Description
It is possible in response to student queries that there will be minor changes to this specification, most likely in subset 2,
Autotests are incomplete. More will be added.
Aims
This assignment aims to give you practice in Perl programming generally a clear concrete understanding of sed’s core semantics
Your task in this assignment is to implement Speed, a subset of the important Unix/Linux tool Sed.
You will do this in Perl hence the name Speed
Sed is a very complex program which has many commands. You will implement only a few of the most important commands. You will also be given a number of simplifying assumptions, which make your task easier.
Speed is a subset of POSIX-compatible sed with extended regular expressions. On a CSE systems you would run sed –posix -r You must implement Speed in Perl only. See the Permitted Languages section below for more information. Reference implementation
Many aspects of this assignment are not fully specified in this document; instead, you must match the behaviour of the reference implementation: 2041 speed
Provision of a reference implementation is a common method to provide or define an operational specification, and it’s something you will likely need to do after you leave UNSW.
Discovering and matching the reference implementation’s behaviour is deliberately part of the assignment, and will take some thought.
Speed Commands
Subset 0
In subset 0 speed.pl will always be given a single Speed command as a command-line argument.
The sed command will be one of ‘p’,’q’ and ‘s’ (see below).
The only other command-line argument possible in subset 0 is the -n option.
Input files will not be specified in subset 0. For subset 0 speed.pl need only read lines from standard input.
Subset 0: addresses
Speed commands can optionally be preceded by an address specifying the line(s) they apply to, In subset 0, this address can either be line number or a regex.
The line number must be a positive integer.
The regex must be delimited with slash / characters.
Subset 0 & 1: Regexes
In subset 0 and 1 you can assume backslash does not appear in address regexes
In subset 0 and 1, you can assume backslash does not appear in address regexes.
In subset 0 and 1, you can assume the character used to delimit the regex can not appear in the regex itself.
In subset 0, regexes are delimited with slash / characters so you can assume slashes do not appear in regexes.
In all subsets, you can assume the regex is correct. You do not have to check for errors in the regex.
In all subsets, you can assume the regex is compatible with Perl. In other words, the regex can be used as Perl regular expressions and will have the same meaning..
Subset 0: q – quit command
The Speed q command causes speed.pl to exit, for example:
$ seq 1 5|2041 speed 3q
1
2
3
$ seq 10 15|2041 speed /.1/q
10
11
Subset 0: p – print command
The Speed p commands prints the input line, for example:
$ seq 1 5|2041 speed 2p
1
2
2
3
4
5
Subset 0: d – delete command
The Speed d commands deletes the input line, for example:
$ seq 1 5|2041 speed 4d
1
2
3
5
Subset 0: s – substitute command
The Speed s command replaces the specified regex on the input line.
In subset 0, the regex must be delimited with slash / characters.
In subset 1, you can assume that slash / characters do not appear in the regex or replacement string.
In subset 0 & 1, you can assume the replacement string is compatible with Perl and can be used in a Perl substitute command with the same effect.
$ seq 1 5|2041 speed ‘s/[15]/zzz/’ zzz 2
3 4 zzz
The substitute command can followed optionally by the modifier character g, for example:
$ echo Hello Andrew|2041 speed ‘s/e//’
Hllo Andrew
$ echo Hello Andrew|2041 speed ‘s/e//g’
Hllo Andrw
g is the only permitted modifier character.
Subset 0: -n command line option
The Speed -n command line option stops input lines being printed by default.
$ seq 1 5|2041 speed -n 3p
3
Subset 1
Subset 1 is more difficult. You will need to spend some time understanding the semantics (meaning) of these operations, by running the reference implementation, or researching the equivalent sed operations.
p , g q p
Note the assessment scheme recognises this difficulty.
Subset 1: addresses
In subset 1, $ can be used as an address. It matches the last line, for example
$ seq 1 5|2041 speed ‘$d’
1
2
3
4
In subset 1, Speed commands can optionally be preceded by a comma separated pair of address specifying the start and finish of the range of lines the command applies to, for example:
$ seq 10 21|2041 speed 3,/2/d
10
11
21
Subset 1: s – substitute command
$ seq 1 5|2041 speed ‘sX[15]XzzzX’ zzz 2
3 4 zzz
In subset 0 & 1, you can assume the replacement string is compatible with Perl and can be used in a Perl substitute command with the same effect.
In subset 1, you can assume that the character used to delimit the substitute command does not appear in the regex or replacement string.
