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Tutorial12: Shell Scripting - Part 2

203 bytes removed, 09:51, 5 September 2020

→‎INVESTIGATION 1: ADDITIONAL LOGIC STATEMENTS

# Save your editing session and exit the text editor (eg. with vi: press '''ESC''', then type ''':wx''' followed by '''ENTER''').

# Issue the following linux command to add execute permissions for your shell script: chmod u+x if-3.bash

# Run your shell script by issuing: ./if-3.bash What do you notice? Try running the script several times with numbers different and equal to each other to confirm that the shell script works correctly. It would be nice to have a separate result of the numbers are equal to each other. In order to achieve this, you can use an '''if-elif-else'''~~-else~~ statement.

# Use a text editor like vi or nano to create the text file called '''if-4.bash''' (eg. vi if-4.bash) If you are using the nano text editor, refer to notes on text editing in a previous week in the course schedule.

# Enter the following lines in your shell script: #!/bin/bash clear read -p "Enter the first number: " num1 read -p "Enter the second number: " num2 if [ $num1 -gt $num2 ] then    echo "The first number is greater than the second number." elif [ $num1 -lt $num2 ] then    echo "The first number is less than the second number." else    echo "The first number is equal to the second number." fi # Save your editing session and exit the text editor (eg. with vi: press '''ESC''', then type ''':wx''' followed by '''ENTER'''). NOTE: You should notice in this control-flow statement differs from an if-else statement since if the first condition is FALSE, it is tested again, which can produce two different actions depending if the second test is TRUE or FALSE.

# Issue the following linux command to add execute permissions for your shell script: chmod u+x if-4.bash

# Run your shell script by issuing: ./if-4.bash What do you notice? Try running the script several times with numbers different and equal to each other to confirm that the shell script works correctly. A classic shell script to demonstrate many different paths or actions to take depending of multiple testing using an '''if-elif-else''' statement would be a mark to letter grade converter.

# Use a text editor like vi or nano to create the text file called '''if-5.bash''' (eg. vi if-5.bash) If you are using the nano text editor, refer to notes on text editing in a previous week in the course schedule.

# Enter the following lines in your shell script: #!/bin/bash clear read -p "Enter a mark (0-100): " mark if [ $mark -ge 80 ] then    echo "You receive an A grade." elif [ $mark -ge 70 ] then    echo "The receive a B grade." elif [ $mark -ge 60 ] then    echo "The receive a C grade." elif [ $mark -ge 50 ] then    echo "The receive a D grade." else    echo "You receive an F grade." fi

# Save your editing session and exit the text editor (eg. with vi: press '''ESC''', then type ''':wx''' followed by '''ENTER''').

# Issue the following linux command to add execute permissions for your shell script: chmod u+x if-5.bash

# Run your shell script by issuing: ./if-5.bash What do you notice? Run several times to confirm that the shell script runs correctly for all mark (grade) categories.

:In the next investigation, you will learn more about the '''for''' loop and learn how to use the '''while''' loop for '''error-checking'''.

=INVESTIGATION 2: ADDITIONAL LOOPING STATEMENTS =

Msaul

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Tutorial12: Shell Scripting - Part 2

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