Some words on getting started with Moss.

Moss-README.rst

Checking Plagiarism with Moss

Moss (Measure of Software Similarity) is a service that is used to check for plagiarism with programming assignments.

Getting Started with Moss

Moss is simply a command-line script that sends the program files to a server. You give the moss script criteria (such as the programming language), ship off the files, and are returned with a link where you can view the results.

To get started with Moss, you need to register for it. Directions on how to register are on the Moss website, in the "Register for Moss" section. If you don't really understand the directions on the website, here's the gist of it: Email [email protected] a message with the body:

registeruser
mail username@domain

Where username@domain is your email address.

In a little while, you'll be given an email that has a moss script with a unique user id just for you. It's a Perl script, so be sure your system can run Perl programs!

Options

There are detailed usage instructions in the moss script, but I'll cover two basic script options that should help you get started.

Specifying a language with -l

First off, the -l option tells the script what language to process the programs under. So the option -l java will process the files you send as java files.

Providing a label with -c

Next, the -c option allows you to give a comments string that will appear on the report that Moss creates. This allows you to label the generated report for context.

A sample Moss command

Here's a simple one:

moss -l java -c "CS 46A Spring 2014 - Homework 1 Final" *.java

This will grade all of the java files in the current directory (*.java), specifying to Moss that the files are java files (-l java), and giving the report a label of CS 46A Spring 2014 - Homework 1 Final.

When you run this script, the files you specify will be sent to the Moss server, Once it's done generating the report, it will give you a link to the report on the command-line output.

Viewing Moss reports long after they've expired

The Moss report isn't saved on the server forever. It probably only lasts for a couple of weeks. If you want to see the report in the future, you would either have te send Moss the same files once more, or you can download them onto your machine. If you want to do the latter, you can do so with wget, for example:

wget -r -np http://moss.stanford.edu/results/619603464

!/usr/bin/perl

Please read all the comments down to the line that says "TOP".

These comments are divided into three sections:

#1. usage instructions
#2. installation instructions
#3. standard copyright

Feel free to share this script with other instructors of programming

classes, but please do not place the script in a publicly accessible

place. Comments, questions, and bug reports should be sent to

[email protected].

IMPORTANT: This script is known to work on Unix and on Windows using Cygwin.

It is not known to work on other ways of using Perl under Windows. If the

script does not work for you under Windows, you can try the email-based

version for Windows (available on the Moss home page).

Section 1. Usage instructions

moss [-l language] [-d] [-b basefile1] ... [-b basefilen] [-m #] [-c "string"] file1 file2 file3 ...

The -l option specifies the source language of the tested programs.

Moss supports many different languages; see the variable "languages" below for the

full list.

Example: Compare the lisp programs foo.lisp and bar.lisp:

moss -l lisp foo.lisp bar.lisp

The -d option specifies that submissions are by directory, not by file.

That is, files in a directory are taken to be part of the same program,

and reported matches are organized accordingly by directory.

Example: Compare the programs foo and bar, which consist of .c and .h

files in the directories foo and bar respectively.

moss -d foo/.c foo/.h bar/.c bar/.h

Example: Each program consists of the *.c and *.h files in a directory under

the directory "assignment1."

moss -d assignment1//.h assignment1//.c

The -b option names a "base file". Moss normally reports all code

that matches in pairs of files. When a base file is supplied,

program code that also appears in the base file is not counted in matches.

A typical base file will include, for example, the instructor-supplied

code for an assignment. Multiple -b options are allowed. You should

use a base file if it is convenient; base files improve results, but

are not usually necessary for obtaining useful information.

IMPORTANT: Unlike previous versions of moss, the -b option always

takes a single filename, even if the -d option is also used.

Examples:

Submit all of the C++ files in the current directory, using skeleton.cc

as the base file:

moss -l cc -b skeleton.cc *.cc

Submit all of the ML programs in directories asn1.96/* and asn1.97/*, where

asn1.97/instructor/example.ml and asn1.96/instructor/example.ml contain the base files.

moss -l ml -b asn1.97/instructor/example.ml -b asn1.96/instructor/example.ml -d asn1.97//.ml asn1.96//.ml

The -m option sets the maximum number of times a given passage may appear

before it is ignored. A passage of code that appears in many programs

is probably legitimate sharing and not the result of plagiarism. With -m N,

any passage appearing in more than N programs is treated as if it appeared in

a base file (i.e., it is never reported). Option -m can be used to control

moss' sensitivity. With -m 2, moss reports only passages that appear

in exactly two programs. If one expects many very similar solutions

(e.g., the short first assignments typical of introductory programming

courses) then using -m 3 or -m 4 is a good way to eliminate all but

truly unusual matches between programs while still being able to detect

#3-way or 4-way plagiarism. With -m 1000000 (or any very

large number), moss reports all matches, no matter how often they appear.

The -m setting is most useful for large assignments where one also a base file

expected to hold all legitimately shared code. The default for -m is 10.

