Search files in directory and subdirectory using boost library c++

Question

I want to create an application that search files in directory and in subdirectory using the boost library for c++ also I don't want to get trouble with UNICODE files like files named arabic . So how can i do that?

UPDATE:

#include <iostream>
#include <boost/filesystem/operations.hpp>
#include <boost/filesystem/fstream.hpp>
#define BOOST_FILESYSTEM_NO_DEPRECATED
using namespace boost::filesystem;
using namespace std;

bool find_file( const path & dir_path,         // in this directory,
                const std::string & file_name, // search for this name,
                path & path_found )            // placing path here if found
{
  if ( !exists( dir_path ) ) return false;
  directory_iterator end_itr; // default construction yields past-the-end
  for ( directory_iterator itr( dir_path );
        itr != end_itr;
        ++itr )
  {
    if ( is_directory(itr->status()) )
    {
      if ( find_file( itr->path(), file_name, path_found ) ) return true;
    }
    else if ( itr->path().filename() == file_name ) // see below
    {
      path_found = itr->path();
      return true;
    }
  }
  return false;
}

int main()
{
    path myPath = "C:";
    string myFile = ".doc";
    path myfound = "c:";

    find_file(myPath, myFile, myfound);
}

I tried also this code but it won't compile it show this error and a lot

undefined reference to `boost::filesystem3::path::filename() const

also:

X:\mingw\boost\boost_1_47_0\boost\system\error_code.hpp|214|undefined reference to `boost::system::generic_category()'|

Answer 1

You have to link against the boost_system and the boost_filesystem libraries. How to do this depends on your compiler/linker combination; for example, on my system I have to add the flags -lboost_system-mt -lboost_filesystem-mt.

Some remarks: On Windows, you usually want wstring (or other "wide character" object) to increase your chance of working with Unicode paths. Second, you can make your code much shorter using find_if and recursive_directory_iterator:

#include <algorithm>
#include <iostream>

#define BOOST_FILESYSTEM_NO_DEPRECATED
#define BOOST_FILESYSTEM_VERSION 3

#include <boost/filesystem.hpp>

using namespace std;
using namespace boost::filesystem;

bool find_file(const path& dir_path, const path& file_name, path& path_found) {
  const recursive_directory_iterator end;
  const auto it = find_if(recursive_directory_iterator(dir_path), end,
                          [&file_name](const directory_entry& e) {
                            return e.path().filename() == file_name;
                          });
  if (it == end) {
    return false;
  } else {
    path_found = it->path();
    return true;
  }
}

int main() {
  const path myPath = L"/usr/local";
  const path myFile = L"filesystem.hpp";
  path myFound;
  find_file(myPath, myFile, myFound);
  wcout << myFound << endl;
}

My example uses the C++11 features auto and lambda, which are present in GCC 4.6. If your compiler lacks these, you can easily replace the lambda by a predicate object and the auto by an explicit type specifier:

#include <functional>

class file_name_equal: public unary_function<path, bool> {
public:
  explicit file_name_equal(const path& fname): file_name(fname) { }

  bool operator()(const directory_entry& entry) const {
    return entry.path().filename() == file_name;
  }

private:
  path file_name;
};

bool find_file_cxx03(const path& dir_path, const path& file_name,
                     path& path_found) {
  const recursive_directory_iterator end;
  const recursive_directory_iterator it =
    find_if(recursive_directory_iterator(dir_path), end,
            file_name_equal(file_name));
  if (it == end) {
    return false;
  } else {
    path_found = it->path();
    return true;
  }
}

Another nice variant gets rid of the return value reference using Boost.Optional:

...
#include <boost/optional.hpp>

using namespace std;
using namespace boost;
using namespace boost::filesystem;

optional<path> find_file(const path& dir_path, const path& file_name) {
  const recursive_directory_iterator end;
  const auto it = find_if(recursive_directory_iterator(dir_path), end,
                          [&file_name](const directory_entry& e) {
                            return e.path().filename() == file_name;
                          });
  return it == end ? optional<path>() : it->path();
}

int main() {
  const path myPath = L"/usr/local";
  const path myFile = L"filesystem.hpp";
  wcout << find_file(myPath, myFile).get_value_or("not found") << endl;
}