open() and opendir() functions

Using open() with directories

A new feature on clib4 is the possibility to open() a directory. Of course you can't read() or write() on the directory but you can access the directory using fstat() function for example.

New flags are now supported by open:

O_DIRECTORY

If pathname is not a directory, cause the open to fail.

O_PATH

Obtain a file descriptor that can be used for two purposes:

• to indicate a location in the filesystem tree and to perform operations that act purely at the file descriptor level. The file itself is not opened, and other file operations (e.g., read or write), fail with the error EBADF.

The following operations can be performed on the resulting file descriptor:

• close

• fchdir if the file descriptor refers to a directory

• fstat

• fstatfs

• Duplicating the file descriptor dup, fcntl(F_DUPFD, etc.)

• Getting and setting file descriptor flags fcntl(F_GETFD and F_SETFD)

• Retrieving open file status flags using the fcntl with F_GETFL operation: the returned flags will include the bit O_PATH.

• Passing the file descriptor as the dirfd argument of openat() and the other "at*() system calls.