-step instructions. This
lab must be submitted electronically by Monday June
16th, 11:55 pm.
The
point of the labs is to teach and reinforce specific programming concepts, cut
time off your
homework assignment while trying to maintain your interest. If
you find them tedious or pointless, please
don’t hesitate to bring it to your
instructor’s attention (the same applies the opposite).
Step 1. Visual Editor
and Debugging (5 points)
A debugger is a program that allows you (the
programmer) to step through an executing program (i.e live,
real time) and
track internal information and monitor progress. This allows you to monitor
logical
progress and also track down errors.
Perldoc perldebug
Will
give you more information about the debugging environment. Executing the perl
command with the
-d flag will start perl in debugging mode. Try it….take one
of the scripts from lab1 and execute it
perl -d something.pl
(h gives you
help, q to quit, v shows you some code around you, etc).
The nice part about
eclipse is the ability of running the debugger in a visual environment, so that
you
don’t need to memorize random key commands. (That is a good thing and
bad). You have a choice if you
want to run it from the command line or visual
environment. Be aware that certain specific versions of
eclipse (older) and
certain versions of EPIC (older) have issues with the debug system, which causes
it to
work every other time J
Write up a paragraph or two about your
experience in running the debugging environment on one of the
lab scripts
from last lab and over the lab 2 assignments. Answer the following questions
after you are
done with the lab:
1) After using the debugger, did your
code work become easier or harder ?
2) Any issues with the perl debugger in
the clic lab ?
3) After using it to watch a variable what can you say about
perl variable scope ?
4) What is the difference between stepping over and
stepping through in regards to subs ?
5) How does the average rainfall in the
Sahara affect Perl development ?
Step 2 (20 points)
Create a perl file
called step2.pl. I am providing a file called “testip” to be used as a test
file.
2
Background information: Computer on the internet are identified
using a few standard conventions.
One of them are IP address. The format for
IP version 4, is 4 sets of numbers between 0-255. So your own
machine might
be 128.59.18.1 etc
1) Given a specific file (passed as a command line
argument (important) ) which contains among
other things, IP addresses, I
would like you to locate and count
any IP address in the file. For example
the ip address 255.234.255.1 (4 numbers separated by a
period).
NOTE: you
need to make sure none of the numbers are not larger than 255
2) I would also
like a printout of all the IP addresses, and the number of times it was seen in
the file.
Addresses can appear multiple times on a line…keep that in
mind.
3) I would like to know how much time has passed from the beginning and
end of the program run,
we would like to see how much time it took to
analyze. Lookup localtime command to see how to
grab the current time.
You
will need to loop through the file, find the ip address (use the regular
expressions covered in class on
Monday), and then keep a count of number of
each one seen. Once done, you can print them out in sorted
order in the
following format:
Processed file YYYYY
Number of unique IP:
3
123.123.123.123 9
12.12.112.2 7
23.125.123.256 2
..
File
analyzed in: 1 minute and 23 seconds
Step 3: (4 points)
Consider the
following Perl program:
#!/usr/bin/perl
use strict;
my(@list) = (5,
"Todd", 3, 2);
$list[2] += 4;
print "M1: ".$list[0]." ".$list[1]."
".$list[2]." ".$list[3]."
";
($list[1], $list[3]) = funky(@list);
print
"M2: ".$list[0]." ".$list[1]." ".$list[2]." ".$list[3]."
";
## End of main
program
sub funky {
my($v1, $v2, $v3) = @_;
print "F1: "." ".$v1."
".$v2." ".$v3.
" ".$_[0]." ".$_[1]." ".$_[2]."
".$_[3]."
";
$_[0]++;
print "F2: "." ".$v1." ".$v2." ".$v3.
"
".$_[0]." ".$_[1]." ".$_[2]." ".$_[3]."
";
$v3 = "Bill";
print "F3: "."
".$v1." ".$v2." ".$v3.
" ".$_[0]." ".$_[1]." ".$_[2]."
".$_[3]."
";
3
return($v3, $v2);
} ## Of function FUNKY
What did
you expect the output to look like and what did it actually look like ? Explain
(based on what
we covered in class) what is going on…
Step 4 New Process
monitor (20 points)
As demo-ed in class, you will write a simple process
monitor. You will use the output of the (ps –aux)
command to pick out all the
running pid->program names every 5 seconds. You will run your program
for
10 minutes printing out when a program starts, or stops.
As we
discussed you will need to run the ps command and then create a map list of the
current running
pid and process names. You will compare current to last map
(so if its at 10 seconds, you need to look
back at 5 seconds) for any
processes (pid) which are new to say process is new. Use the old one to look
at
the new one to detect dead process id.
Most of the code was demo-ed in
class, type it up and add comments.
Step 5: Moving information over CGI Intro
(4 points)
We started to talk about CGI in the last class. Forms are simple
ways of feeding information to the user
and having them interact with your
script in some way.
Here is your chance to start to play around with it.
Create a HTML page (feel free to use eclipse or your
favorite text editor)
(step5.html) should have the following code in
it:
<html><head><title>Step2
webpage</title></head>
<body>
<form
action=”step5a.pl.cgi” method=POST>
Enter something:
<input
type=”text” name=”t1”>
<input type=”submit”
value=”testpost”></form>
<HR>
<form
action=”step5b.pl.cgi” method=GET>
Enter Some text:
<input
type=”text” name=”t2”>
<input type=”submit”
value=”testget”></form>
</body>
</html>
step5a.pl.cgi
and step5b.pl.cgi should look like:
use strict;
4
my $time =
localtime;
print "Content-type: text/html
";
print
<<END_OF_PRINTING;
This is the time :
$time
END_OF_PRINTING
foreach my $vars (sort keys %ENV){
print
"<b>$vars</b>=";
print "$ENV{$vars}<BR>";
}
Describe
in a short paragraph what you see is the difference between get and post when
running the
cgi script. Do a quick search and read up on get and post in a
general sense. Which do you think is a better
way to work with ??
Note:
the webserver has perl in /usr/bin/perl
Step 6: More CGI and more basic
practice (5 points):
Copy and adopt the previous html file to a new file
called Step6.html. Have it call step6a.pl.cgi and
step6b.pl.cgi . In both
cases you need to process and display the input passed in, as a simple html
page
saying
I was given Key = …. With a value of = …
(for both input
types).
Hint: This means you need to parse out the arguments passed in.
remember to first split around the & sign
and then around the equal sign.
Example:
my ($pairs,$key,value);
foreach $pairs (split /&/
$inputstring){
#now cut the $pairs around the equal sign …..
Hint2: one of
the methods passes user input through ENV and one passes it through STDIN, but
you still
ENV for the length (see read method in perl)
HINT3: the scripts
are basically the same, get one to work and then copy and convert it for the
other task.