Re: [boost] [filesystem] How to remove specific files from a directory?

7 Sep 2016


      On 7 September 2016 at 16:45, Andrey Semashev  wrote:
...
On 09/07/16 17:07, Mateusz Loskot wrote:
...
On 7 September 2016 at 15:46, Andrey Semashev  wrote:
...
On 09/07/16 16:06, Andrzej Krzemienski wrote:
...
Hi,
I wonder what is boost::filesystem recommendation for solving the
following
problem.
I want to remove all files from a given directory that satisfy a certain
predicate, e.g., only these whose names start with letter "s".
It is my understanding that the calling filesystem::remove may
invalidate
the iterator, and therefore the following solution is incorrect:
fsys::directory_iterator it{path}, itEnd{};
for ( ; it != itEnd ; ++it )
{
  if (predicate(*it))
    fsys::remove(it->path());
}
But, is the following guaranteed to work?:
fsys::directory_iterator it{path}, itEnd{};
for ( ; it != itEnd ; )
{
  if (predicate(*it))
    fsys::remove((it++)->path());
  else
    ++it;
}
From the documentation, it seems the behavior should be similar to
readdir,
in which case it would seem that both pieces of code above are valid.
Indeed, boost::filesystem and std::filesystem (ISO/IEC TS 18822:2015) as
well
as POSIX readdir behave in the same way.
But, for all of them, behaviour is unspecified in case content of
directory that is
being traversed changes.
It is unspecified whether the removed/added files will be discovered as part
of the traversal. Other than that the behavior is defined. For instance, the
implementation should not crash and the iterator should still reach the end
at some point.
Right, the iteration following any changes in the filesystem content
remains valid.
Thanks for the correction.


Best regards,
-- 
Mateusz Loskot, http://mateusz.loskot.net