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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | STANDARDS | SEE ALSO | AUTHOR | COLOPHON |
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ACL_EXTENDED_FILE(3) Library Functions Manual ACL_EXTENDED_FILE(3)
acl_extended_file, acl_extended_file_at,
acl_extended_file_nofollow — test for information in ACLs by file
name
Linux Access Control Lists library (libacl, -lacl).
<sys/types.h> <acl/libacl.h> int
acl_extended_file(const char *path_p) int
acl_extended_file_at(int dirfd, const char *path_p, int at_flags)
int acl_extended_file_nofollow(const char *path_p)
The acl_extended_file() function returns 1 if the file or
directory whose pathname is given in path_p is associated with an
extended access ACL, or if the directory referred to by path_p is
associated with a default ACL. The function returns 0 if the file
has neither an extended access ACL nor a default ACL. If path_p
is a symbolic link, acl_extended_file() returns information about
the file or directory the link refers to.
An extended ACL is an ACL that contains entries other than the
three required entries of tag types ACL_USER_OBJ, ACL_GROUP_OBJ
and ACL_OTHER. If the result of the acl_extended_file() function
for a file object is 0, then ACLs define no discretionary access
rights other than those already defined by the traditional file
permission bits.
Access to the file object may be further restricted by other
mechanisms, such as Mandatory Access Control schemes. The
access(2) system call can be used to check whether a given type of
access to a file object would be granted.
acl_extended_file_at()
The acl_extended_file_at() function operates in exactly the same
way as acl_extended_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_extended_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_extended_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.
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.
acl_extended_nofollow()
The acl_extended_file_at() function operates in exactly the same
way as acl_extended_file() with a dirfd value of AT_FDCWD and an
at_flags value of AT_SYMLINK_NOFOLLOW.
If successful, these functions return 1 if the file object
referred to by path_p has an extended access ACL or a default ACL,
and 0 if the file object referred to by path_p has neither an
extended access ACL nor a default ACL. Otherwise, the value -1 is
returned and the global variable errno is set to indicate the
error.
If any of the following conditions occur, these functions return
-1 and set errno to the corresponding value:
[EACCES] Search permission is denied for a component of
the path prefix.
[EBADF] The argument path_p is relative but the
argument dirfd is neither AT_FDCWD nor a valid
file descriptor.
[EINVAL] 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.
[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.
This is a non-portable, Linux specific extension to the ACL
manipulation functions defined in IEEE Std 1003.1e draft 17
(“POSIX.1e”, abandoned).
access(2), acl_get_file(3), acl(5)
Written by Andreas Gruenbacher <andreas.gruenbacher@gmail.com>.
This page is part of the acl (manipulating access control lists)
project. Information about the project can be found at
http://savannah.nongnu.org/projects/acl. If you have a bug report
for this manual page, see
⟨http://savannah.nongnu.org/bugs/?group=acl⟩. This page was
obtained from the project's upstream Git repository
⟨git://git.savannah.nongnu.org/acl.git⟩ on 2026-08-03. (At that
time, the date of the most recent commit that was found in the
repository was 2026-06-29.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
Linux ACL June 5, 2026 ACL_EXTENDED_FILE(3)
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HTML rendering created 2026-09-09 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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