Check if screen is installed before using it.

chmouel · vishvananda · commit 44b5736d23aa · 2012-02-08T22:05:48.000Z
Fixes 928377

Change-Id: Ie34860e6d08a457dd52a6c3106d63b54c284f6f3
diff --git a/stack.sh b/stack.sh
@@ -90,7 +90,7 @@ source ./stackrc
 DEST=${DEST:-/opt/stack}
 
 # Check to see if we are already running a stack.sh
-if screen -ls | egrep -q "[0-9].stack"; then
+if type -p screen >/dev/null && screen -ls | egrep -q "[0-9].stack"; then
     echo "You are already running a stack.sh session."
     echo "To rejoin this session type 'screen -x stack'."
     echo "To destroy this session, kill the running screen."
