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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | STANDARDS | SEE ALSO | AUTHOR | COLOPHON |
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ACL_SET_FILE(3) Library Functions Manual ACL_SET_FILE(3)
acl_set_file, acl_set_file_at — set an ACL by filename
Linux Access Control Lists library (libacl, -lacl).
<sys/types.h> <sys/acl.h> int acl_set_file(const char *path_p,
acl_type_t type, acl_t acl) int acl_set_file_at(int dirfd,
const char *path_p, int at_flags, acl_type_t type, acl_t acl)
The acl_set_file() function associates an access ACL with a file
or directory, or associates a default ACL 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_set_file() operates on
the file or directory the link refers to.
The effective user ID of the process must match the owner of the
file or directory or the process must have the CAP_FOWNER
capability for the request to succeed.
The value of the argument type is used to indicate whether the
access ACL or the default ACL associated with path_p is being set.
If the type parameter is ACL_TYPE_ACCESS, the access ACL of path_p
shall be set. If the type parameter is ACL_TYPE_DEFAULT, the
default ACL of path_p shall be set. If the argument type specifies
a type of ACL that cannot be associated with path_p, then the
function fails.
The acl parameter must reference a valid ACL according to the
rules described on the acl_valid(3) manual page if the type
parameter is ACL_TYPE_ACCESS, and must either reference a valid
ACL or an ACL with zero ACL entries if the type parameter is
ACL_TYPE_DEFAULT. If the acl parameter references an empty ACL,
then the acl_set_file() function removes any default ACL
associated with the directory referred to by the path_p parameter.
acl_set_file_at()
The acl_set_file_at() function operates in exactly the same way as
acl_set_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_set_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_set_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_set_file_at() is similar to that of acl_set_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.
The acl_set_file() and acl_set_file_at() functions return the
value 0 if successful; otherwise the value -1 is returned and the
global variable errno is set to indicate the error.
If any of the following conditions occur, the acl_set_file() and
acl_set_file_at() functions return -1 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 acl does not point to a valid ACL.
The ACL has more entries than the file referred
to by path_p can obtain.
The type parameter is not ACL_TYPE_ACCESS or
ACL_TYPE_DEFAULT.
The type parameter is ACL_TYPE_DEFAULT, but the
file referred to by path_p is not a directory.
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.
[ENOSPC] The directory or file system that would contain
the new ACL cannot be extended or the file
system is out of file allocation resources.
[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 identified by path_p cannot be
associated with the ACL because the file system
on which the file is located does not support
this.
[EPERM] The process does not have appropriate privilege
to perform the operation to set the ACL.
[EROFS] This function requires modification of a file
system which is currently read-only.
IEEE Std 1003.1e draft 17 (“POSIX.1e”, abandoned)
The behavior of acl_set_file() when the acl parameter refers to an
empty ACL and the type parameter is ACL_TYPE_DEFAULT is an
extension in the Linux implementation, in order that all values
returned by acl_get_file() can be passed to acl_set_file(). The
POSIX.1e function for removing a default ACL is
acl_delete_def_file().
Function acl_get_file_at() is a Linux specific extension.
acl_delete_def_file(3), acl_get_file(3), acl_set_fd(3),
acl_valid(3), acl(5)
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>.
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_SET_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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