home | help 
std::experi...stem::perms(3)   C++ Standard Libary  std::experi...stem::perms(3)

NAME
     std::experimental::filesystem::perms - std::experimental::filesystem::perms

Synopsis
	Defined in header <experimental/filesystem>
	enum class perms;			     (filesystem TS)

	This  type  represents	file access permissions. perms satisfies the re-
     quirements of
	BitmaskType (which means the bitwise operators operator&, operator|, op-
     erator^,
	operator~, operator&=, operator|=, and operator^= are defined  for  this
     type).

	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
	Member constant Value (octal) POSIX equivalent		      Meaning
	none		0			       No  permission  bits  are
     set
	owner_read	 0400	       S_IRUSR		File owner has read per-
     mission
	owner_write	0200	      S_IWUSR	       File owner has write per-
     mission
	owner_exec	 0100		S_IXUSR 	  File	owner  has  exe-
     cute/search
						       permission
						       File   owner   has  read,
     write, and
						       execute/search	 permis-
     sions
	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 exe-
     cute/search
						       permission
						       Other  users  have  read,
     write, and
						       execute/search	 permis-
     sions
	others_all	07	      S_IRWXO
						       Equivalent to others_read
     |
						       others_write    |    oth-
     ers_exec
						       All   users   have  read,
     write, and
						       execute/search	 permis-
     sions
	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  file_status
     is created
				     without permissions)
	add_perms	  0x10000      Control bit that instructs permissions to
     add, but not
				     clear permission bits
	remove_perms	 0x20000     Control bit that instructs  permissions  to
     clear, but
				     not add permission bits
	resolve_symlinks  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

http://cppreference.com 	   2024.06.10	    std::experi...stem::perms(3)
home | help