Re: a function to get the full path names of a list of files

From:
=?windows-1252?Q?Daniel_Kr=FCgler?= <daniel.kruegler@googlemail.com>
Newsgroups:
comp.lang.c++.moderated
Date:
Thu, 31 Jan 2013 12:40:42 CST
Message-ID:
<kede3q$7ot$1@dont-email.me>
On 2013-01-31 06:35, redstone-cold@163.com wrote:

a function to get the full path names of a list of files
First ,I am not a C++ programmer but a python programmer .I am only a
little familiar with C++ ,so I cannot implement this function myself
,my use of this function is to wrap it into Python to improve my
program??s working efficiency .

I have already know a list of files in a specified directory or its
subdirectories , I need a function to get the full path names of this
list of files ,now I am going to give out the prototype of this
function , I wonder if you can help me to implement this function .

function name : get FullPathNames
parameter : the path to the parent directory that all of that list of
files are contained in, a list of file names the I need to get their
full path names back

return value : a list of full path names


At the current moment, the C++ Standard library does not provide direct
functionality to implement this request, but there exists a proposal to
add a filesystem library to the Library:

http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3505.html

It is based on the existing Boost Filesystem library, see

http://www.boost.org/doc/libs/1_52_0/libs/filesystem/doc/

I have been using boost::filesystem for years and I would recommend to
use it. With a C++11 compiler your function would be written as

#include <algorithm>
#include <iterator>
#include <vector>
#include "boost/filesystem/operations.hpp"

namespace fs = boost::filesystem;

std::vector<fs::path> FullPathNames(const fs::path dir)
{
  std::vector<fs::path> list;
  std::transform(fs::directory_iterator(dir), fs::directory_iterator(),
    std::back_inserter(list), [](const fs::directory_entry& de) { return de.path(); });
  return list;
}

If your compiler does not (yet) lambda expressions, you would rewrite
the code as follows:

#include <algorithm>
#include <iterator>
#include <vector>
#include "boost/filesystem/operations.hpp"

namespace fs = boost::filesystem;

struct PathConverter
{
  fs::path operator()(const fs::directory_entry& de) const { return de.path(); }
};

std::vector<fs::path> FullPathNames(const fs::path dir)
{
  std::vector<fs::path> list;
  std::transform(fs::directory_iterator(dir), fs::directory_iterator(),
    std::back_inserter(list), PathConverter());
  return list;
}

HTH & Greetings from Bremen,

Daniel Kr??gler

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