File «» it’s the original program, and «» it´s the original program fixed (Other version):

whit «diff» comand,  we compare the two files, and save in «disk_usage.diff» :

diff -u > disk_usage.diff

The «disk_usage.diff» file contend the differences between the files.

When we will apply the changes, usa the «patch» command:

patch < disk_usage.diff

We can see the program file original has been modified.