C++17 std::filesystem 用法指北

写在最前：std::filesystem 需要C++17或以上的支持，如果你也是使用visual studio开发，那么可以通过 项目属性 > 配置属性 > C/C++ > 语言 > C++语言标准 进行设置。

本文将针对常用的场景，对std::filesystem的使用逐一进行验证：

• <1> 判断文件夹是否存在
• <2> 创建单层目录
• <3> 逐级创建多层目录
• <4> 创建多级目录
• <5> 当前文件路径
• <6> 创建文件"from.dat"
• <7> 获取相对于base的绝对路径
• <8> 文件拷贝
• <9> 移动文件或重命名
• <10> 创建文件 “example.dat”
• <11> 获取文件大小
• <12> 获取文件最后修改时间
• <13> 删除文件
• <14> 递归删除目录下所有文件
• <15> 在临时文件夹下创建文件夹并删除

示例代码

#include 
#include 
#include 
#include 
#include 
#include 
using namespace std;
namespace fs = std::filesystem;

int main() 
{
	cout << "fs demo:\n" << std::boolalpha;

	//<1> 判断文件夹是否存在
	string dirName("log");
	fs::path url(dirName);
	if (!fs::exists(url)) {
		cout << std::quoted(dirName) << " not exist" << "\n";
	}
	else {
		cout << std::quoted(dirName) << " not exist" << "\n";
	}

	//<2> 创建单层目录
	bool okey = fs::create_directory(dirName);
	cout << "create_directory(" << std::quoted(dirName) << "), result=" << okey << "\n";

	//<3> 逐级创建多层目录
	error_code err;
	string subDir = dirName + "/subdir";
	okey = fs::create_directory(subDir, err);
	cout << "create_directory(" << std::quoted(subDir) << "), result=" << okey << "\n";
	cout << "err.value()=" << err.value() << " err.message()=" << err.message() << "\n";

	//<4> 创建多级目录
	dirName = "a/b//c/d/";
	okey = fs::create_directories(dirName, err);
	cout << "create_directories(" << std::quoted(dirName) << "), result=" << okey << "\n";
	cout << "create_directories, err.value()=" << err.value() << " err.message()=" << err.message() << "\n";

	//<5> 当前文件路径
	fs::path currentPath = fs::current_path();//C:\Users\Kandy\Desktop\fs\fs
	cout << "currentPath:\t" << currentPath << "\n";//当前路径
	cout << "root_directory:\t" << currentPath.root_directory() << "\n";//根目录
	cout << "relative_path:\t" << currentPath.relative_path() << "\n";//相对路径
	cout << "root_name:\t" << currentPath.root_name() << "\n";//根名
	cout << "root_path:\t" << currentPath.root_path() << "\n";//根路径

	//<6> 创建文件"from.dat"
	fs::path oldPath(fs::current_path() / "from.dat");
	fstream file(oldPath, ios::out | ios::trunc);
	if (!file) {
		cout << "create file(" << oldPath.string() << ") failed!" << "\n";
	}
	file.close();

	//<7> 获取相对于base的绝对路径
	fs::path absPath = fs::absolute(oldPath/*, fs::current_path()*/);
	cout << "absPath=" << absPath.string() <<"\n";//"C:\Users\Kandy\Desktop\filesystem\filesystem\from.dat"

	//<8> 文件拷贝
	fs::create_directories(fs::current_path() / "to");
	fs::path toPath(fs::current_path() / "to/from0.dat");
	fs::copy(oldPath, toPath);

	//<9> 移动文件或重命名
	fs::path newPath(fs::current_path() / "to/to.dat");
	fs::rename(oldPath, newPath);

	//<10> 创建文件 "example.dat"
	fs::path _path = fs::current_path() / "example.dat";
	cout << "example.dat path:" << std::quoted(_path.string()) << "\n";
	std::ofstream(_path).put('a'); // create file of size 1
	std::ofstream(_path).close();

	//文件类型判定
	assert(fs::file_type::regular == fs::status(_path).type());

	//<11> 获取文件大小
	auto size = fs::file_size(_path);
	cout << "file_size=" << size << endl;

	//<12> 获取文件最后修改时间
	auto time = fs::last_write_time(_path);
	cout << "last_write_time=" << time.time_since_epoch().count() << endl;

	//<13> 删除文件
	okey = fs::remove(_path);
	cout << "remove(" << std::quoted(_path.string()) << ")" << okey << endl;

	//<14> 递归删除目录下所有文件,返回被成功删除的文件个数
	uintmax_t count = fs::remove_all(dirName);//dirName="a/b//c/d/",会把d目录也删掉
	cout << "remove_all(" << std::quoted(dirName) << ")" << count << endl;

	//<15> 在临时文件夹下创建文件夹并删除
	fs::path tmp = fs::temp_directory_path();//"C:\Users\Kandy\AppData\Local\Temp\"
	cout << "temp_directory_path=" << std::quoted(tmp.string()) << endl;
	fs::create_directories(tmp / "_abcdef/example");
	std::uintmax_t n = fs::remove_all(tmp / "_abcdef");
	std::cout << "Deleted " << n << " files or directories\n";

	return 0;
}
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C++官方文档

链接地址：https://en.cppreference.com/w/cpp/filesystem