# Changes

## Tutorial10: Shell Scripting - Part 1

, 11 March
INVESTIGATION 3: COMMAND SUBSTITUTION / MATH OPERATIONS
# Issue the following Linux commands demonstrating other types of math calculations:<br><span style="color:blue;font-family:courier;font-weight:bold">echo "\$((2 - 3))"</span><br><span style="color:blue;font-family:courier;font-weight:bold">echo "\$((2 * 3))"</span><br><span style="color:blue;font-family:courier;font-weight:bold">echo "\$((2 / 3))"</span><br><span style="color:blue;font-family:courier;font-weight:bold">echo "\$((2 ** 3))"</span><br><br>'''NOTE:''' You may notice that '''dividing''' '''2''' by '''3''' shows a '''zero''' result. To perform decimal calculations would require<br>the use the '''awk''' or '''bc''' Linux commands (we will '''NOT''' cover that method to work with ''decimal numbers'' in this course).<br><br>You can use the ''math construct'' with variables as well.<br><br>
# Issue the following Linux commands demonstrating using the ''math construct'' with '''variables''':<br><span style="color:blue;font-family:courier;font-weight:bold">num1=34</span><br><span style="color:blue;font-family:courier;font-weight:bold">num2=12</span><br><span style="color:blue;font-family:courier;font-weight:bold">echo "\$((num1 * num2))"</span><br><br>What did you notice?<br><br>You can create variables and assign them values in the ''math construct'' as well.<br><br>
# Issue the following Linux commands demonstrating using the math construct with '''variables''':<br><span style="color:blue;font-family:courier;font-weight:bold">num1=5</span><br><span style="color:blue;font-family:courier;font-weight:bold">num2=3</span><br><span style="color:blue;font-family:courier;font-weight:bold">((result = num1 ** num2))</span><br><span style="color:blue;font-family:courier;font-weight:bold">echo "The result is: \$result"</span><br><br>
# Use a text editor to create a Bash shell script called '''dog-years.bash'''<br><br>
# Add the following lines to the beginning of this file:<br><span style="font-family:courier;font-weight:bold;">#!/bin/bash<br>echo<br>dogFactor=7<br>read -p "Please enter your age (in years): " humanYears<br>((dogYears = humanYears * dogFactor))<br>echo "You age in dog-years is: \$dogYears"<br>echo<br></span><br>
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