> My reading of <http://austingroupbugs.net/view.php?id=527#c1104> > is that POSIX allows but does not require the current GNU behavior, > and that future versions of POSIX may require the current GNU behavior.
Thanks Paul, I agree with your reading of this. Sounds like POSIX allows both the new and old behaviors. I must express, however, that I think this is a case where both the standard and the current implementation were well-intentioned but not well thought out. Please allow me to state some reasons why I am opposed to the current behavior followed by an example. If I fail to persuade people then I will let this issue be. 1. I find it unintuitive that the number in a line of output from du does not necessarily reflect the size of the corresponding directory or file. Without being privy to du's behavior regarding links and multiple command-line arguments, this would be my expectation. 2. Although I can see how it might add functionality to avoid recounting files with a link count greater than one (although I don't find it personally useful) I do not see any added benefit of not recounting files with link count equal to one (e.g., across multiple command-line arguments). This is where I think the implications of the POSIX standard were not well thought out. I think that the intention was to prevent counting files multiple times if there were multiple links to the same file. As an ill-considered side effect of this, and particularly in the current implementation, we now find that du will not recount across multiple command-line arguments. I have an examples of how this is confusing below. 3. I find it surprising that the order of command-line arguments to du may affect the output of du. Users don't expect this. 4. This deviates significantly from other implementations and historical behavior. To my knowledge, gnu-coreutils is the odd-man-out with all other implementations following the previous behavior. 5. I couldn't agree with Bernhard Voelker more: > That reminds me about a real-life question you could ask your little > daughter: "how many pupils are in each class and in total at school?". > I guess you would send her to extra math courses if she said "Class A > has 20, class B and class C have 25 each, and the school has 0." > This example doesn't claim to be 100% relevant for du, but shows > how "counting" and "summarizing" is burnt into human brains. Personally, I think that du should recount links and command-line arguments everywhere except in the total, as reported by the -c flag. This would add to the information reported by du without violating 1 above. Let's consider an example. I have actually had several people in my office confused over variations of this same problem since du's behavior has changed. If several people have come looking for help, this means that many more are confused and, worse yet, some people/scripts probably haven't even caught the inconsistency. Let's say that I want to answer the following question: What are the sizes of the directories "one" and "two" and "two/three" and all of these directories combined. Perhaps I know that "one" and "two" are often too large and that "three" often causes "two" to grow too large. Below is what my first principals would suggest I do. Interestingly, however, I notice that "two/three" is not reported at all. So my question is not answered. $ du -ksc one two two/three 75096 one 4283824 two 4358920 total Next, I might try reversing the order of arguments to see what happens. Now, I see that all are reported. A hurried user might stop here and go about their day. A sly user will notice, however, that "two/three" appears larger than "two" How is this possible?! $ du -ksc one two/three two 75096 one 3184072 two/three 1099752 two 4358920 total So, I might wander down the hall and visit with a friend. He suggests that I use the --count-links flag to allow recounting (even though there are not multiple links in this scenario). Now, everything is reported and the numbers on each line of output match, but what happened to my total? This can't be right, it's larger than my entire disk quota! $ du -ksc --count-links one two two/three 75096 one 4283824 two 3184072 two/three 7542992 total Turns out that --count-links sums all the output, even those that are recounted, yielding an incorrect total. Finally, I break down and use three commands get the answer I was looking for. Not pretty. $ du -ks one two; du -ks two/three; du -ksc one two | tail -1 75096 one 4283824 two 3184072 two/three 4358920 total Is it just me or does anyone else think this is convoluted?
