std::filesystem::permissions

Since C++17

Header: <filesystem>

Changes access permissions of the file to which p resolves, as if by POSIX fchmodat. Symlinks are followed unless perm_options::nofollow is set in opts.

# Declarations

void permissions( const std::filesystem::path& p,
std::filesystem::perms prms,
std::filesystem::perm_options opts = perm_options::replace );

(since C++17)

void permissions( const std::filesystem::path& p,
std::filesystem::perms prms,
std::error_code& ec ) noexcept;

(since C++17)

void permissions( const std::filesystem::path& p,
std::filesystem::perms prms,
std::filesystem::perm_options opts,
std::error_code& ec );

(since C++17)

# Parameters

# Return value

(none)

# 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

#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");
}

# See also