Week 09 Tutorial Questions

Objectives

  1. Below are the current assignment autotests.

    Discuss what these print and why:

    subset 0: quit
        seq 42 44 | 2041 eddy 1q

        2041 eddy 10q < dictionary.txt

        seq 41 43 | 2041 eddy 4q

        seq 90 110 | 2041 eddy /.1/q

        2041 eddy '/r.*v/q' < dictionary.txt

        yes | 2041 eddy 3q
    subset 0: print
        seq 41 43 | 2041 eddy 2p

        head dictionary.txt | 2041 eddy 3p

        seq 41 43 | 2041 eddy -n 2p

        2041 eddy -n 42p < dictionary.txt

        head -n 1000 dictionary.txt | 2041 eddy -n '/z.$/p'
    subset 0: substitute
        seq 1 5 | 2041 eddy 's/[15]/zzz/'

        seq 1 5 | 2041 eddy 's/[15]/zzz/g'

        echo "Hello Andrew" | 2041 eddy 's/e//'

        echo "Hello Andrew" | 2041 eddy 's/e//g'
    subset 1: addresses
        seq 1 5 | 2041 eddy '$d'

        seq 42 44 | 2041 eddy 2,3d

        seq 10 21 | 2041 eddy 3,/2/d

        seq 10 21 | 2041 eddy /2/,7d

        seq 10 21 | 2041 eddy /2/,/7/d
    subset 1: substitute
        seq 1 5 | 2041 eddy 'sX[15]XzzzX'
    subset 1: multiple commands
        seq 1 5 | 2041 eddy '4q;/2/d'
    subset 1: -f
        echo "4q" > commands.script
    echo "/2/d" >> commands.script
    seq 1 5 | 2041 eddy -f commands.script
    subset 1: input files
        seq 1 2 > two.txt
    seq 1 5 > five.txt
    2041 eddy '4q;/2/d' two.txt five.txt
    subset 1: whitespace
        seq 24 42 | 2041 eddy ' 3, 17  d  # comment'
    subset 2: -i
        seq 1 5 > five.txt
    2041 eddy -i /[24]/d five.txt
    cat five.txt
    subset 2: multiple commands
        echo 'Punctuation characters include . , ; :' | 2041 eddy 's/;/semicolon/g;/;/q'

  2. Write a Python program, tags.py which given the URL of a web page fetches it by running wget(1) and prints the HTML tags it uses.

    The tag should be converted to lower case and printed in alphabetical order with a count of how often each is used.

    Don't count closing tags.

    Make sure you don't print tags within HTML comments. 

        ./tags.py https://www.cse.unsw.edu.au
    a 141
    body 1
    br 14
    div 161
    em 3
    footer 1
    form 1
    h2 2
    h4 3
    h5 3
    head 1
    header 1
    hr 3
    html 1
    img 12
    input 5
    li 99
    link 3
    meta 4
    noscript 1
    p 18
    script 14
    small 3
    span 3
    strong 4
    title 1
    ul 25

    Note the counts in the above example will not be current - the CSE pages change almost daily.

  3. Add an -f option to tags.py which indicates the tags are to be printed in order of frequency. 

        ./tags.py -f https://www.cse.unsw.edu.au
    head 1
    noscript 1
    html 1
    form 1
    title 1
    footer 1
    header 1
    body 1
    h2 2
    hr 3
    h4 3
    span 3
    link 3
    small 3
    h5 3
    em 3
    meta 4
    strong 4
    input 5
    img 12
    br 14
    script 14
    p 18
    ul 25
    li 99
    a 141
    div 161

  4. Modify tags.py to use the requests and beautifulsoup4 modules.

  5. If you fell like a harder challenge after finishing the challenge activity in the lab this week have a look at the following websites for some problems to solve using regexp: