carbon: script control external monitor control

nix/custom/xbrightness.nix

@@ -0,0 +1,16 @@
+{
+  writeShellApplication,
+
+  bc,
+}:
+
+writeShellApplication {
+  name = "xbrightness";
+  runtimeInputs = [ bc ];
+  text = ''
+    device=$1
+    rel=$2
+    brightness=$(xrandr --verbose | grep Brightness | cut -d':' -f 2)
+    xrandr --output "$device" --brightness "$(echo "$brightness $rel" | bc -l)"
+  '';
+}