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Tutorial12: Shell Scripting - Part 2

745 bytes added, 14:58, 29 December 2020

→‎INVESTIGATION 2: ADDITIONAL LOOPING STATEMENTS

# Enter the following lines in your shell script: #!/bin/bash value=1 while [ $value -le 5 ] do   echo "$value"   value=value+1 done

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

# Set execute permissions for this shell script and run your shell script by issuing: ./for-6.bash What do you notice? You should have noticed an error message. ~~In our lesson~~# To demonstrate what went wrong, ~~we mentioned~~ issue the following commands: num1=5;num2=10 result=$num1+$num2 echo $result Notice that ~~values in~~ the user-defined ~~variables are stored as '''TEXT'''~~variable stores the text "10+5" which is NOT the expected result of adding the number 10 and 5. ~~Therefore~~ As you may recall in class, we need to convert a number stored as text into a '''binary number''' for calculations (in this case, advance the value by 1 for each loop). We can accomplish this by either using the expr command, or by surrounding our math operation within a set of two round brackets. # To demonstrate, issue the following set of commands: num1=5;num2=10 result=$( expr $num1+$num2) echo $result ((result=$num1+$num2)) echo $result Let's apply this technique we just learned to correct our recently created shell script.

# Use a text editor like vi or nano to edit the text file called '''for-6.bash''' (eg. vi for-6.bash) If you are using the nano text editor, refer to notes on text editing in a previous week in the course schedule.

# Change line 6 to the following: ((value=value+1))

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Tutorial12: Shell Scripting - Part 2

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