当前位置：网站首页>Day24: file system

The second parameter is a error_code object , By calling error_code Medium message() Method , Whether the output is successfully created . secondly , You cannot create a parent folder and create subfolders in it ( Only single tier directories can be created )

②create_directories(string url) Can create multistage Catalog

notes ： If the path already exists , It will not be cleared .

    filesystem::path url("fileBox");	
	if (!filesystem::exists(url)) 
	{
		cout << " non-existent " << endl;
	}/* Be sure to give priority to detection */
	// Path storage   Do nothing else 
	filesystem::create_directory("fileBox");  // Create a single level directory 
	error_code temp;
	filesystem::create_directory("fileBox/xx",temp);
	cout << temp.message() << endl;
	filesystem::create_directories("a/b/c",temp);  // Create multi-level directory 
	cout << temp.message() << endl;

（2） Delete path

remove_all(string url)

filesystem::remove_all(url);

（3） Get the time when the file was last modified

last_write_time(string url)

Return to one file_time_type type , Need further adjustment time_since_epoch() Method .count() Get the form of timestamp

Last class mainly talked about two ways ： Method of converting timestamp into readable time .
①ctime(&m_tm)
②std::tm* p=localtime(&m_tm);
cout << " Format time ：" << put_time(p, "%F %T") << endl;

notes ： Later, through the following two lines of code to detect the data type ,count() It is not time_t type , So the above two methods are not very effective .

#include<typeinfo>
typeid(m_time).name()

Start with the essence ： The problem is ：(from stack_overflow)

How to convert std::filesystem::file_time_type to time_t?

C++20 Of solution：

const auto fileTime = std::filesystem::last_write_time(filePath);
const auto systemTime = std::chrono::clock_cast<std::chrono::system_clock>(fileTime);
const auto time = std::chrono::system_clock::to_time_t(systemTime);

So the example code is changed to ：

    auto filetime = filesystem::last_write_time("B");
	const auto systemTime = 
        std::chrono::clock_cast<std::chrono::system_clock>(filetime);
	const auto time = std::chrono::system_clock::to_time_t(systemTime);
	std::tm* p = localtime(&time);
	cout << " File change time ：" << put_time(p,"%F %T") << endl;

Two 、 Three categories path class

1. Determine whether this path exists

notes ： It must be filesystem Scope discriminator in bool filesystem::exist(string url)

    #include<iostream>
    #include<filesystem>
	filesystem::path url("file");
	if (!filesystem::exists(url)) 
	{
		cout << " path does not exist " << endl;
	}

2. Get path related properties ：

（i） Get the current path （ii） Get the root directory （iii） Relative paths （iv） Get root name （v） Get the root path

	filesystem::path curURL = filesystem::current_path();
	//C:\Users\team\Desktop\ The first 24 course  C++ file system \filesystem System \path class 
	cout << curURL.string() << endl;    // Double slash becomes single slash 
	cout <<" current path :" << curURL << endl;				// Double slash 
	cout << " root directory :" << curURL.root_directory() << endl;
	cout << " Relative paths :" << curURL.relative_path() << endl;
	cout << " Root name :" << curURL.root_name() << endl;
	cout << " The root path :" << curURL.root_path() << endl;

Output ：
D:\C++\C++ file system \filesystem System \path class
current path :"D:\\C++\\C++ file system \\filesystem System \\path class "
root directory :"\\"
Relative paths :"C++\\C++ file system \\filesystem System \\path class "
Root name :"D:"
The root path :"D:\\"

