I built opencv-2.4.13 in linux.but i made changes in code in cpp included in modules.would it rquire to rebuild the entire opencv code or that modified file?and how is it possible to built that modified file

edit

yes, you have to rebuild the library.

you can try to shortcut by:

make opencv_something

and hope, that it will only rebuild that specific module & it's dependancies, but that's only good while actually working on that module, in the end, you have to use:

make install

(which will rebuild a lot, if not all modules)