Examples:

moss -l pascal -m 2 *.pascal

moss -l cc -m 1000000 -b mycode.cc asn1/*.cc

The -c option supplies a comment string that is attached to the generated

report. This option facilitates matching queries submitted with replies

received, especially when several queries are submitted at once.

Example:

moss -l scheme -c "Scheme programs" *.sch

The -n option determines the number of matching files to show in the results.

The default is 250.

Example:

moss -c java -n 200 *.java

The -x option sends queries to the current experimental version of the server.

The experimental server has the most recent Moss features and is also usually

less stable (read: may have more bugs).

Example:

moss -x -l ml *.ml

Section 2. Installation instructions.

You may need to change the very first line of this script

if perl is not in /usr/bin on your system. Just replace /usr/bin

with the pathname of the directory where perl resides.

#3. Standard Copyright

Copyright (c) 1997 The Regents of the University of California.

All rights reserved.

Permission to use, copy, modify, and distribute this software for any

purpose, without fee, and without written agreement is hereby granted,

provided that the above copyright notice and the following two

paragraphs appear in all copies of this software.

IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR

DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT

OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF

CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,

INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY

AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS

ON AN "AS IS" BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATION TO

PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.

STOP. It should not be necessary to change anything below this line

to use the script.

use IO::Socket;

As of the date this script was written, the following languages were supported. This script will work with

languages added later however. Check the moss website for the full list of supported languages.

@languages = ("c", "cc", "java", "ml", "pascal", "ada", "lisp", "scheme", "haskell", "fortran", "ascii", "vhdl", "perl", "matlab", "python", "mips", "prolog", "spice", "vb", "csharp", "modula2", "a8086", "javascript", "plsql", "verilog");

$server = 'moss.stanford.edu';
$port = '7690';
$noreq = "Request not sent.";
$usage = "usage: moss [-x] [-l language] [-d] [-b basefile1] ... [-b basefilen] [-m #] [-c "string"] file1 file2 file3 ...";

The userid is used to authenticate your queries to the server; don't change it!

$userid=515577103;

Process the command line options. This is done in a non-standard

way to allow multiple -b's.

$opt_l = "c"; # default language is c
$opt_m = 10;
$opt_d = 0;
$opt_x = 0;
$opt_c = "";
$opt_n = 250;
$bindex = 0; # this becomes non-zero if we have any base files

while (@argv && ($_ = $ARGV[0]) =~ /^-(.)(.*)/) {
($first,$rest) = ($1,$2);

shift(@ARGV);
if ($first eq "d") {
    $opt_d = 1;
    next;
}
if ($first eq "b") {
    if($rest eq '') {
        die "No argument for option -b.\n" unless @ARGV;
        $rest = shift(@ARGV);
    }
    $opt_b[$bindex++] = $rest;
    next;
}
if ($first eq "l") {
    if ($rest eq '') {
        die "No argument for option -l.\n" unless @ARGV;
        $rest = shift(@ARGV);
    }
    $opt_l = $rest;
    next;
}
if ($first eq "m") {
    if($rest eq '') {
        die "No argument for option -m.\n" unless @ARGV;
        $rest = shift(@ARGV);
    }
    $opt_m = $rest;
    next;
}
if ($first eq "c") {
    if($rest eq '') {
        die "No argument for option -c.\n" unless @ARGV;
        $rest = shift(@ARGV);
    }
    $opt_c = $rest;
    next;
}
if ($first eq "n") {
    if($rest eq '') {
        die "No argument for option -n.\n" unless @ARGV;
        $rest = shift(@ARGV);
    }
    $opt_n = $rest;
    next;
}
if ($first eq "x") {
    $opt_x = 1;
    next;
}
#
# Override the name of the server.  This is used for testing this script.
#
if ($first eq "s") {
    $server = shift(@ARGV);
    next;
}
#
# Override the port.  This is used for testing this script.
#
if ($first eq "p") {
    $port = shift(@ARGV);
    next;
}
die "Unrecognized option -$first.  $usage\n"; 

}

Check a bunch of things first to ensure that the

script will be able to run to completion.

Make sure all the argument files exist and are readable.

print "Checking files . . . \n";
$i = 0;
while($i < $bindex)
{
die "Base file $opt_b[$i] does not exist. $noreq\n" unless -e "$opt_b[$i]";
die "Base file $opt_b[$i] is not readable. $noreq\n" unless -r "$opt_b[$i]";
die "Base file $opt_b is not a text file. $noreq\n" unless -T "$opt_b[$i]";
$i++;
}
foreach $file (@argv)
{
die "File $file does not exist. $noreq\n" unless -e "$file";
die "File $file is not readable. $noreq\n" unless -r "$file";
die "File $file is not a text file. $noreq\n" unless -T "$file";
}

if ("@argv" eq '') {
die "No files submitted.\n $usage";
}
print "OK\n";

Now the real processing begins.

