Lab 6: Arithmetic and Find

Questions

1. Write a script which prints a triangle of * characters. The first row should be a single *, the second **, and so on. You can use echo -n to print output without a newline at the end. The number of rows is specified by the command line argument -r. If no argument is provided, print 4 rows.

   > ./triangle.sh -r 1
   *
   
   > ./triangle.sh
   *
   **
   ***
   ****
   
   > ./triangle.sh -r 6
   *
   **
   ***
   ****
   *****
   ******
   

   #!/bin/bash
   
   if [[ $# -gt 1 && $1 -eq '-r' ]]
   then
       size=$2
   else
       size=4
   fi
   
   row=1
   while [[ $row -le $size ]]
   do
       col=1
       while [[ $col -le $row ]]
       do
           echo -n '*'
           col=$((col+1))
       done
       echo
       row=$((row+1))
   done
   

2. Modify your triangle script so that instead of printing *s, it prints a character selected using the rules below:
   • If you are printing the last column, print \
   • Otherwise, if you are printing the first column, print |
   • Otherwise, if the row number is odd, print L
   • Otherwise, print *

   > ./triangle.sh -r 1
   \
   
   > ./triangle.sh
   \
   |\
   |L\
   |**\
   
   > ./triangle.sh -r 6
   \
   |\
   |L\
   |**\
   |LLL\
   |****\
   

   #!/bin/bash
   
   if [[ $# -gt 1 && $1 -eq '-r' ]]
   then
       size=$2
   else
       size=4
   fi
   
   row=1
   while [[ $row -le $size ]]
   do
       col=1
       while [[ $col -le $row ]]
       do
           if [[ $col -eq $row ]]
           then
               echo -n '\'
           elif [[ $col -eq 1 ]]
           then
               echo -n '|'
           elif [[ $((row%2)) -eq 0 ]]
           then
               echo -n 'L'
           else
               echo -n '*'
           fi
   
           col=$((col+1))
       done
       echo
       row=$((row+1))
   done
   

3. Find the file called kangaroo.cow. Hint: start in /usr

find /usr -name kangaroo.cow

4. Fine the directory called mess under /lab

find /lab -name mess -type d

5. Scattered across the subdirectories of mess are 5 scripts with the word lab in their name. Write a find command to make these scripts executable and move them to /lab/week6/safe. Remember that wildcards in find patterns must be quoted, otherwise shell will expand them.

find /lab/week6/mess -type f -name '*'lab'*' -exec chmod +x {} \; -exec cp {} /lab/week6/safe \;

Bonus

1. Modify triangle.sh to support command-line arguments for additional functionality:

   --bottom -b Print a line of dashes (-) beneath the triangle to form a bottom edge
   
   --rows, -r=ROWS Number of rows to print (default 4)
   
   --character, -c=CHAR Use CHAR in place of * when printing. You may assume CHAR is a single-character string
   
   --help, -h Display this help message and exit
   

Department of Computer Science & Software Engineering The University of Western Australia Last modified: 8 February 2022 Modified By: Daniel Smith