Linux:diff

diff - find differences between two files

diff options

       -p     Show which C function each change is in.
       -r     When comparing directories, recursively compare any subdirectories found.
       -u     Use the unified output format.

Creating a patch for a single file

diff -up original.file new.file > filename.diff

Creating a patch for directory

diff -urp original_directory new_directory > filename.diff