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Tutorial10: Shell Scripting - Part 1

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# Use a text editor like vi or nano to create the text file called '''if-1.bash''' (eg. vi if-1.bash)

# Enter the following lines in your shell script: #!/bin/bash num1=5 num2=10 if [ $num1 -lt $num2 ] then    echo "num1 is less than num2" fi

# Save your editing session and exit the text editor (eg. with vi: press '''ESC''', then type ''':wxx''' followed by '''ENTER'''). [[Image:if-1.png|thumb|right|200px|Output of a shell script using the '''if''' control-flow statement.]]

# Issue the following Linux command to add execute permissions for your shell script: chmod u+x if-1.bash

# Run your shell script by issuing: ./if-1.bash Confirm that the output indicates a correct result.

# Use a text editor like vi or nano to create the text file called '''if-2.bash''' (eg. vi if-2.bash)

# Enter the following lines in your shell script: #!/bin/bash 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." fi

# Save your editing session and exit the text editor (eg. with vi: press '''ESC''', then type ''':wxx''' followed by '''ENTER'''). [[Image:if-2.png|thumb|right|320px|Output of a shell script using the '''read''' command and the '''if''' control-flow statement.]]

# Issue the following Linux command to add execute permissions for your shell script: chmod u+x if-2.bash

# Run your shell script by issuing: ./if-2.bash When prompted, make certain that the '''first number''' is greater than the '''second number'''. What happens?

# Use a text editor like vi or nano to create the text file called '''if-3.bash''' (eg. vi if-3.bash)

# Enter the following lines in your shell script: #!/bin/bash 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." else    echo "The first number is less than or equal to the second number." fi [[Image:if-3.png|thumb|right|330px|Output of a shell script using the '''if-else''' control-flow statement.]]

# Save your editing session and exit the text editor (eg. with vi: press '''ESC''', then type ''':wxx''' 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 Try running the script several times with numbers '''different''' and '''equal''' to each other to confirm that the shell script works correctly. '''LOOP STATEMENTS''' are a series of steps or sequence of statements executed repeatedly zero or more times satisfying the given condition is satisfied.'' Reference: https://www.chegg.com/homework-help/definitions/loop-statement-3 There are several loops, but we will look at a '''for''' loop using a '''list'''.

# Use a text editor like vi or nano to create the text file called '''for-1.bash''' (eg. vi for-1.bash)

# Enter the following lines in your shell script: #!/bin/bash echo for x in 5 4 3 2 1 do    echo $x done echo "blast-off!" echo

# Save your editing session and exit the text editor (eg. with vi: press '''ESC''', then type ''':wxx''' followed by '''ENTER'''). [[Image:for-1.png|thumb|right|125px|Output of a shell script using the '''for''' loop with a '''list'''.]]

# Issue the following Linux command to add execute permissions for your shell script: chmod u+x for-1.bash

# Run your shell script by issuing: ./for-1.bash

# Use a text editor like vi or nano to create the text file called '''for-2.bash''' (eg. vi for-2.bash)

# Enter the following lines in your shell script: #!/bin/bash echo for x do    echo $x done echo "blast-off!" echo

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

# Issue the following Linux command to add execute permissions for your shell script: chmod u+x for-2.bash [[Image:for-2.png|thumb|right|175px|Output of a shell script using the '''for''' loop without a '''list'''.]]

# Run your shell script by issuing: ./for-2.bash 10 9 8 7 6 5 4 3 2 1 How does this differ from the previous shell script? You will learn in a couple of weeks more examples of using loop statements. Let's run a '''checking-script''' to confirm that both your '''for-1.bash''' and '''for-2.bash'''

Msaul

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Tutorial10: Shell Scripting - Part 1

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