The RCS output format is designed specifically for use by the Revision Control System, which is a set of free programs used for organizing different versions and systems of files. Use the --rcs (-n) option to select this output format. It is like the forward ed format (see Forward ed), but it can represent arbitrary changes to the contents of a file because it avoids the forward ed format's problems with lines consisting of a single period and with incomplete lines. Instead of ending text sections with a line consisting of a single period, each command specifies the number of lines it affects; a combination of the ‘a’ and ‘d’ commands are used instead of ‘c’. Also, if the second file ends in a changed incomplete line, then the output also ends in an incomplete line.
Here is the output of ‘diff -n lao tzu’ (see Sample diff Input, for the complete contents of the two files):
d1 2
d4 1
a4 2
The named is the mother of all things.
a11 3
They both may be called deep and profound.
Deeper and more profound,
The door of all subtleties!