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 Scripts), 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 Two Sample Input Files, 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!