std::experi...stem::perms(3)

okay so welcome to the C++ Standard Libary page for std::experimental::filesystem::perms — that's the man page std::experi...stem::perms(3), and we're about to make file permissions make sense, no cap 💖

✨ NAME ✨

std::experimental::filesystem::perms — std::experimental::filesystem::perms (yes bestie, the NAME section said it twice and we're keeping the whole vibe).

🦋 Synopsis 🦋

Defined in header <experimental/filesystem>:

enum class perms;                            (filesystem TS)

So perms is the type that represents file access permissions. It satisfies the requirements of BitmaskType — meaning operator&, operator|, operator^, operator~, operator&=, operator|=, and operator^= are defined for this type. Bitmask icon behavior, periodt ✨

Access permissions model POSIX permission bits, and any individual file permissions (as reported by status) are a combination of some of the following bits:

🎀 Member constants 🎀

The original columns are Member constant, Value (octal), POSIX equivalent, and Meaning — here they are as bullet points so nobody's eyes glaze over 💅

• none — value (octal): 0; POSIX equivalent: none listed. No permission bits are set.
• owner_read — value (octal): 0400; POSIX equivalent: S_IRUSR. File owner has read permission.
• owner_write — value (octal): 0200; POSIX equivalent: S_IWUSR. File owner has write permission.
• owner_exec — value (octal): 0100; POSIX equivalent: S_IXUSR. File owner has execute/search permission.
• owner_all — value (octal): 0700; POSIX equivalent: S_IRWXU. File owner has read, write, and execute/search permissions; equivalent to owner_read | owner_write | owner_exec.
• group_read — value (octal): 040; POSIX equivalent: S_IRGRP. The file's user group has read permission.
• group_write — value (octal): 020; POSIX equivalent: S_IWGRP. The file's user group has write permission.
• group_exec — value (octal): 010; POSIX equivalent: S_IXGRP. The file's user group has execute/search permission.
• group_all — value (octal): 070; POSIX equivalent: S_IRWXG. The file's user group has read, write, and execute/search permissions; equivalent to group_read | group_write | group_exec.
• others_read — value (octal): 04; POSIX equivalent: S_IROTH. Other users have read permission.
• others_write — value (octal): 02; POSIX equivalent: S_IWOTH. Other users have write permission.
• others_exec — value (octal): 01; POSIX equivalent: S_IXOTH. Other users have execute/search permission.
• others_all — value (octal): 07; POSIX equivalent: S_IRWXO. Other users have read, write, and execute/search permissions; equivalent to others_read | others_write | others_exec.
• all — value (octal): 0777; POSIX equivalent: none listed. All users have read, write, and execute/search permissions; equivalent to owner_all | group_all | others_all.
• set_uid — value (octal): 04000; POSIX equivalent: S_ISUID. Set user ID to file owner user ID on execution.
• set_gid — value (octal): 02000; POSIX equivalent: S_ISGID. Set group ID to file's user group ID on execution.
• sticky_bit — value (octal): 01000; POSIX equivalent: 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 — value (octal): 07777; POSIX equivalent: none listed. All valid permission bits; equivalent to all | set_uid | set_gid | sticky_bit.

Additionally, the following constants of this type are defined, which do not represent permissions. The columns are Member constant, Value (hex), and Meaning:

• unknown — value (hex): 0xFFFF. Unknown permissions (e.g. when file_status is created without permissions).
• add_perms — value (hex): 0x10000. Control bit that instructs permissions to add, but not clear permission bits.
• remove_perms — value (hex): 0x20000. Control bit that instructs permissions to clear, but not add permission bits.
• resolve_symlinks — value (hex): 0x40000. Control bit that instructs permissions to resolve symlinks.

💀 Notes 💀

Permissions may not necessarily be implemented as bits, but they are treated that way conceptually.

Some permission bits may be ignored on some systems, and changing some bits may automatically change others (e.g. on platforms without owner/group/all distinction, setting any of the three write bits set all three).

🔥 Example 🔥

       // Run this code

        #include <bitset>
        #include <experimental/filesystem>
        #include <fstream>
        #include <iostream>
        namespace fs = std::experimental::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");
        }

Possible output:

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

🔍 See also 🔍

• status — determines file attributes.
• symlink_status — determines file attributes, checking the symlink target (function).
• permissions — modifies file access permissions (function).

🌈 Category 🌈

• Noindexed pages

okay that's the whole page, bestie 🫶 — source/version: http://cppreference.com; date: 2024.06.10; page: std::experi...stem::perms(3). bye and slay 💅