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→INVESTIGATION 2: ADDITIONAL LOOPING STATEMENTS
# Run your shell script by issuing: <span style="color:blue;font-weight:bold;font-family:courier;">./for-5.bash</span><br><br>What do you notice? Does the output for this shell script differ than for-4.bash? Why?<br><br>The last thing in this section is to introduce you to '''error-checking'''.<br><br>
# Use the '''more''' command to view the text file called '''if-5.bash''' (eg. <span style="color:blue;font-weight:bold;font-family:courier;">more if-5.bash</span>)<br><br>Take a few moments to re-familiarize yourself with this shell script<br><br>
# Run your shell script by issuing: <span style="color:blue;font-weight:bold;font-family:courier;">./if-5.bash </span><br><br>When prompted, enter a letter instead of a number. What happens?<br><br>Let's edit the if-5.bash shell script to perform error-checking to force the user to enter a numeric value between 0 and 100.<br><br>'''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.<br><br>
# Use a text editor like vi or nano to edit the text file called '''if-5.bash''' (eg. <span style="color:blue;font-weight:bold;font-family:courier;">vi if-5.bash</span>)<br><br>If you are using the nano text editor, refer to notes on text editing in a previous week in the course schedule.<br><br>
# Add the following lines in your shell script <u>AFTER</u> the read statement to prompt the user for a mark:<br><span style="font-family:courier;"><br>while ! echo $mark | egrep "^[0-9]{1,}$" > /dev/null 2> /dev/null<br>do<br> read -p "Not a valid number. Enter a mark (0-100): " mark<br>done</span><br><br>
