the present perfect continuous

We use the present perfect
continuous to talk about an action or actions that started in the past
and continued until recently or continues into the future.

Sometimes it refers to an action that has finished but where you can still see evidence.

• 
  You look tired. Have you been sleeping properly?
  
• 
  I can smell smoke. Has somebody been smoking?
  
• 
  I've got a headache and a stiff neck. I've been working too long on computer.
  

Sometimes it refers to an action that has not finished.

• 
  I've been waiting for him for 30 minutes and he still hasn't arrived.
  
• 
  I've been learning English for 20 years and I still don't know very much.
  
• 
  He's been asking me about it for days. I wish he would stop.
  

Sometimes it refers to a series of actions.

• 
  He's been phoning me all week for an answer.
  
• 
  I've been writing to her regularly for a couple of years.
  
• 
  The company has been sending students here for over twenty years.
  

Typical time expression
that are used with the present perfect continuous include 'since',
'for', 'all week', 'for days', 'lately', 'recently', 'over the last few
months'.

• 
  He's been working here since 2001.
  
• 
  I've been wanting to do that for ten years.
  
• 
  They haven't been answering all week.
  
• 
  She hasn't been talking to me for days.
  
• 
  I've been working hard lately.
  
• 
  We've been looking at other options recently.
  
• 
  You haven't been performing well over the last few months