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Tutorial12: Shell Scripting - Part 2

12 bytes added, 08:18, 18 March 2021

→‎INVESTIGATION 2: ADDITIONAL LOOPING STATEMENTS

# Run your shell script by issuing: ./if-5.bash When prompted, enter a '''letter''' instead of a ''number''. What happens? Let's edit the '''for-5.bash''' shell script to perform '''error-checking''' to force the user to enter a numeric value between 0 and 100. '''NOTE:''' The '''while''' statement can be used with the '''test''' command (or a simple linux command or a linux pipeline command) for error checking. In our case, we will use a pipeline command with extended regular expressions. In order to loop while the result is TRUE (not FALSE), you can use the negation symbol (!) to set the test condition to the opposite.

# Use a text editor like vi or nano to edit 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.

# Add the following lines in your shell script IMMEDIATELY AFTER the read statement to prompt the user for a mark: while ! echo $mark | egrep "^[0-9]{1,}$" > /dev/null 2> /dev/null do    read -p "Not a valid number. Enter a mark (0-100): " mark done

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

# Run your shell script by issuing: ./for-5.bash

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Tutorial12: Shell Scripting - Part 2

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