Subset 1: Multiple Commands
In subset 1, multiple Speed commands can be supplied separated by semicolons ;, for example:
$ seq 1 5|2041 speed ‘4q;/2/d’
1
3
4
In subset 1, you can assume semicolons do not occur anywhere inside Speed commands
Subset 1: -f command line option
The Speed -f reads Speed commands from the specified file, for example
$ echo 4q >commands.speed $ echo /2/d >>commands.speed $ seq 1 5|2041 speed -f commands.speed
1
3
4
Subset 1: Input Files
In subset 1, input files can be specified on the command line:
$ seq 1 2 >two.txt $ seq 1 5 >five.txt $ 2041 speed ‘4q;/2/d’ two.txt five.txt
1
1
2
Subset 1: Comments & White Space
In subset 1, whitespace can appear before and after commands & addresses and ‘#’ can be used as a comment character, for example:
$ seq 24 42|2041 speed ‘ 3, 17 d # comment’
24
25
41
42
In subset 1, you can assume newline does not appear in Speed commands specified as a command line argument.
Subset 2
Subset 2 is even more difficult. You will need to spend considerable time understanding the semantics of these operations, by running the reference implementation, and/or researching the equivalent sed operations.
Note the assessment scheme recognises this difficulty.
Subset 2: Regexes
Subset 2: s – substitute command
In subset 2 you can not assume, that the replacement string is compatible with Perl and you can not assume it can be used in a Perl substitute command with the same effect.
Subset 2: -i command line option
The Speed -i command line options replaces file contents with the output of the Speed commands. You should use a temporary file.
$ seq 1 5 >five.txt $ cat five.txt
1
2
3
4
5
$ 2041 speed -i /[24]/d five.txt $ cat five.txt
1
3
5
Subset 2: Multiple Commands
In subset 2, semicolons can appear inside Speed commands.
$ echo ‘Punctuation characters include . , ; :’|2041 speed ‘s/;/semicolon/g;/;/q’ Punctuation characters include . , semicolon :
In subset 2, newline can be used to separate Speed commands passed a command-line argument.
Subset 2: : – label command
The Speed : command indicates where b and t commands should continue execution.
There can not be an address before a label command.
Subset 2: b – branch command
The Speed b command branches to the specified label, if the label is omitted, it branches to end of the script.
Subset 2: t – conditional branch command
The Speed t command behaves the same as the b command except it branches only if there has been a successful substitute command since the last input line was read and since the last t command.
Subset 2: a – append command
The Speed a command appends the specified text.
Subset 2: i – insert command
The Speed i command inserts the specified text.
There can not be an address before an insert command.
Subset 2: c – change command
The Speed c command replaces the selected lines with the specified text.
Other Sed Features
You do not have to implement in Speed sed features and commands other than those described above.
For example sed on CSE systems provides extra commands including {} D h H g G l n p T w W x y which are not part of Speed For example, sed on CSE systems provides extra commands including {} D h H g G l n p T w W x y which are not part of Speed. For example, sed on CSE systems adds extra syntax to addresses including feature involving the characters: ! + ~ 0 . These are not part of Speed.
For example, sed on CSE systems has a number of command-line options other than -i, -n and -f. These are not part of Speed The reference implementation implements many of these extra sed features and commands.
The marking will not test your code on these these extra features and commands.
You do not have to check for these extra features and commands.
You will not be penalized if you choose to implement any of these extra features and commands. Diary
19/06/19 16 00 17 30 coding implemented basic -n functionality
20/06/19 20 00 10 30 debugging found bug in command-line arguments
Include these notes in the files you submit as an ASCII file named diary.txt.
Testing
Autotests
As usual, some autotests will be available:
$ 2041 autotest speed speed.pl …
You can also run only tests for a particular subset or an individual test:
$ 2041 autotest speed subset1 speed.pl …
$ 2041 autotest speed subset1_13 speed.pl …
If you are using extra Perl (.pl or .pm) files, include them on the autotest command line.
You can download the files used by autotest as a zip file or a tar file.
You will need to do most of the testing yourself.
Test Scripts
You should submit ten Shell scripts, named test00.sh to test09.sh, which run speed commands that test an aspect of Speed.
Your test script should check whether the test is passed or failed and print a suitable message.
Your test script should exit with status 0 if the test was passed and exit with status 0 if it was failed.
The test??.sh scripts do not have to be examples that your program implements successfully.
The test scripts should show how you’ve thought about testing carefully.
