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std::experi...stem::perms(3) C++ Standard Libary std::experi...stem::perms(3) NAME std::experimental::filesystem::perms - std::experimental::filesys- tem::perms Synopsis Defined in header <experimental/filesystem> enum class perms; (filesystem TS) 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) 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 Mean- ing 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 exe- cute/search permission File owner has read, write, and execute/search per- missions 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 per- mission The file's user group has read, write, and exe- cute/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 per- missions others_all 07 S_IRWXO Equivalent to oth- ers_read | others_write | oth- ers_exec All users have read, write, and execute/search per- missions 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-de- fined 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 <fstream> #include <bitset> #include <iostream> #include <experimental/filesystem> 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 tar- get (function) permissions modifies file access permissions (function) http://cppreference.com 2022.07.31 std::experi...stem::perms(3)
NAME | Synopsis | Member constants | Notes | Example | Possible output: | See also
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