ACL_GET_FILE(3)

NAME
acl_get_file, acl_get_file_at - get an ACL by filename

LIBRARY
Linux Access Control Lists library (libacl, -lacl).

SYNOPSIS
#include <sys/types.h>
#include <sys/acl.h>
acl_t
acl_get_file(const char *path_p, acl_type_t type);
acl_t
acl_get_file_at(int dirfd, const char *path_p, int at_flags, acl_type_t type);

DESCRIPTION
The acl_get_file() function retrieves the access ACL associated with a file or directory, or the default ACL associated with a directory. The pathname for the file or directory is given in the argument path_p. If path_p is a symbolic link, acl_get_file() returns information about the file or directory the link refers to.

The ACL is placed into working storage and acl_get_file() returns a pointer to that storage.

In order to read an ACL from an object, a process must have read access to the object's attributes.

The value of the argument type is used to indicate whether the access ACL or the default ACL associated with path_p is returned. If type is ACL_TYPE_ACCESS, the access ACL of path_p is returned. If type is ACL_TYPE_DEFAULT, the default ACL of path_p is returned. If type is ACL_TYPE_DEFAULT and no default ACL is associated with the directory path_p, then an ACL containing zero ACL entries is returned. If type specifies a type of ACL that cannot be associated with path_p, then the function fails.

This function may cause memory to be allocated. The caller should free any releasable memory, when the new ACL is no longer required, by calling acl_free(3) with the (void*)acl_t returned by acl_get_file() as an argument.

  acl_get_file_at
The acl_get_file_at() function operates in exactly the same way as acl_get_file(), except for the differences described here.

If the pathname given in path_p is relative, then it is interpreted relative to the directory referred to by the file descriptor dirfd (rather than relative to the current working directory of the calling process, as is done by acl_get_file()).

If path_p is relative and dirfd is the special value AT_FDCWD, then path_p is interpreted relative to the current working directory of the calling process (like acl_get_file()).

If path_p is absolute, then dirfd is ignored.

The at_flags argument can either be 0, or include one or more of the following flags ORed:

AT_EMPTY_PATH
    If path_p is an empty string, operate on the file referred to by dirfd (which may have been obtained using the open(2) O_PATH flag). In this case, dirfd can refer to any type of file, not just a directory, and the behavior of acl_get_file_at() is similar to that of acl_get_fd().

AT_SYMLINK_NOFOLLOW
    If path_p refers to a symbolic link, do not dereference it: instead, fail the operation and set the global variable errno to ENOTSUP. This indicates that the symbolic link cannot have ACLs.

RETURN VALUE
On success, the acl_get_file() and acl_get_file_at() functions return a pointer to the working storage. On error, a value of (acl_t)NULL is returned, and errno is set appropriately.

ERRORS
If any of the following conditions occur, the acl_get_file() and acl_get_file_at() functions return a value of (acl_t)NULL and set errno to the corresponding value:

[EACCES]
    Search permission is denied for a component of the path prefix or the object exists and the process does not have appropriate access rights.

    Argument type specifies a type of ACL that cannot be associated with path_p.

[EBADF]
    The argument path_p is relative but the argument dirfd is neither AT_FDCWD nor a valid file descriptor.

[EINVAL]
    The argument type is not ACL_TYPE_ACCESS or ACL_TYPE_DEFAULT.

    An invalid flag was specified in the at_flags argument.

[ENAMETOOLONG]
    The length of the argument path_p is too long.

[ENOENT]
    The named object does not exist or the argument path_p points to an empty string.

[ENOMEM]
    The ACL working storage requires more memory than is allowed by the hardware or system-imposed memory management constraints.

[ENOTDIR]
    A component of the path prefix is not a directory.

    The argument path_p is relative and the argument dirfd is a file descriptor referring to a file other than a directory.

[ENOTSUP]
    The argument at_flags includes the flag AT_SYMLINK_NOFOLLOW and path_p is a symbolic link.

    The file system on which the file identified by path_p is located does not support ACLs, or ACLs are disabled.

STANDARDS
IEEE Std 1003.1e draft 17 (“POSIX.1e”, abandoned)

Function acl_get_file_at() is a Linux specific extension.

SEE ALSO
acl_free(3), acl_get_entry(3), acl_get_fd(3), acl_set_file(3), acl(5)

AUTHOR
Derived from the FreeBSD manual pages written by Robert N M Watson <rwatson@FreeBSD.org>, and adapted for Linux by Andreas Gruenbacher <andreas.gruenbacher@gmail.com>.