How to fix “No newline at end of file” warning for lots of files?

Question

I have a huge number of source files that are all lacking a newline at the end.

How do I automatically add a newline to the end of each of them?

Some may already have a newline, so it should only be added if necessary.

I'm probably not looking for code, per se, but just something I can run in Terminal to add the necessary newlines (or some kind of programming or development tool).

Answer 1

Converted Norman's answer to a split one-liner for convenience.

for i in * ; do  echo $i; \
 if diff /dev/null "$i" | tail -1 | \
  grep '^\\ No newline' > /dev/null; then echo >> "$i"; \
 fi; done

Replace * with whatever file pattern you want, eg *.c

And another to just tell you which files are broken:

for i in * ; do \
 if diff /dev/null "$i" | tail -1 | \
  grep '^\\ No newline' > /dev/null; then  echo $i; \
 fi; done