std::filesystem::perm_options

 

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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::file_time_type filesystem::perms filesystem::perm_options filesystem::copy_options filesystem::directory_options
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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::temp_directory_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
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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

 

定义于头文件 <filesystem>
enum class perm_options {     replace = /* unspecified */,     add = /* unspecified */,     remove = /* unspecified */,     nofollow = /* unspecified */ };		(since C++17)

此类型表示可用于控制函数 std::filesystem::permissions() 行为的可用选项。

perm_options 满足 BitmaskType 的要求（这意味着为此类型定义了按位运算符 operator&, operator|, operator^, operator~, operator&=, operator|=, 和 operator^= ）。

成员常量

add、remove、replace 中最多只能存在一个，否则 permissions 函数的行为是未定义的。

成员常量	含义
replace	权限将被 permissions() 的参数完全替换（默认行为）
add	权限将被参数与当前权限的按位 OR 替换
remove	权限将被取反的参数与当前权限的按位 AND 替换
nofollow	权限将在符号链接本身上更改，而不是在其解析到的文件上更改

示例

运行此代码

#include <filesystem>
#include <fstream>
#include <iostream>
 
void demo_perms(std::filesystem::perms p)
{
    using std::filesystem::perms;
    auto show = [=](char op, perms perm)
    {
        std::cout << (perms::none == (perm & p) ? '-' : op);
    };
    show('r', perms::owner_read);
    show('w', perms::owner_write);
    show('x', perms::owner_exec);
    show('r', perms::group_read);
    show('w', perms::group_write);
    show('x', perms::group_exec);
    show('r', perms::others_read);
    show('w', perms::others_write);
    show('x', perms::others_exec);
    std::cout << '\n';
}
 
int main()
{
    std::ofstream("test.txt"); // create file
 
    std::cout << "Created file with permissions: ";
    demo_perms(std::filesystem::status("test.txt").permissions());
 
    std::filesystem::permissions(
        "test.txt",
        std::filesystem::perms::owner_all | std::filesystem::perms::group_all,
        std::filesystem::perm_options::add
    );
 
    std::cout << "After adding u+rwx and g+rwx:  ";
    demo_perms(std::filesystem::status("test.txt").permissions());
 
    std::filesystem::remove("test.txt");
}

可能的输出

Created file with permissions: rw-r--r--
After adding u+rwx and g+wrx:  rwxrwxr--

参见

permissions (C++17)	修改文件访问权限 (函数)
perms (C++17)	标识文件系统权限 (枚举)