You should store the result in a variable like this:
result=$((operand1+operand2))
Then your first if
statement can check if this variable has a value, and if it does, skip the read
and use it instead.
if [[ $result == "" ]]; then
echo Enter operand1 value:
read operand1
else
operand1=$result
echo "Operand 1 is: $result"
echo ""
fi
...
Here is the working version of your code:
#!/bin/bash
while true
do
if [[ $# -eq 0 ]] ; then
if [[ $result == "" ]]; then # check if $result is empty
echo Enter operand1 value:
read operand1
else
operand1=$result # if not empty then assign its value to $operand1
echo "Operand 1 is: $result"
echo ""
fi
# Offer choices
echo 1. Addition
echo 2. Subtraction
echo 3. Multiplication
echo 4. Division
echo 5. Exit
echo Enter your choice:
read choice
if [[ $choice != 1 && $choice != 2 && $choice != 3 && $choice != 4 && $choice != 5 ]] ; then
echo Sorry $choice is not a valid operator - please try again
echo Enter your choice:
read choice
fi
echo Enter operand2 value:
read operand2
# get operands and start computing based on the user's choice
if [[ $choice -eq 1 ]] ; then
result=$((operand1+operand2)) # store result
echo ----------------------------------------
echo Addition of $operand1 and $operand2 is $((operand1+operand2))
echo ----------------------------------------
echo
elif [[ $choice -eq 2 ]] ; then
result=$((operand1-operand2)) # store result
echo ----------------------------------------
echo Subtraction of $operand1 and $operand2 is $((operand1-operand2))
echo ----------------------------------------
echo
elif [[ $choice -eq 3 ]] ; then
result=$((operand1*operand2)) # store result
echo ----------------------------------------
echo Multiplication of $operand1 and $operand2 is $((operand1*operand2))
echo ----------------------------------------
echo
elif [[ $choice -eq 4 && operand2 -eq 0 ]] ; then
echo Can not divide by 0 please try again
echo Please enter operand2
read operand2
echo ----------------------------------------
echo Division of $operand1 and $operand2 is $((operand1/operand2))
echo ----------------------------------------
echo
result=$((operand1/operand2)) # store result
elif [[ $choice -eq 4 && operand2 -ne 0 ]] ; then
result=$((operand1/operand2)) # store result
echo ----------------------------------------
echo Division of $operand1 and $operand2 is $((operand1/operand2))
echo ----------------------------------------
echo
elif [[ $choice -eq 5 ]] ; then
exit
else
echo ----------------------------------------
echo Invalid choice.. Please try again
echo ----------------------------------------
echo
fi
else
echo ----------------------------------------
echo You either passed too many parameters or too less
echo than the optimum requirement.
echo
echo This program accepts a maximum of 2 arguments or no
echo argument at all in order to run successfully.
echo ----------------------------------------
fi
done
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