You are only expected to write test scripts testing parts of Speed you have attempted to implement. For example, if you have not attempted subset 2 you are not expected to write test scripts testing . Permitted Languages
Your programs must be written entirely in Perl.
Start speed.pl with:
#!/usr/bin/perl -w
If you want to run your code on a machine perl is not installed in /usr/bin/ you can alternatively start speed.pl like this:
#!/usr/bin/env perl use warnings;
Your answer must be Perl only. You can not use other languages such as Shell, Python or C.
You are permitted to use any Perl module installed on CSE servers.
Your Perl code should work with /usr/bin/perl on CSE servers.
Your Perl code should not generate warnings when run with /usr/bin/perl -w on CSE servers.
Assumptions/Clarifications
Like all good programmers, you should make as few assumptions as possible.
You can assume that only the arguments described above are supplied to speed commands. You do not have to handle other arguments.
You should match the output streams used by the reference implementations. It writes error messages to stderr: so should you.
You should match the exit status used by the reference implementation. It exits with status 1 after an error: so should you.
You can assume the directory containing your Perl files is in the environment variable $PERL5LIB.
You can assume arguments will be in the position and order shown in the usage message from the reference implementation. Other orders and positions will not be tested. Here is the usage message:
$ ./speed.pl –help
usage: speed.py [-i] [-n] [-f <script-file> | <sed-command>] [<files>…]
You can assume, Speed regular expressions and valid Perl regular expressions and are compatible with Perl. In other words, they can be used as Perl regular expressions and will have the same effect.
You can assume command line arguments, STDIN and all files contain only ASCII bytes.
You can assume all input lines in STDIN and in all files are terminated by a ‘ ‘ byte.
Speed error messages include the program name. It is recommended you use $0 however it also acceptable to hard-code the program name. The automarking and style marking will accept both. Change Log
Version 0.1 Initial release
Version 0.2$ as address added
clarification of subsets added
Version 0.3 change assignment name to Speed to avoid connection to derogratory term
Testing
When you think your program is working, you can use autotest to run some simple automated tests:
$ 2041 autotest speed
2041 autotest will not test everything. Always do your own testing.
Submission
When you are finished working on the assignment, you must submit your work by running give:
$ give cs2041 ass2_speed speed.pl diary.txt test??.sh [any-other-files]
13/04/2021exercise, the work you submit with give must be entirely your own.
You can run give multiple times.
Only your last submission will be marked.
You can check your latest submission on CSE servers with:
$ COMP(2041|9044) classrun -check ass2_speed
You can check the files you have submitted here.
This assignment will contribute 15 marks to your final COMP(2041|9044) mark
15% of the marks for assignment 2 will come from hand-marking. These marks will be awarded on the basis of clarity, commenting, elegance and style: in other words, you will be assessed on how easy it is for a human to read and understand your program.
5% of the marks for assignment 2 will be based on the test suite you submit.
80% of the marks for assignment 2 will come from the performance of your code on a large series of tests.
HD (85+) All subsets working; code is beautiful; great test suite and diary
DN (75+) Subset 1 working; good clear code; good test suite and diary
CR (65+) Subset 0 working; good clear code; good test suite and diary
PS (55+) Subset 0 passing some tests; code is reasonably readable; reasonable test suite and diary
PS (50+) Good progress on assignment, but not passing autotests
0% knowingly providing your work to anyone and it is subsequently submitted (by anyone).
0 FL for submitting any other person’s work; this includes joint work.
COMP(2041|9044)
academic submitting another person’s work without their consent; misconduct paying another person to do work for you.
Intermediate Versions of Work
You are required to submit intermediate versions of your assignment.
Every time you work on the assignment and make some progress you should copy your work to your CSE account and submit it using the give command below. It is fine if intermediate versions do not compile or otherwise fail submission tests. Only the final submitted version of your assignment will be marked.
All these intermediate versions of your work will be placed in a Git repository and made available to you via a web interface at https://gitlab.cse.unsw.edu.au/z5555555/21T1-comp2041-ass2_speed (replacing z5555555 with your own zID). This will allow you to retrieve earlier versions of your code if needed.
Attribution of Work
This is an individual assignment.
The work you submit must be entirely your own work, apart from any exceptions explicitly included in the assignment specification above. Submission of work partially or completely derived from any other person or jointly written with any other person is not permitted.
Assignment submissions will be examined, both automatically and manually, for such submissions.
Change Log
For all enquiries, please email the class account at [email protected]
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