Maximizing a window (Keepassx2) from command line

I'm using i3wm and Keepassx2 on an Arch-Linux installation. I configured i3 to automatically move a window with the window class "Keepassx2" to a certain workspace $WSKP. I also configured $mod+P to execute Keepassx2. Now I would like to write a custom script that is executed by $mod+P instead. This script should: - launch Keepassx2 when no other instance of it is currently running - maximize Keepassx2 and move focus to the specific workspace $WSKP when there already is a running instance I want this because I don't need the Keepass-Workspace to be open all the time and it takes another unnecessary keypress when tabbing through the workspaces. Checking whether there already is a running instance is easy: if [ $(pidof keepassx2) ]; then # maximize the running instance and move focus with i3-msg fi; But how do I accomplish maximizing the running instance?