NAME¶

std::filesystem::perms - std::filesystem::perms

Synopsis¶

Defined in header <filesystem>
enum class perms; (since C++17)

This type represents file access permissions.

perms satisfies the requirements of BitmaskType (which means the bitwise operators
operator&, operator|, operator^, operator~, operator&=, operator|=, and operator^=
are defined for this type). none represents the empty bitmask; every other
enumerator represents a distinct bitmask element.

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

Member constants¶

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
File owner has read, write, and
execute/search permissions
owner_all 0700 S_IRWXU
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
The file's user group has read,
write, and execute/search permissions
group_all 070 S_IRWXG
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
Other users have read, write, and
execute/search permissions
others_all 07 S_IRWXO
Equivalent to others_read |
others_write | others_exec
All users have read, write, and
execute/search permissions
all 0777
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
Implementation-defined meaning, but
POSIX XSI specifies that when set on
sticky_bit 01000 S_ISVTX a directory, only file owners may
delete files even if the directory is
writeable to others (used with /tmp)
All valid permission bits.
mask 07777
Equivalent to all | set_uid | set_gid
| sticky_bit

Additionally, the following constants of this type are defined, which do not
represent permissions:

Member constant Value (hex) Meaning
unknown 0xFFFF Unknown permissions (e.g. when filesystem::file_status
is created without permissions)

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 <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");
}

Possible output:¶

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

See also¶

status determines file attributes
symlink_status determines file attributes, checking the symlink target
(C++17) (function)
(C++17)
permissions modifies file access permissions
(C++17) (function)