COMP9044 Week 02 Laboratory Exercises Solution

Before the lab you should re-read the relevant lecture slides and their accompanying examples.


Create a new directory for this lab called lab02, change to this directory, and fetch the provided code for this week by running these commands:
$ mkdir lab02
$ cd lab02
$ 2041 fetch lab02
Or, if you're not working on CSE, you can download the provided code as a zip file or a tar file.


There is a template file named counting_classes_answers.txt which you must use to enter the answers for this exercise.
Download counting_classes_answers.txt, or copy it to your CSE account using the following command:
$ cp -n /web/cs2041/20T2/activities/counting_classes/counting_classes_answers.txt .
The autotest scripts depend on the format of counting_classes_answers.txt so just add your answers don't otherwise change the file. In other words edit counting_classes_answers.txt:
gedit counting_classes_answers.txt &
The file classes.txt contains a list of CSE classes downloaded from myUNSW.
Download classes.txt, or copy it to your CSE account using the following command:
$ cp -n /web/cs2041/20T2/activities/counting_classes/classes.txt .

. Write a shell pipeline to print how many classes there are. Hint: the output of the pipeline should be:
441
. Write a shell pipeline to print how many different courses have classes. Hint: cut with the -f option will be useful here.
Hint: the output of the pipeline should be:
35
. Write a shell pipeline which will print the course with the most classes (and no other courses) and how many classes are in this course.
Hint: the output of the pipeline should be:
31 COMP1521
. Write a shell pipeline that prints the room most frequently-used room by CSE classes and how often it is used. Don't include the CSE lab rooms.
Hint: the output of the pipeline should be:
26 Quad 1042
. Write a shell pipeline that prints the most common day and hour in the week for classes to start and how many classes start at that time.
Hint: cut has a -c option.
Hint: the output of the pipeline should be:
20 Fri 11
COMP1000
COMP1511
COMP1521
COMP2041
COMP2511
COMP2521
COMP3331
COMP6441
COMP6841
COMP9044
COMP9311
COMP9313
COMP9331
COMP9417
When you think your program is working, you can use autotest to run some simple automated tests:
$ 2041 autotest counting_classes
Autotest Results
77% of 572 students who have autotested counting_classes_answers.txt so far, passed all autotest tests. 99% passed test q1 q2 q3 q4
98% passed test q5
80% passed test q6
When you are finished working on this exercise, you must submit your work by running give:
$ give cs2041 lab02_counting_classes counting_classes_answers.txt


Write a program digits.sh that reads from standard input and writes to standard output mapping all digit characters whose values are less than 5 into the character '<' and all digit characters whose values are greater than 5 into the character '>'. The digit character '5' should be left unchanged.
Sample Input Data Corresponding Output

1 234 5 678 9

< <<< 5 >>> >


I can think of 100's of other things I'd rather be doing than these 3 questions

I can think of <<<'s of other things I'd rather be doing than these < questions


A line with lots of numbers:
123456789123456789123456789
A line with all zeroes
000000000000000000000000000
A line with blanks at the end
1 2 3

A line with lots of numbers:
<<<<5>>>><<<<5>>>><<<<5>>>>
A line with all zeroes
<<<<<<<<<<<<<<<<<<<<<<<<<<<
A line with blanks at the end
< < <


Input with absolutely 0 digits in it Well ... apart from that one ...

Input with absolutely < digits in it Well ... apart from that one ...


1 2 4 8 16 32 64 128 256 512 1024
2048 4096 8192 16384 32768 65536

< < < > <> << >< <<> <5> 5<< <<<<
<<<> <<>> ><>< <><>< <<>>> >55<>

Hint: tr can be used.
When you think your program is working, you can use autotest to run some simple automated tests:
$ 2041 autotest digits
Autotest Results
99% of 557 students who have autotested digits.sh so far, passed all autotest tests. 99% passed test 1 2 3 4 5
When you are finished working on this exercise, you must submit your work by running give:
$ give cs2041 lab02_digits digits.sh


Write a shell script called echon.sh which given exactly two arguments, an integer n and a string, prints the string n times. For example:
./echon.sh 5 hello hello hello hello hello hello
./echon.sh 0 nothing ./echon.sh 1 goodbye goodbye
Your script should print exactly the error message below if it is not given exactly 2 arguments:
./echon.sh
Usage: ./echon.sh <number of lines> <string> ./echon.sh 1 2 3
Usage: ./echon.sh <number of lines> <string>
Also get your script to print this error message if its first argument isn't a non-negative integer:
./echon.sh hello world
./echon.sh: argument 1 must be a non-negative integer ./echon.sh -42 lines
./echon.sh: argument 1 must be a non-negative integer
Although its better practice to print your error messages to stderr its OK to print your error messages to stdout for this exercise.
Hint: you'll need to use the shell if, while and exit statements, shell arithmetic and the test command.
When you think your program is working, you can use autotest to run some simple automated tests:
$ 2041 autotest echon
Autotest Results
95% of 553 students who have autotested echon.sh so far, passed all autotest tests.
99% passed test 1
100% passed test 2
100% passed test 2
99% passed test 3 4 5 6
96% passed test 7
98% passed test 8
When you are finished working on this exercise, you must submit your work by running give:
$ give cs2041 lab02_echon echon.sh


