bash: get only double dash or single dash options

In a linux bash script I want to have two lists of arguments, one are those started with single dash and the other those started with double dash

   example -a 1 --b=3 -c 7 --d=8

then it can return them in two group variables

  group1 : -a 1 -c 7
  group2 : --b=3 --d=8

I know that $@ holds a list of all arguments, don’t know whether I should iterate them and make them distinct or there are easier solutions. This is my try:

g1=""
g2=""
for i in $@; do
   echo $i
   if [[ $i == --* ]]; then
      g1="${g1} $i"
   else
      g2="${g2} $i"
   fi 
done
echo $g1
echo $g2

regardless of its accuracy, it says:

test.sh: 5: [[: not found

>Solution :

Use a case/esac to facilitate the option parsing instead of a ìf. And use the shebang (#!) to choose the shell you want to use:

#!/bin/sh

g1=""
g2=""
for i in $@; do
   echo $i
   case $i in
       --*) g1="${g1} $i";;
       *) g2="${g2} $i";;
   esac 
done
echo $g1
echo $g2