title: how to find the implementation of a function in linux?
body: <p>Sometimes, I want to know the implementation of a c function. My editor is vim. I have try ctags and cscope, and man.</p>
  
  <p>man 2|3 only tell me how to use a function. </p>
  
  <p>Both ctags and cscope can just find some of the implementation of functions.</p>
  
  <p>They all can't find some functions. especially some system function(calls). </p>
  
  <p>If a function can be use by include some header file, is there any way easily find the implementation of a function,</p>