getopts Unix input

Question

so in my code below I'm like trying to get my code to read the input that the user enters in my code as seen below

#./MyProject -a -b OR -b -a

However I keep getting a Syntax error and its not passing the tests given by the program: The following tests are: having inputs that aren't a&b (i.e c-z), having no inputs at all, having too little arguments, having too many arguments,

#Use just prints out the format like this : ./MyProject -a -b

 - if ( ! getopts ":ab" arg) then  
echo $use  
fi 

 while [getopts ":ab" arg2] 
do
         case $arg2 in

        t) if (($1 != "t" && $1 != "o")); then
         echo $use 
     fi   
 esac   
done  
}

Answer 1

The following example should work for you.

#!/bin/bash

usage() {
    echo "Usage: $0 -a -b"
    exit
}

while getopts ":a:b:" arg; do
    case $arg in
        a)
            a=${OPTARG}
            (($a == "t" || $a == "o")) || usage
            ;;
        b)
            b=${OPTARG}
            ;;
        *)
            usage
            ;;
    esac
done

echo $a
echo $b