how does emacs implement grep? -

when emacs grep, can split window , show nice buffer , , emacs has function (grep args),i want know, how can source code?

emacs executes external grep process, , formats output. assuming mean source code wraps , displays it, not grep itself, pretty simple:

m-x find-function <ret> grep <ret>  (find-function function)  find definition of function near point.  finds source file containing definition of function near point (selected `function-called-at-point') in buffer , places point before definition. set mark before moving, if buffer existed. 

you may find find-library useful poke around with.