Quoting Vincent Lefevre (vinc...@vinc17.net): > On 2015-04-24 19:41:03 -0500, David Wright wrote: > > Well, that's what I thought, because of the cacheing. But Nicolas > > asked me to try using thousands of files, and so here we are, > > ie, your "new test": > > > > ~ $ for j in `seq 10000` ; do mkdir /tmp/testdir/file$j ; done > > ~ $ ./a.out /tmp/testdir/ > lsout1 > > ~ $ ./a.out /tmp/testdir/ > lsout2 ← here I renamed file2621 > > ~ $ ./a.out /tmp/testdir/ > lsout3 > > ~ $ wc lsout* > > 10003 40009 237834 lsout1 > > 10002 40005 237809 lsout2 ← missing entry > > 10003 40009 237890 lsout3 > > 30008 120023 713533 total > > ~ $ > [...] > > So we have a file gone AWOL because it was renamed during this > > program's execution. (The I numbers here come from dirent; > > there's no call of stat.) > > So, I would say that this is a bug. POSIX says in > http://pubs.opengroup.org/onlinepubs/9699919799/functions/readdir.html
It may well be. But I'm just presenting facts about the filesystems that I assumed you were using when you posted https://lists.debian.org/debian-user/2015/04/msg00651.html , not the theory of a POSIX-compliant system. > If a file is removed from or added to the directory after the most > recent call to opendir() or rewinddir(), whether a subsequent call > to readdir() returns an entry for that file is unspecified. > > But when a file is renamed, it is nowhere said that the file is > removed from and/or added to the directory. The POSIX spec just > says that the file is "renamed". > > [...] > > You said that without "Bob's move", you couldn't miss an entry that > > hasn't been removed. > > > > I've demonstrated that you can. > > Because of a *bug*. With a conforming implementation, you can't. > > (And if a renamed file were regarded as an entry that was removed, > then this would mean that your example would not be correct, because > this would not be "an entry that hasn't been removed".) It may be a bug. It may be a misfeature in the interests of performance. I don't know. When writing big programs, decisions have to be taken. But my demonstration stands. If you want to reject my observations by bringing in POSIX-compliance as a precondition for my tests, that would be both inconsiderate (ie you'd be telling me I've wasted my time doing all the tests that you encouraged me to perform), and a post disputation argument. This thread would have taken a different course if you'd posted "But with a POSIX-compliant filesystem, as ext3/4 is supposed to be, you can't miss an entry that hasn't been removed." Then I could have looked at the docs and skipped all the tests. Cheers, David. -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: https://lists.debian.org/20150425030137.GD13410@alum
