diff --git a/glue/src/screenshot b/glue/src/screenshot
index d056aea..dbcbdde 100755
--- a/glue/src/screenshot
+++ b/glue/src/screenshot
@@ -1,35 +1,58 @@
 #!/bin/sh
 
-if ! type scrot > /dev/null; then
-	>&2 echo "!!! scrot is not installed"
-	exit 1
-fi
+name=`basename "$0"`
+
+isInstalled() {
+	type "$1" > /dev/null
+}
+
+mustHaveInstalled() {
+	if ! isInstalled "$1"; then
+		echo "$name: $1 is not installed" >&2
+		exit 1
+	fi
+}
+
+usage() {
+	echo "Usage: $name [selection | window | screen] [clipboard]" >&2
+	exit 2
+}
 
 picturesDir=`xdg-user-dir PICTURES`
 test -z "$picturesDir" && picturesDir="$HOME/Pictures"
 picturesDir="$picturesDir/Screen Shots"
 
 if ! mkdir -p "$picturesDir"; then
-	>&2 echo "!!! can't create $picturesDir"
+	echo "$name: can't create $picturesDir" >&2
 	exit 1
 fi
-output="$picturesDir/`date -Iseconds`.png"
+outputFilePath="$picturesDir/`date -Iseconds`.png"
 
+mustHaveInstalled scrot
 case "$1" in
-"selection")
-	scrot --select --line style=dash --freeze --file "$output"
-	clipArg="$2"
-	;;
-"window")
-	scrot --focused --border --file "$output"
-	clipArg="$2"
+"selection" | "window" | "screen")
+	mode="$1"
+	shift 1
 	;;
 *)
-	scrot --file "$output"
-	clipArg="$1"
+	mode="screen"
 	;;
 esac
 
-if test "$clipArg" = "clipboard"; then
-	xclip -selection clipboard -target image/png -i "$output"
+if [ "$1" = "clipboard" ]; then
+	clipboard=true
+	shift 1
+fi
+
+[ "$#" -gt 0 ] && usage
+
+case "$mode" in
+"selection") scrot --select --line style=dash --freeze --file "$output";;
+"window"   ) scrot --focused --border --file "$output";;
+"screen"   ) scrot --file "$output";;
+esac
+
+if [ -n "$copyToClipboard" ]; then
+	mustHaveInstalled xclip
+	xclip -selection clipboard -target image/png -i "$outputFilePath"
 fi