$sock = new IO::Socket::INET (
PeerAddr => $server,
PeerPort => $port,
Proto => 'tcp',
);
die "Could not connect to server $server: $!\n" unless $sock;
$sock->autoflush(1);

sub read_from_server {
$msg = <$sock>;
print $msg;
}

sub upload_file {
local ($file, $id, $lang) = @_;

The stat function does not seem to give correct filesizes on windows, so

we compute the size here via brute force.

open(F,$file);
$size = 0;
while (<F>) {
    $size += length($_);
}
close(F);

print "Uploading $file ...";
open(F,$file);
$file =~s/\s/\_/g;    # replace blanks in filename with underscores
print $sock "file $id $lang $size $file\n";
while (<F>) {
    print $sock $_;
}
close(F);
print "done.\n";

}

print $sock "moss $userid\n"; # authenticate user
print $sock "directory $opt_d\n";
print $sock "X $opt_x\n";
print $sock "maxmatches $opt_m\n";
print $sock "show $opt_n\n";

confirm that we have a supported languages

print $sock "language $opt_l\n";
$msg = <$sock>;
chop($msg);
if ($msg eq "no") {
print $sock "end\n";
die "Unrecognized language $opt_l.";
}

upload any base files

$i = 0;
while($i < $bindex) {
&upload_file($opt_b[$i++],0,$opt_l);
}

$setid = 1;
foreach $file (@argv) {
&upload_file($file,$setid++,$opt_l);
}

print $sock "query 0 $opt_c\n";
print "Query submitted. Waiting for the server's response.\n";
&read_from_server();
print $sock "end\n";
close($sock);

From the script posted above:

Feel free to share this script with other instructors of programming
classes, but please do not place the script in a publicly accessible

You should probably delete the above comment.

@JeffCave
That must be outdated, it used to be only distributed to programming instructors and faculty but that has since changed, see the website:
https://theory.stanford.edu/~aiken/moss/

Moss is being provided in the hope that it will benefit the educational community. Moss is fast, easy to use, and free. In the past, access has been restricted to instructors and staff of programming courses. This is no longer the case, and anyone may obtain a Moss account.

Would this be able to run on a MacOS? If so, how?

@ipgogra The moss tool interacts with the Moss service. Uploading to Moss should work on Mac as with any other system.

@danielmai Thanks for responding. That's what I thought. I'm looking to use this for a class that I'm TA-ing for. Plagiarism is pretty rampant and hopefully we can detect it more effectively.

It uploads the file successfully, but I'm getting a 404 when I try to open the results URL. Is anyone facing the same issue? Is MOSS down?

@abhilash1in
Same here, uploading and processing seems to go fine, but reports are not accessible:

It uploads the file successfully, but I'm getting a 404 when I try to open the results URL. Is anyone facing the same issue? Is MOSS down?

I'm facing the same issue. Any updates yet?

I meet the 404 problem too. Any advice? thank you.

ı have 404 problem. Yesterday everything is worked but today not :(
Do you know any solution ?

I want to check for plagiarism a bunch of homeworks written in 8086 assembly language using MOSS script, but all the time I receive the message "File 1 File 2 Lines Matched / No matches were found in your submission.", even if I send the same file. The options are: "./moss -l a8086 -m 3 file1.asm file1.asm". There is expected another form for MOSS command or for assembly sources?

I want to check for plagiarism a bunch of homeworks written in 8086 assembly language using MOSS script, but all the time I receive the message "File 1 File 2 Lines Matched / No matches were found in your submission.", even if I send the same file. The options are: "./moss -l a8086 -m 3 file1.asm file1.asm". There is expected another form for MOSS command or for assembly sources?

Same confusion here.

I want to check for plagiarism a bunch of homeworks written in 8086 assembly language using MOSS script, but all the time I receive the message "File 1 File 2 Lines Matched / No matches were found in your submission.", even if I send the same file. The options are: "./moss -l a8086 -m 3 file1.asm file1.asm". There is expected another form for MOSS command or for assembly sources?

Same confusion here.

I used a blind approach, ASCII language which of course is not much help. I think that a8086 is a language not very used in assignments, as a result not maintained.

Codequiry uses Moss plagiarism checking software and has an advanced support for Java, C, C++, and Python.

I am unable to run the code for matlab files
This is the error I get

% ../moss.pl -l matlab -c "codecheck" ./*.mlx
% Checking files . . .
% File ./A01.mlx is not a text file. Request not sent.

How do I fix these? matlab files are supposed to be .mlx format

@danielmai i tried running it on Windows after installing Strawberry Perl , but the '*' extension does not work

so if i try to select all .py files using ' *.py ' command, it doesn't work .. can you help ?

@danielmai i tried running it on Windows after installing Strawberry Perl , but the '*' extension does not work

so if i try to select all .py files using ' *.py ' command, it doesn't work .. can you help ?

The easiest way to solve it is to install Windows Subsystem for Linux and run your command inside Ubuntu command line like perl moss.pl -l python *.py. It works for me :)

Codequiry uses Moss plagiarism checking software and has an advanced support for Java, C, C++, and Python.

Does Codequiry still uses Moss?