CPP defines...

[News reading a/c for rb]

Here's a nasty little script that comes in useful when you
want to know what your cpp *really* predefines: we have found
that the man page is sometimes economical with the truth.
Those of you without strings(1) and/or a separate /lib/cpp will
have to use your imagination.
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#!/bin/sh
strings -a -2 /lib/cpp | sed '/^a-zA-Z0-9_/!s/.*/#ifdef &\
"%&"\
#endif/p' |/lib/cpp |sed -n '/%/s/[%"]//gp'