add help/options

pizza.sh

@@ -1,9 +1,31 @@
 #!/usr/bin/env bash
+FSI=2.12206590789 # grams of Flour per Square Inch of pan
 
-FSI=2.12206590789 # grams of flour per square inch of pan
+function pizzahelp {
+	echo "Pizza Calculator: The pizza script you never asked for"
+	echo
+	echo "Usage: ./pizza.sh [-h] [-f] [<flour weight>g|<pan diameter>(in|inch|\")]"
+	echo "Options:"
+	echo "	-h	Print this help"
+	echo "	-f <N>	Set flour per square inch"
+	echo
+}
+
+while getopts ":hf:" option; do
+	case $option in
+		h)
+			pizzahelp
+			exit;;
+		f)
+			FSI=$OPTARG
+			shift 2;;
+		\?)
+			echo "Error: Invalid option"
+			exit;;
+	esac
+done
 
 function panarea {
-	read -p "Diameter of pan (in inches): " DIAM
 	AREA=$(echo "3.1415926535*($DIAM/2)^2" | bc)
 	SIZE=$(echo $AREA*$FSI | bc)
 	calcratio
@@ -19,4 +41,20 @@ function calcratio {
 	done
 }
 
-panarea
+case $1 in
+	*g)
+		SIZE=$(echo $1 | sed s/g//g)
+		calcratio;;
+	*\")
+		DIAM=$(echo $1 | sed s/\"//g)
+		panarea;;
+	*inch)
+		DIAM=$(echo $1 | sed s/inch//g)
+		panarea;;
+	*in)
+		DIAM=$(echo $1 | sed s/in//g)
+		panarea;;
+	*)
+		read -p "Diameter of pan (in inches): " DIAM
+		panarea;;
+esac