# getting command-line options using shell case statement

num=""
file=""
for i # go through command-line args
do
  #echo "$i"
  case "$i" in
   #-*) num=$(( - i ));;
   -[0-9]|-[0-9][0-9]) num=$(( - i ));;
   -*) echo "bad number $i" 1>&2; exit 1;;
   #default:
    *) file="$file $i";;
  esac
done
echo "num = $num, file = $file"
cat $file # will cat standard input if $file is empty

# sample runs:
# $ dash case.sh -2 j j
# num = 2, file =  j j
# hi
# hi
# $ echo something | dash case.sh -6
# num = 6, file =
# something
# $