Re: Boost.Filesystem: Reverse directory iterators?

From:

Alberto Ganesh Barbati <AlbertoBarbati@libero.it>

Newsgroups:

comp.lang.c++.moderated

Date:

Tue, 27 May 2008 16:47:43 CST

Message-ID:

<oL__j.322473$%k.408974@twister2.libero.it>

Rune Allnor ha scritto:

Hi all.

I would like to remove a directory tree using Boost.Filesystem.
This code lists the contents of a directory with root p:

/////////////////////////////////////////////////////////////////////
void searchTree(const boost::filesystem::path p)
{
    boost::filesystem::recursive_directory_iterator end_itr;
    for(boost::filesystem::recursive_directory_iterator i(p);
         i!=end_itr;
         ++i)
    {
       // Prints contents of tree
       std::cout << i->string().c_str() << std::endl;
    }

    return;
}
/////////////////////////////////////////////////////////////////////

Unfortunately, the contents of the directory tree is listed in an
order which prevents me from calling a remove() method to the
listed leafs: The name of the directory is listed before the
contents of the directory. According to the docs one can't use
successfully remove() on a directory if the contents have not
been removed first.

According to Boost docs: "The order of directory entries obtained by
dereferencing successive increments of a basic_directory_iterator is
unspecified." So you should not rely on the fact that the directories
are listed first.

What would be needed is a reverse_recursive_directory_iterator
(in style with the standard STL iterator/reverse_iterators pairs)
but I can't find such a thing mentioned in the Boost.Filesystem
documentation, and the compiler complains loudly when I try to
declare one.

Directory iterators are "input" iterators, therefore they can't be
reversed (only "bidirectonal" iterator can be reversed). Anyway, as I
said before, reversing would not solve your problem.

What is the least cumbersome way to iterate from the last
to the first element? I could, of course, use a dummy iterator
to scan for the last element and then reverse iterate back towards
the beginning, but if there is a more elegant solution available...

Just do the loop twice, in the first loop you can use is_directory() to
skip the directories and remove just the files. Then loop again and
remove the directories.

HTH,

Ganesh

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