On 12/12/2011 05:50 AM, Kamil Dudka wrote: > Hi, > > the following upstream commit introduces a major change in behavior of du > when multiple arguments are specified: > > http://git.savannah.gnu.org/cgit/coreutils.git/commit/?id=efe53cc > > ... and the issue has landed as a bug in our Bugzilla: > > https://bugzilla.redhat.com/747075#c3 > > Was such a change in behavior intended?
A change in behavior was intended, but I think we ended up introducing a bug in its place. > The info > documentation states: > > The FILE argument order affects which links are counted, and changing the > argument order may change the numbers that `du' outputs. And this is intended. The end goal is that if a directory appears both on the command line and as a child of another directory on the command line, that it gets counted only once. > > However, changing the numbers is one thing and missing lines in the output > of du is quite another thing. Yes, that's the bug I think we introduced - we are mistakenly eliding lines of output, rather than listing those directories with 0 attributed additional size. More importantly, POSIX says of -s: "−s Instead of the default output, report only the total sum for each of the specified files." But we fail that: $ mkdir -p /tmp/a/b $ cd /tmp/a $ du -s . b 8 . $ du -s b . 4 b 4 . We correctly deduced that only 8 units were occupied (that is, b was not double-counted in either approach), but we _failed_ to list b in the first approach. I think POSIX requires the output to have been: $ du -s . b 8 . 0 b as an indication that we did visit b, but that there were no additional contributions to the disk usage encountered during our visit there. Meanwhile, without -s, I still think we elided too much data: $ du . b 4 ./b 8 . $ du b . 4 b 4 . In the first case, we recursed into ./b, then back out to ., but elided any notion that we ever directly visited b. In the second case, we visited b, then recursed into ./b but had nothing to output, then back out to '.'. I think that a saner output would be: $ du . b 4 ./b 8 . 0 b $ du b . 4 b 0 ./b 4 . to make it obvious that we pruned recursion at points where we encountered duplicates, and that the sum of the first columns shows an accurate disk usage. -- Eric Blake ebl...@redhat.com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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