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std::experi...permissions(3)   C++ Standard Libary  std::experi...permissions(3)

NAME
     std::experimental::filesystem::permissions   -  std::experimental::filesys-
     tem::permissions

Synopsis
	Defined in header <experimental/filesystem>
	void	permissions(	const	  path&     p,	   perms     prms     );
     (filesystem TS)
	void permissions( const path& p, perms prms, error_code& ec );

	Changes  access  permissions  of  the file to which p resolves, as if by
     POSIX fchmodat.
	Symlinks are followed if prms::resolve_symlinks is set.

	The effects depend on prms as follows:

	  * If neither perms::add_perms nor  perms::remove_perms  is  set,  file
     permissions are
	    set  to  exactly prms & fs::perms::mask (meaning, every valid bit of
     prms is
	    applied).
	  * If perms::add_perms, the file permissions are set to exactly
	    status(p).permissions() | (prms & perms::mask) (meaning,  any  valid
     bit that is
	    set  in  prms, but not in the file's current permissions is added to
     the file's
	    permissions).
	  * If perms::remove_perms is set, the file permissions are set  to  ex-
     actly
	    status(p).permissions()  & ~(prms & perms::mask) (meaning, any valid
     bit that is
	    clear in prms, but set in the file's current permissions is  cleared
     in the
	    file's permissions).
	  *  If both perms::add_perms and perms::remove_perms are set, error oc-
     curs.

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

Parameters
	p    - path to examine
	prms - permissions to set, add, or remove
	ec   - out-parameter for error reporting in the non-throwing overload

Return value
	(none)

Exceptions
	The overload that does not take an error_code& parameter throws filesys-
     tem_error on
	underlying OS API errors, constructed with p as the first  argument  and
     the OS error
	code  as the error code argument. std::bad_alloc may be thrown if memory
     allocation
	fails. The overload taking an error_code& parameter sets it  to  the  OS
     API error code
	if  an	OS  API  call fails, and executes ec.clear() if no errors occur.
     This overload
	has
	noexcept specification:
	noexcept

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
	perms	       identifies file system permissions
		       (enum)
	status	       determines file attributes
	symlink_status determines file attributes, checking the symlink target
		       (function)

Categories:
	  * Noindexed pages
	  * unconditionally noexcept

Hidden categories:
	  * Pages with unreviewed unconditional noexcept template
	  * Pages with unreviewed noexcept template

http://cppreference.com 	   2024.06.10	    std::experi...permissions(3)
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