Changes access permissions of the file to whichp resolves, as if by POSIXfchmodat. Symlinks are followed ifprms::resolve_symlinks is set.

The effects depend onprms as follows:

• If neitherperms::add_perms norperms::remove_perms is set, file permissions are set to exactlyprms& fs::perms::mask (meaning, every valid bit ofprms is applied).
• Ifperms::add_perms, the file permissions are set to exactlystatus(p).permissions()|(prms& perms::mask) (meaning, any valid bit that is set inprms, but not in the file's current permissions is added to the file's permissions).
• Ifperms::remove_perms is set, the file permissions are set to exactlystatus(p).permissions()& ~(prms& perms::mask) (meaning, any valid bit that is clear inprms, but set in the file's current permissions is cleared in the file's permissions).
• If bothperms::add_perms andperms::remove_perms are set, error occurs.

The non-throwing overload has no special action on error.

[edit]Parameters

[edit]Return value

(none)

[edit]Exceptions

[edit]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).

[edit]Example

#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");}

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

[edit]See also