Tim Kientzle wrote:
If you really believe that sending output to /dev/null should not do anything, make it a fatal error so people won't rely on it.
That would be silly, as it defeats the whole point of having a /dev/null for output.
At this point we're arguing only about theory, since GNU tar actually does read the files in this case. But in other cases, programs avoid input as an optimization, and that's perfectly all right. For example, 'diff FOO FOO' doesn't read FOO twice, and there's nothing wrong with that. (In fact, 'diff' doesn't read FOO even once.) If GNU tar improved its performance in similar cases, there would be nothing wrong with that either.
It sounds like enough people are misusing GNU tar in the way you describe that, if we improved its performance in this case, we'd need to add a --be-stupid option so that tar would continue to read data that it doesn't need to. (Perhaps you could come up with a better name for the option. :-)
