std::filesystem::directory_entry::exists

 

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技术规范

符号索引

外部库

 

文件系统库

类
filesystem::path filesystem::filesystem_error filesystem::directory_entry filesystem::directory_iterator filesystem::recursive_directory_iterator      filesystem::file_status	filesystem::space_info filesystem::file_type filesystem::perms filesystem::perm_options filesystem::copy_options filesystem::directory_options filesystem::file_time_type
函数
filesystem::absolute filesystem::canonicalfilesystem::weakly_canonical filesystem::relativefilesystem::proximate filesystem::copy filesystem::copy_file filesystem::copy_symlink filesystem::create_directory filesystem::create_directories filesystem::create_hard_link filesystem::create_symlink filesystem::create_directory_symlink filesystem::current_path	filesystem::exists filesystem::equivalent filesystem::file_size filesystem::hard_link_count filesystem::last_write_time filesystem::permissions filesystem::read_symlink filesystem::remove filesystem::remove_all filesystem::rename filesystem::resize_file filesystem::space filesystem::status filesystem::symlink_status filesystem::temp_directory_path
文件类型
filesystem::is_block_file filesystem::is_character_file filesystem::is_directory filesystem::is_empty filesystem::status_known	filesystem::is_fifo filesystem::is_other filesystem::is_regular_file filesystem::is_socket filesystem::is_symlink

 

std::filesystem::directory_entry

成员函数

directory_entry::directory_entry

修改器

directory_entry::operator=

directory_entry::assign

directory_entry::replace_filename

directory_entry::refresh

观察者

directory_entry::pathdirectory_entry::operator const path&

directory_entry::exists

directory_entry::is_block_file

directory_entry::is_character_file

directory_entry::is_directory

directory_entry::is_fifo

directory_entry::is_other

directory_entry::is_regular_file

directory_entry::is_socket

directory_entry::is_symlink

directory_entry::file_size

directory_entry::hard_link_count

directory_entry::last_write_time

directory_entry::statusdirectory_entry::symlink_status

directory_entry::operator==directory_entry::operator!=directory_entry::operator<directory_entry::operator>directory_entry::operator<=directory_entry::operator>=directory_entry::operator<=> (直到 C++20)(直到 C++20)(直到 C++20)(直到 C++20)(直到 C++20)(C++20)

非成员函数

operator<<

 

bool exists() const;	(1)	(自 C++17 起)
bool exists( std::error_code& ec ) const noexcept;	(2)	(自 C++17 起)

检查指向的对象是否存在。实际上返回

1) std::filesystem::exists(status()),

2) std::filesystem::exists(status(ec)).

请注意，status() 会跟踪符号链接到其目标。

参数

ec

-

在非抛出重载中用于错误报告的输出参数

返回值

如果引用的文件系统对象存在，则为 true。

异常

任何未标记为 noexcept 的重载都可能在内存分配失败时抛出 std::bad_alloc。

1) 在底层操作系统 API 错误上抛出 std::filesystem::filesystem_error，使用 p 作为第一个路径参数，并使用操作系统错误代码作为错误代码参数。

2) 如果操作系统 API 调用失败，则将 std::error_code& 参数设置为操作系统 API 错误代码，如果未发生错误，则执行 ec.clear()。

示例

运行此代码

#include <filesystem>
#include <iostream>
 
int main()
{
    for (auto const str:
    {
        "/usr/bin/cat",
        "/usr/bin/mouse",
        "/usr/bin/python",
        "/usr/bin/bison",
        "/usr/bin/yacc",
        "/usr/bin/c++",
    })
    {
        std::filesystem::directory_entry entry{str};
 
        std::cout << "directory entry " << entry
                  << (entry.exists() ? " exists\n" : " does not exist\n");
    }
}

可能的输出

// Output on a POSIX system:
directory entry "/usr/bin/cat" exist
directory entry "/usr/bin/mouse" does not exist
directory entry "/usr/bin/python" exists
directory entry "/usr/bin/bison" exists
directory entry "/usr/bin/yacc" does not exist
directory entry "/usr/bin/c++" exists

另请参见

exists (C++17)

检查路径是否引用现有文件系统对象 (函数)