Apply diff to a file
 

After I do a diff between two files, how to apply the result to a file so that it is updated by the result?

e.g. diff filev1 filev2 > result
I want to use the result to modify a file (filev3) so that it contains the latest difference?

After creating the patch with, for example "diff -u" you apply it with the "patch" command. For example:

diff -u filev1 filev2 > result

To then turn file1 into file2, use:

patch < result