What is the difference between 赶紧, 连忙 and 赶快? 赶紧, 连忙 and 赶快 (in addition to 马上, 立刻 and 立即) seem to mean 'immediately', 'forthwith'.
However, I don't really understand where their meanings overlap or if they are somehow different in a particular way. Does anyone know?
From what I can ascertain, it would seem that 连忙 is just a synonym of 马上，but 赶紧，赶快 are in a different category of sorts.
赶紧 and 赶快 are more frequently used to command someone to do something. 


  小明，赶紧过来吃饭！
  
  现在已经很晚了，同学们赶快回家吧！


连忙 tends to be used in describing people’s actions. 


  长官一声令下，士兵们便连忙跑到操场集合。