Minor performance improvements (#975)

* Skip head and grep and do it all in sed

* Replace echo and awk with a parameter expansion

.local/bin/compiler

@@ -53,5 +53,5 @@ case "$ext" in
 	scad) openscad -o "$base".stl "$file" ;;
 	sent) setsid -f sent "$file" 2>/dev/null ;;
 	tex) textype "$file" ;;
-	*) head -n1 "$file" | grep "^#!/" | sed "s/^#!//" | xargs -r -I % "$file" ;;
+	*) sed -n '/^#!/s/^#!//p; q' "$file" | xargs -r -I % "$file" ;;
 esac