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Hi I am doing a project where I must write a bash script calculator that allows you to perform multiple arithmetic operations and also to the power of. I have done the basic bit but have been told I must make it non interactive and was just wondering how would I do this? My code has been provided below.

clear
bash
while [ -z "$arg1" ]
do
read -p "Enter argument1: " arg1
done

while [ -z "$arg2" ]
do
read -p "Enter argument2: " arg2
done

echo "You've entered: arg1=$arg1 and arg2=$arg2"

let "addition=arg1+arg2"
let "subtraction=arg1-arg2"
let "multiplication=arg1*arg2"
let "division=arg1 / arg2"
let "power=arg1**arg2"

echo -e "results:\n"
echo "$arg1+$arg2=$addition"
echo "$arg1-$arg2=$subtraction"
echo "$arg1*arg2=$multiplication"
echo "$arg1/$arg2=$division"
echo "$arg1^$arg2=$power"

I was thinking of trying to make it so that the user does not have to type in 2 numbers but I am still pretty new to bash and scripts as a whole so I am wondering how to do this.

Mike 'Pomax' Kamermans
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Joshua
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    Use the command line arguments instead of prompting for input. These are in `$1`, `$2`, etc. – Barmar Feb 03 '23 at 16:43
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    See [How can I pass a command line argument into a shell script?](https://unix.stackexchange.com/q/31414/264812). – pjh Feb 03 '23 at 16:51
  • Also see [Handling positional parameters [Bash Hackers Wiki]](http://wiki.bash-hackers.org/scripting/posparams). – pjh Feb 03 '23 at 17:01

1 Answers1

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Use getopts to process arguments to your script. Here is an example from this site. You could replace the lines from your first line to your echo "You've entered …" with modified code from the other answer I linked to. You might want to read the PARAMETERS section of man bash, in particular understand what the Special Parameters are (*, @, #, ?, -, $, !, and 0). You should know those cold if you are scripting bash.

An alternative is to use the builtin read. I would use getopts.

John
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