updated ruby_gem_install_if_absent.sh

ruby_gem_install_if_absent.sh

@@ -32,29 +32,40 @@ usage(){
     exit 3
 }
 
+for arg; do
+    case "$arg" in
+        -*) usage
+            ;;
+    esac
+done
+
 gems=""
-for x in "$@"; do
+
-    if [ -f "$x" ]; then
+process_args(){
-        echo "adding gems from file:  $x"
+    for arg; do
-        gems="$gems $(sed 's/#.*//;/^[[:space:]]*$$/d' "$x")"
+        if [ -f "$arg" ]; then
+            echo "adding gems from file:  $arg"
+            gems="$gems $(sed 's/#.*//;/^[[:space:]]*$$/d' "$arg")"
             echo
         else
-        gems="$gems $x"
+            gems="$gems $arg"
         fi
-    gems="$(tr ' ' ' \n' <<< "$gems" | sort -u | tr '\n' ' ')"
     done
+}
 
-for x in "$@"; do
+if [ -n "${*:-}" ]; then
-    case "$1" in
+    process_args "$@"
-        -*) usage
+else
-            ;;
+    # shellcheck disable=SC2046
-    esac
+    process_args $(cat)
-done
+fi
 
 if [ -z "$gems" ]; then
     usage
 fi
 
+gems="$(tr ' ' ' \n' <<< "$gems" | sort -u | tr '\n' ' ')"
+
 echo "Installing Ruby Gems that are not already installed"
 echo