root@pve1:~# cp aml-build.c aml-build.c_test
root@pve1:~# ls
aml-build.c aml-build.c_mod aml-build.c_test
root@pve1:~# diff -up aml-build.c aml-build.c_mod > test // patch create
root@pve1:~# patch -Np1 aml-build.c_test < test // patch test
patching file aml-build.c_test
root@pve1:~# diff -up aml-build.c_mod aml-build.c_test > test2 // patch Verify
-rw-r--r-- 1 root root 1801 Mar 16 14:11 test <-- 1801byte
-rw-r--r-- 1 root root 0 Mar 16 14:16 test2 <-- 0byte