std::filesystem::perms
STD：：文件系统：：perms
| Defined in header | | |
|---|---|---|
| enum class perms; | | (since C++17) |
此类型表示文件访问权限。perms满足…的要求BitmaskType%28，这意味着按位运算符operator&，，，operator|，，，operator^，，，operator~，，，operator&=，，，operator|=，和operator^=为此类型%29定义。
访问权限模型POSIX权限位报告的任何单个文件权限%28地位%29是以下几个比特的组合：
成员常数
| Member constant | Value (octal) | POSIX equivalent | Meaning |
|---|---|---|---|
| none | 0 | | no permission bits are set |
| owner_read | 0400 | S_IRUSR | File owner has read permission |
| owner_write | 0200 | S_IWUSR | File owner has write permission |
| owner_exec | 0100 | S_IXUSR | File owner has execute/search permission |
| owner_all | 0700 | S_IRWXU | File owner has read, write, and execute/search permissions Equivalent to owner_read | owner_write | owner_exec. |
| group_read | 040 | S_IRGRP | The file's user group has read permission |
| group_write | 020 | S_IWGRP | The file's user group has write permission |
| group_exec | 010 | S_IXGRP | The file's user group has execute/search permission |
| group_all | 070 | S_IRWXG | The file's user group has read, write, and execute/search permissions Equivalent to group_read | group_write | group_exec. |
| others_read | 04 | S_IROTH | Other users have read permission |
| others_write | 02 | S_IWOTH | Other users have write permission |
| others_exec | 01 | S_IXOTH | Other users have execute/search permission |
| others_all | 07 | S_IRWXO | Other users have read, write, and execute/search permissions Equivalent to others_read | others_write | others_exec. |
| all | 0777 | | All users have read, write, and execute/search permissions Equivalent to owner_all | group_all | others_all. |
| set_uid | 04000 | S_ISUID | Set user ID to file owner user ID on execution |
| set_gid | 02000 | S_ISGID | Set group ID to file's user group ID on execution |
| sticky_bit | 01000 | S_ISVTX | Implementation-defined meaning, but POSIX XSI specifies that when set on a directory, only file owners may delete files even if the directory is writeable to others (used with /tmp) |
| mask | 07777 | | All valid permission bits. Equivalent to all | set_uid | set_gid | sticky_bit. |
此外，定义了以下此类型的常量，这些常量不表示权限：
| Member constant | Value (hex) | Meaning |
|---|---|---|
| unknown | 0xFFFF | Unknown permissions (e.g. when file_status is created without permissions) |
| add_perms | 0x10000 | Control bit that instructs permissions to add, but not clear permission bits. |
| remove_perms | 0x20000 | Control bit that instructs permissions to clear, but not add permission bits |
| resolve_symlinks | 0x40000 | Control bit that instructs permissions to resolve symlinks |
注记
权限可能不一定被实现为位，但它们在概念上被这样对待。
在某些系统上，某些权限位可能被忽略，而更改某些位可能会自动更改其他的%28例如。在没有所有者/组/所有区别的平台上，设置三位写入位中的任意一位设置所有三%29。
例
二次
#include <fstream>
#include <bitset>
#include <iostream>
#include <filesystem>
namespace fs = std::filesystem;
void demo_perms(fs::perms p)
{
std::cout << ((p & fs::perms::owner_read) != fs::perms::none ? "r" : "-")
<< ((p & fs::perms::owner_write) != fs::perms::none ? "w" : "-")
<< ((p & fs::perms::owner_exec) != fs::perms::none ? "x" : "-")
<< ((p & fs::perms::group_read) != fs::perms::none ? "r" : "-")
<< ((p & fs::perms::group_write) != fs::perms::none ? "w" : "-")
<< ((p & fs::perms::group_exec) != fs::perms::none ? "x" : "-")
<< ((p & fs::perms::others_read) != fs::perms::none ? "r" : "-")
<< ((p & fs::perms::others_write) != fs::perms::none ? "w" : "-")
<< ((p & fs::perms::others_exec) != fs::perms::none ? "x" : "-")
<< '\n';
}
int main()
{
std::ofstream("test.txt" // create file
std::cout << "Created file with permissions: ";
demo_perms(fs::status("test.txt").permissions()
fs::permissions("test.txt", fs::perms::add_perms |
fs::perms::owner_all | fs::perms::group_all
std::cout << "After adding o+rwx and g+rwx: ";
demo_perms(fs::status("test.txt").permissions()
fs::remove("test.txt"
}
二次
可能的产出：
二次
Created file with permissions: rw-r--r--
After adding o+rwx and g+wrx: rwxrwxr--
二次
另见
| statussymlink_status (C++17)(C++17) | determines file attributesdetermines file attributes, checking the symlink target (function) |
|---|---|
| permissions (C++17) | modifies file access permissions (function) |
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