如何检查目录中是否有新文件？

Question

给定：

• filesystem::path toDir("./");
• ptime oldTime;
• ptime now(second_clock::local_time());

如何我可以确定哪些文件是在 oldTime 和 now 之间的时间段内创建的吗？

此类“新鲜”文件的名称应流式传输到cout。

更新： 根据给定的答案，我做了一个小程序：

#include <sstream>
#include <stdio.h>
#include <time.h>
#include <boost/filesystem.hpp>
#include <boost/thread.hpp>
#include <boost/timer.hpp>
#include <boost/date_time.hpp>
#include <boost/date_time/posix_time/posix_time.hpp>
#include <boost/date_time/posix_time/posix_time_io.hpp>

using namespace boost::filesystem;
using namespace boost::posix_time;
using namespace boost::local_time;
using namespace boost::gregorian;
using namespace std;

path file_service_default_path;

boost::timer timerFame;
int64_t desiredTimeFame;
int64_t spendedTimeFame;
ptime oldTime;
ptime nowTime;
bool first_time;

string file_service_get_dif_path(path base_path, path new_path)
{
    path sdiffpath;
    path stmppath = new_path;
    while(stmppath != base_path) {
        sdiffpath = path(stmppath.stem().string() + stmppath.extension().string())/ sdiffpath;
        stmppath = stmppath.parent_path();
    }
    string diff_path =sdiffpath.string();// boost::lexical_cast<string>(sdiffpath);
    diff_path = diff_path.substr(0, (diff_path.length()));
    std::replace(diff_path.begin(), diff_path.end(), '\\', '/');
    return diff_path;
}

void is_file(path p)
{
    std::string a =  file_service_get_dif_path(file_service_default_path, p);
    std::cout << "File: " <<  a << std::endl;
}

void is_new_file(path p)
{
    std::time_t t = boost::filesystem::last_write_time( p );
    ptime lastAccessTime = from_time_t( t );
    if ( lastAccessTime >= oldTime && lastAccessTime <= nowTime )
    {
        std::string a =  file_service_get_dif_path(file_service_default_path, p);
        std::cout << "File: " <<  a << " is new to us." << std::endl;
    }   
}

void is_dir(path dir)
{
    boost::filesystem::directory_iterator dirIter( dir ), dirIterEnd;
    while ( dirIter != dirIterEnd )
    {
        if ( boost::filesystem::exists( *dirIter ) && !boost::filesystem::is_directory( *dirIter ) )
        {
            if (first_time)
            {
                is_file((*dirIter));
            }
            else
            {
                is_new_file((*dirIter));
            }
        }
        else
        {
            is_dir((*dirIter));
        }
        ++dirIter;
    }
}

void files_walker()
{
    while(true)
    {
        timerFame.restart();
        oldTime = nowTime;
        nowTime = second_clock::local_time() ;
        file_service_default_path = file_service_default_path;
        is_dir(file_service_default_path);
        first_time = false;
        spendedTimeFame = (int64_t)timerFame.elapsed();
        cout << spendedTimeFame << std::endl;
        if (spendedTimeFame < desiredTimeFame)
            boost::this_thread::sleep(boost::posix_time::milliseconds(desiredTimeFame - spendedTimeFame));
    }
}

int main()
{
    desiredTimeFame = (int64_t)(5000.0f);
    first_time = true;
    file_service_default_path = "./new";
    boost::thread workerThread(files_walker);
    cin.get();
}

但似乎没有显示任何新文件=（如何修复它？

更新2：

用nowTime解决= secondary_clock::universal_time();

更新 3： 固定代码：

#include <sstream>
#include <stdio.h>
#include <time.h>
#include <boost/filesystem.hpp>
#include <boost/thread.hpp>
#include <boost/timer.hpp>
#include <boost/date_time.hpp>
#include <boost/date_time/posix_time/posix_time.hpp>
#include <boost/date_time/posix_time/posix_time_io.hpp>

using namespace boost::filesystem;
using namespace boost::posix_time;
using namespace boost::local_time;
using namespace boost::gregorian;
using namespace std;

path file_service_default_path;

boost::timer timerFame;
int64_t desiredTimeFame;
int64_t spendedTimeFame;
ptime oldTime;
ptime nowTime;
bool first_time;