Write a shell script file_sizes.sh which prints the names of the files in the current directory splitting them into three categories: small, medium-sized and large. A file is considered small if it contains less than 10 lines, medium-sized if contains less than 100 lines, otherwise it is considered large.
Your script should always print exactly three lines of output. Files should be listed in alphabetic order on each line. Your shell-script should match character-for-character the output shown in the example below. Notice the creation of a separate direcory for testing and the use of the script from the last question to produce test files. You could also produce test files manually using an editor.
mkdir test cd test ../echon.sh 5 text >a
../echon.sh 505 text >bbb
../echon.sh 17 text >cc
../echon.sh 10 text >d
../echon.sh 1000 text >e ../echon.sh 0 text >empty ls -l total 24
-rw-r--r-- 1 andrewt andrewt 25 Mar 24 10:37 a
-rw-r--r-- 1 andrewt andrewt 2525 Mar 24 10:37 bbb
-rw-r--r-- 1 andrewt andrewt 85 Mar 24 10:37 cc
-rw-r--r-- 1 andrewt andrewt 50 Mar 24 10:37 d
-rw-r--r-- 1 andrewt andrewt 5000 Mar 24 10:37 e
-rw-r--r-- 1 andrewt andrewt 0 Mar 24 10:37 empty
../file_sizes.sh
Small files: a empty
Medium-sized files: cc d Large files: bbb e rm cc d ../echon.sh 10000 . >lots_of_dots ls -l total 36
-rw-r--r-- 1 andrewt andrewt 25 Mar 24 10:37 a
-rw-r--r-- 1 andrewt andrewt 2525 Mar 24 10:37 bbb
-rw-r--r-- 1 andrewt andrewt 5000 Mar 24 10:37 e
-rw-r--r-- 1 andrewt andrewt 0 Mar 24 10:37 empty
-rw-r--r-- 1 andrewt andrewt 20000 Mar 24 10:39 lots_of_dots
../file_sizes.sh Small files: a empty Medium-sized files:
Large files: bbb e lots_of_dots
Hint: you can use the command wc to discover how many lines are in a file. You probably want to use the shell's back quotes, its if statement, and the test command.
When you think your program is working, you can use autotest to run some simple automated tests:
$ 2041 autotest file_sizes
Autotest Results
98% of 527 students who have autotested file_sizes.sh so far, passed the autotest test.
When you are finished working on this exercise, you must submit your work by running give:
$ give cs2041 lab02_file_sizes file_sizes.sh


This year UNSW has changed to much prettier format but also a format which it is much harder for a script to extract information from.

