usr/lib/learn/editor/L20.1a

#print
You can now change a line of a file, using only the
commands already taught, by deleting the old line
and inserting a new one.
This is not a very convenient way to do that, so
there is a command 'c' (change) which combines
those operations.
  5c
  input text
  here.
  .
will delete line 5 and replace it by the lines

input text
here.

Note that the text following 'c', just like the text
after 'i' and 'a', must end with a line containing just
one '.' and nothing else.
This directory contains a file named 'short'
with six lines in it.  Change the last line to read

new version of last line

and rewrite the file; then end with "ready".
#create Ref
This is a short file
which contains exactly
six lines of text
of which you are
to change the last line
new version of last line
#create short
This is a short file
which contains exactly
six lines of text
of which you are
to change the last line
this is the last line.
#pipe
#user
#unpipe
#cmp Ref short
#log
#next
21.1a 10