Counting calculation operations and writing them into a file from a shell script

Question

guys. I'm new to Linux and shell scripting in general and I have a question.

I have the following simple calculator:

input="yes"
while [[ $input = "yes" ]]
do

    PS3="Press 1 for Addition, 2 for subtraction, 3 for multiplication and 4 for division: "
    select math in Addition Subtraction Multiplication Division
    do
        case "$math" in
        Addition)
            echo "Enter first no:"
            read num1
            echo "Enter second no:"
            read num2
            result=`expr $num1 + $num2`
            COUNTER=COUNTER+1 
            echo Answer: $result
            break
        ;;
        Subtraction)
            echo "Enter first no:"
            read num1
            echo "Enter second no:"
            read num2
            result=`expr $num1 - $num2`
            echo Answer: $result
            break
        ;;
        Multiplication)
            echo "Enter first no:"
            read num1
            echo "Enter second no:"
            read num2
            result=`expr $num1 * $num2`
            echo Answer: $result
            break
        ;;
        Division)
            echo "Enter first no:"
            read num1
            echo "Enter second no:"
            read num2
            result=$(expr "scale=2; $num1/$num2" | bc)
            echo Answer = $result
            break
        ;;
        *)
            echo Choose 1 to 4 only!!!!
            break
        ;;
    esac
    done

done

All I want is to be able to count the operations (meaning that for a successfull operation is +1, like "2 + 5 = 7" and some counter variable goes +1.. then something else and again +1) untill the user types something to stop the calculator. Then the counter variable (which holds the total number of operations performed) should be written inside a new file. How can I do this or can someone give me an example?

Answer 1

You can use a counter:

• set count=0 before the loop
• increment the counter after successful operation with ((count++)) after checking the status ( $? ) of the arithmetic operation
• write the count to a file with printf "%d\\n" "$count" > file

Not sure why you want to write to a new file each time. If that is the desired behavior, you can generate a new filename each time. Probably, you could name your file as operation.txt.N where N is the counter.

You can add Quit as an option that user can select:

PS3="Press 1 for Addition, 2 for subtraction, 3 for multiplication, 4 for division and 5 to Quit: "
select math in Addition Subtraction Multiplication Division Quit
... existing code here ...

And add this case:

    Quit)
        input=no
        break
    ;;