scraping_courses.sh OPTM
OPTM2111 Optometry 2A
OPTM2133 The Clinical Environment
OPTM2190 Introduction to Clinical Optometry
OPTM2211 Optometry 2B
OPTM2233 Optical Dispensing
OPTM2291 Primary Care Optometry
OPTM3105 Disease Processes of the Eye 1
OPTM3111 Optometry 3A
OPTM3131 Ocular Disease 3A
OPTM3133 Vision Science in the Consulting Room
OPTM3201 Ocular Imaging & Applied Vision Science OPTM3205 Disease Processes of the Eye 2
OPTM3211 Optometry 3B
OPTM3231 Ocular Disease 3B
OPTM3233 Working in the clinical environment
OPTM4110 Optometry 4A
OPTM4131 Clinical Optometry 4A
OPTM4151 Ocular Therapeutics 4A
OPTM4211 Optometry 4B
OPTM4231 Clinical Optometry 4B
OPTM4251 Ocular Therapeutics 4B
OPTM4271 Professional Optometry
OPTM4291 Optometry, Medicine & Patient Management
OPTM5111 Clinical Optometry 5A
OPTM5131 Specialist Clinical Optometry 5A
OPTM5151 Clinical Ocular Therapeutics 5A
OPTM5171 Research Project 5A
OPTM5211 Clinical Optometry 5B
OPTM5231 Specialist Clinical Optometry 5B
OPTM5251 Clinical Ocular Therapeutics 5B OPTM5271 Research Project 5B
OPTM6400 Optometric Preclinical Practice
OPTM6411 Contact Lenses
OPTM6412 Clinical Optometry 4A
OPTM6413 Anterior Eye Therapeutics
OPTM6421 Binocular Vision, Paediatrics and Low Vision
OPTM6422 Clinical Optometry 4B
OPTM6423 Therapeutics and the Posterior Eye
OPTM6424 Professional Optometry
OPTM7001 Introduction to Community Eye Health
OPTM7002 Epidemiology & Biostatistics for Needs Assessment
OPTM7003 Epidemiology of Blinding Eye Diseases
OPTM7004 Advocacy and Education in Community Eye Health OPTM7005 Eye Health Economics and Sustainability
OPTM7006 Eye Care Program Management
OPTM7007 Community Eye Health Project
OPTM7103 Behavioural Optometry 1
OPTM7104 Advanced Contact Lens Studies 1
OPTM7108 Research Skills in Optometry
OPTM7110 Public Health Optometry
OPTM7115 Visual Neuroscience
OPTM7117 Ocular Therapy 2
OPTM7203 Behavioural Optometry 2 OPTM7205 Specialty Contact Lens Studies
OPTM7213 Ocular Therapy
OPTM7301 Advanced Clinical Optometry
OPTM7302 Evidence Based Optometry
OPTM7308 Research Project
OPTM7444 Business Skills in Optometry
OPTM7511 Advanced Ocular Disease 1
OPTM7521 Advanced Ocular Disease 2
OPTM8511 Clinical paediatrics, low vision and colour vision
OPTM8512 Clinical Optometry 5A
OPTM8513 Clinical Ocular Therapy 5A
OPTM8518 Optometry Research Project A
OPTM8521 Clinical Contact Lenses
OPTM8522 Clinical Optometry 5B
OPTM8523 Clinical Ocular Therapy 5B OPTM8528 Optometry Research Project B scraping_courses.sh MATH|wc
126 585 4874
scraping_courses.sh COMP|grep Soft
COMP1531 Software Engineering Fundamentals
COMP2041 Software Construction: Techniques and Tools
COMP3141 Software System Design and Implementation
COMP3431 Robotic Software Architecture
COMP4161 Advanced Topics in Software Verification
COMP4181 Language-based Software Safety
COMP6447 System and Software Security Assessment
COMP9041 Software Construction: Techniques and Tools
COMP9181 Language-based Software Safety COMP9322 Software Service Design and Engineering
COMP9323 Software as a Service Project COMP9431 Robotic Software Architecture scraping_courses.sh MINE|grep Rock
MINE3630 Rock Breakage
MINE8640 Geotechnical Hazards in Hard Rock Mines
MINE8660 Geotechnical Engineering for Underground Hard Rock
Your script must download the handbook web pages and extract the information from them when it is run.
Hints
This task can be done using the usual tools of egrep, sed, sort & uniq but the regular expressions take some thought.
The UNSW handbook uses seperate web pages for undergraduate and postgraduate courses. These two web pages would need to be downloaded for the above example (OPTM):
http://legacy.handbook.unsw.edu.au/vbook2018/brCoursesByAtoZ.jsp?StudyLevel=Undergraduate&descr=O and http://legacy.handbook.unsw.edu.au/vbook2018/brCoursesByAtoZ.jsp?StudyLevel=Postgraduate&descr=O. Make sure courses which occur in both postgraduate & undergraduate handbooks aren't repeated. cat -A can be useful to check for non-printing characters.
The command curl will download a URL and print it to standard output.
In a script it is best run as curl --silent so it doesn't print extra information on standard error.
For example:
curl --silent "http://legacy.handbook.unsw.edu.au/vbook2018/brCoursesByAtoZ.jsp?
StudyLevel=Undergraduate&descr=O"|grep OPTM
<TD class="" align="left">OPTM2111</TD>
<TD class="evenTableCell" align="left">OPTM2133</TD>
<TD class="evenTableCell"><A
<TD class="" align="left">OPTM2190</TD>
<TD class=""><A
<TD class="evenTableCell" align="left">OPTM2211</TD>
The program wget can be used for the same purpose, by running it as wget -q -O- url
When you think your program is working, you can use autotest to run some simple automated tests:
$ 2041 autotest scraping_courses
Autotest Results
82% of 190 students who have autotested scraping_courses.sh so far, passed all autotest tests. 91% passed test 1
84% passed test 2
87% passed test 3
88% passed test 4
86% passed test 5
When you are finished working on this exercise, you must submit your work by running give:
$ give cs2041 lab02_scraping_courses scraping_courses.sh


When you are finished each exercises make sure you submit your work by running give.
You can run give multiple times. Only your last submission will be marked.
Don't submit any exercises you haven't attempted.
You check the files you have submitted here.
After automarking is run by the lecturer you can view your results here. The resulting mark will also be available via give's web interface.
Lab Marks
When all components of a lab are automarked you should be able to view the the marks via give's web interface or by running this command on a CSE machine:
$ 2041 classrun -sturec

For all enquiries, please email the class account at cs2041@cse.unsw.edu.au
CRICOS Provider 00098G