3、 ... and 、 Three categories file_status class

1. Create file_status object : utilize filesystem::status(string url)

2. Methods in class ：type() Returns one of several enumeration types (filesystem::file_type Medium )

#include <filesystem>
#include <iostream>
#include <string>
#include <fstream>
using namespace std;
void test_file_status(filesystem::file_status x)
{
	switch (x.type()) 
	{
	case filesystem::file_type::regular:
		cout << " Disk files " << endl;
		break;
	case filesystem::file_type::directory:
		cout << " Directory file " << endl;
		break;
	case filesystem::file_type::not_found:
		cout << " directory does not exist " << endl;
		break;
	case filesystem::file_type::unknown:
		cout << " Unrecognized file " << endl;
		break;
	}
}
int main() 
{
	filesystem::create_directory("file");
	filesystem::file_status x = filesystem::status("file");
	test_file_status(x);
	fstream file("file\\test.dat", ios::out | ios::trunc);
	if (!file) 
	{
		cout << " File creation failed !" << endl;
	}
	test_file_status(filesystem::status("file\\test.dat"));
	return 0;
}

Output ：
Directory file
Disk files

Four 、 Three categories file_status class

notes ： If you can't recognize filesystem It must be that the standard is not adjusted c++17 above ！

directory_entry: File entry
dirctory_iterator: Traversal file
recursive_directory_iterator Traverse all ( With recursive traversal of all folders ！！！)

1. Traverse all files in the current directory

// Traverse all files in the current directory ：
void traverseDirectory()
{
	filesystem::path url("D:\\BaiduNetdiskDownload");
	if (!filesystem::exists(url))
	{
		cout << " The current path does not exist " << endl;
		return;
	}
	filesystem::directory_entry input(url);// entrance 
	if (input.status().type() != filesystem::file_type::directory)
	{
		cout << "url Not a directory " << endl;
		return;
	}
	filesystem::directory_iterator dir(url);
	for (auto v : dir)
	{/*path Is a path object */
		cout << v.path().filename() << endl;
	}
}

2. Traverse all files in the current folder ---> Only the current directory

// Traverse all files in the current folder ---> Only the current directory 
void traverseDirectoryAllFile()
{
	filesystem::path url("D:\\BaiduNetdiskDownload");
	if (!filesystem::exists(url))
	{
		cout << " The current path does not exist " << endl;
		return;
	}
	set<string> dirset;
	filesystem::directory_iterator begin(url);
	for (filesystem::directory_iterator end; begin != end; ++begin)
	{
		if (!filesystem::is_directory(begin->path()))
		{
			dirset.insert(begin->path().filename().string());
		}
	}
	for (auto v : dirset)
	{
		cout << v << endl;
	}

}

3. Traverse all folder files under the current folder

recursive_directory_iterator Traverse all ( With recursive traversal of all folders ！！！)

// Traverse all folder files under the current folder 
void traverseAllDirectoryAllFile()
{
	filesystem::path url("D:\\BaiduNetdiskDownload");
	if (!filesystem::exists(url))
	{
		cout << " The current path does not exist " << endl;
		return;
	}
	set<string> dirset;
	//recursive_directory_iterator  Traverse all ( With recursive traversal of all folders ！！！)
	filesystem::recursive_directory_iterator begin(url);
	for (filesystem::recursive_directory_iterator end; begin != end; ++begin)
	{
		if (!filesystem::is_directory(begin->path()))
		{
			dirset.insert(begin->path().filename().string());
		}
	}
	for (auto v : dirset)
	{
		cout << v << endl;
	}

}

4. Delete all files in the current path ( Folder not included ！)

// Delete all files in the current path ( Folder not included ！)
void deleteURLAllFile()
{
	filesystem::path root = filesystem::current_path();
	set<string> dirset;
	for (filesystem::directory_iterator end, begin(root); begin != end; ++begin)
	{
		if (!filesystem::is_directory(begin->path()))/* Exclude folders */
		{
			dirset.insert(begin->path().filename().string());
		}
	}
	for (auto v : dirset)
	{
		if(v!="test.exe")/* The program cannot put itself .exe Delete the file , So we need to rule out */
			filesystem::remove_all(v);	// heavy load /
	}
}

原网站

版权声明
本文为[_ Doris___]所创，转载请带上原文链接，感谢
https://yzsam.com/2022/185/202207042008229370.html