string file_service_get_dif_path(path base_path, path new_path)
{
    path sdiffpath;
    path stmppath = new_path;
    while(stmppath != base_path) {
        sdiffpath = path(stmppath.stem().string() + stmppath.extension().string())/ sdiffpath;
        stmppath = stmppath.parent_path();
    }
    string diff_path =sdiffpath.string();// boost::lexical_cast<string>(sdiffpath);
    diff_path = diff_path.substr(0, (diff_path.length()));
    std::replace(diff_path.begin(), diff_path.end(), '\\', '/');
    return diff_path;
}

void is_file(path p)
{
    std::string a =  file_service_get_dif_path(file_service_default_path, p);
    std::cout << "File: " <<  a << std::endl;
}

void is_new_file(path p)
{
    std::time_t t = boost::filesystem::last_write_time( p );
    ptime lastAccessTime = from_time_t( t );
    if ( lastAccessTime >= oldTime && lastAccessTime <= nowTime )
    {
        std::string a =  file_service_get_dif_path(file_service_default_path, p);
        std::cout << "File: " <<  a << " is new to us." << std::endl;
    }   
}

void is_dir(path dir)
{
    if(!exists(dir))
    {
        return;
    }
    boost::filesystem::directory_iterator dirIter( dir );
    boost::filesystem::directory_iterator dirIterEnd;
    while ( dirIter != dirIterEnd )
    {
        if ( boost::filesystem::exists( *dirIter ) && !boost::filesystem::is_directory( *dirIter ) )
        {
            if (first_time)
            {
                is_file((*dirIter));
            }
            else
            {
                is_new_file((*dirIter));
            }
        }
        else
        {
            is_dir((*dirIter));
        }
        ++dirIter;
    }
}

void files_walker()
{
    while(true)
    {
        timerFame.restart();
        oldTime = nowTime;
        nowTime = second_clock::universal_time();
        is_dir(file_service_default_path);
        first_time = false;
        spendedTimeFame = (int64_t)timerFame.elapsed();
        cout << spendedTimeFame << std::endl;
        if (spendedTimeFame < desiredTimeFame)
            boost::this_thread::sleep(boost::posix_time::milliseconds(desiredTimeFame - spendedTimeFame));
    }
}

int main()
{
    desiredTimeFame = (int64_t)(5000.0f);
    first_time = true;
    file_service_default_path = "./new";
    boost::thread workerThread(files_walker);
    cin.get();
}

Answer 1

正如 Emile Cormier 所说，您将无法在 Unix 中获取文件创建时间。但是，您仍然可以通过查看上次访问时间来查找“新鲜”文件，具体取决于您对“新鲜”的定义。这是通过如下调用实现的：

boost::filesystem::path p( "somefile" );
std::time_t t = boost::filesystem::last_write_time( p );
boost::ptime lastAccessTime = boost::ptime::from_time_t( t );

因此，如果您随后查看 boost::filesystem::directory_iterator ，您就可以迭代目录，即“./”，如您在问题中所述，并将上例中给出的 lastAccessTime 与您的问题中指定的范围进行比较。

因此，假设先前已经定义了oldTime，我的方法如下：

boost::filesystem::path dir( "./" );
boost::ptime nowTime( boost::second_clock::local_time() );

boost::filesystem::directory_iterator dirIter( dir ), dirIterEnd;
while ( dirIter != dirIterEnd )
{
    if ( boost::filesystem::exists( *dirIter ) && !boost::filesystem::is_directory( *dirIter ) )
    {
        std::time_t t = boost::filesystem::last_write_time( *dirIter );
        boost::ptime lastAccessTime = boost::ptime::from_time_t( t );
        if ( lastAccessTime >= oldTime && lastAccessTime <= nowTime )
        {
            std::cout << "File meets criteria: " << (*dirIter).filename() << std::endl;
        }     
    }
    ++dirIter;
}

希望这会有所帮助！

您可以通过持久存储上次检查目录的时间和/或上次检查时目录中存在的最后一个文件列表来完善这一点，并将其用作比较点。如果没有更多关于您意图的信息，我无法提供进一步的指导。

相关文档：
boost::filesystem 参考, boost::ptime 参考