std::filesystem::exists
Defined in header <filesystem> | | |
|---|---|---|
bool exists( std::filesystem::file_status s ) | (1) | (since C++17) |
bool exists( const std::filesystem::path& p ); bool exists( const std::filesystem::path& p, std::error_code& ec ) | (2) | (since C++17) |
检查给定的文件状态或路径是否与现有文件或目录相对应。
1%29相当于status_known(s) && s.type() != file_type::not_found...
2%29相当于exists(status(p))或exists(status(p, ec))%28符号链接跟随%29。非抛出重载返回。false如果发生错误。
参数
s | - | file status to check |
|---|---|---|
p | - | path to examine |
ec | - | out-parameter for error reporting in the non-throwing overload |
返回值
true如果给定路径或文件状态对应于现有文件或目录，false否则。
例外
1%29
noexcept规格：
noexcept
2%29不占用std::error_code&参数抛文件系统[医]误差关于基础OS API错误，使用p作为第一个参数和操作系统错误代码作为错误代码参数。std::bad_alloc如果内存分配失败，则可能引发。过载std::error_code&参数，如果OSAPI调用失败，则将其设置为OSAPI错误代码，并执行ec.clear()如果没有错误发生。这个过载
noexcept规格：
noexcept
注记
此函数提供的信息通常也是目录迭代的副产品。在目录迭代期间，调用exists(*iterator)比exists(iterator->status())...
例
二次
#include <iostream>
#include <fstream>
#include <cstdint>
#include <filesystem>
namespace fs = std::filesystem;
void demo_exists(const fs::path& p, fs::file_status s = fs::file_status{})
{
std::cout << p;
if(fs::status_known(s) ? fs::exists(s) : fs::exists(p))
std::cout << " exists\n";
else
std::cout << " does not exist\n";
}
int main()
{
fs::create_directory("sandbox");
std::ofstream("sandbox/file"); // create regular file
fs::create_symlink("non-existing", "sandbox/symlink");
demo_exists("sandbox");
for(auto it = fs::directory_iterator("sandbox"); it != fs::directory_iterator(); ++it)
demo_exists(*it, it->status()); // use cached status from directory entry
fs::remove_all("sandbox");
}二次
产出：
二次
"sandbox" exists
"sandbox/file" exists
"sandbox/symlink" does not exist二次
另见
statussymlink_status (C++17)(C++17) | determines file attributesdetermines file attributes, checking the symlink target (function) |
|---|---|
file_status (C++17) | represents file type and permissions (class) |
statussymlink_status | status of the file designated by this directory entrysymlink_status of the file designated by this directory entry (public member function of std::filesystem::directory_entry) |
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