I do not understand what this means. 0a1,4 means

"a" denotes an addition. "d" denotes a deletion. The numbers on the left form a range of line numbers in file1. The numbers on the right form a range of line numbers in file2.

and how to make the output files identical

Some options: 

cp file1 file2

[download]
cp file2 file1

[download]
truncate -s 0 file1 file2

[download]

In reply to Re^3: diff command by ikegami
in thread diff command by bjohn

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