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ed Scripts
diff can produce commands that direct the ed text editor
to change the first file into the second file. Long ago, this was the
only output mode that was suitable for editing one file into another
automatically; today, with patch, it is almost obsolete. Use the
-e or --ed option to select this output format.
Like the normal format (see Normal), this output format does not
show any context; unlike the normal format, it does not include the
information necessary to apply the diff in reverse (to produce the first
file if all you have is the second file and the diff).
If the file d contains the output of diff -e old new, then
the command (cat d && echo w) | ed - old edits old to make
it a copy of new. More generally, if d1, d2,
..., dN contain the outputs of diff -e old new1,
diff -e new1 new2, ..., diff -e newN-1 newN,
respectively, then the command (cat d1 d2 ... dN && echo w) |
ed - old edits old to make it a copy of newN.
