Check if Gazebo simulation is running

is_simulation_running.py

#!/usr/bin/env python

from time import sleep
import rospy


if __name__ == '__main__':
    rospy.init_node('check_time')
    # Until rospy initalizes the time returned will be 0
    # so we need to give a bit of time to see if it initializes
    sleep(2)
    if rospy.Time.now() == rospy.Time():
        print "Simulation stalled/paused"
    else:
        print "Simulation running correctly"