.\" Access Control Lists manual pages .\" .\" (C) 2002-2026 Andreas Gruenbacher .\" .\" This is free documentation; you can redistribute it and/or .\" modify it under the terms of the GNU General Public License as .\" published by the Free Software Foundation; either version 2 of .\" the License, or (at your option) any later version. .\" .\" The GNU General Public License's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" This manual is distributed in the hope that it will be useful, .\" but WITHOUT ANY WARRANTY; without even the implied warranty of .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the .\" GNU General Public License for more details. .\" .\" You should have received a copy of the GNU General Public .\" License along with this manual. If not, see .\" . .\" .Dd June 5, 2026 .Dt ACL_SET_FILE 3 .Os "Linux ACL" .Sh NAME .Nm acl_set_file , .Nm acl_set_file_at .Nd set an ACL by filename .Sh LIBRARY Linux Access Control Lists library (libacl, \-lacl). .Sh SYNOPSIS .In sys/types.h .In sys/acl.h .Ft int .Fo acl_set_file .Fa "const char *path_p" .Fa "acl_type_t type" .Fa "acl_t acl" .Fc .Ft int .Fo acl_set_file_at .Fa "int dirfd" .Fa "const char *path_p" .Fa "int at_flags" .Fa "acl_type_t type" .Fa "acl_t acl" .Fc .Sh DESCRIPTION The .Fn 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 .Va path_p . If .Va path_p is a symbolic link, .Fn acl_set_file operates on the file or directory the link refers to. .Pp 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. .Pp The value of the argument .Va type is used to indicate whether the access ACL or the default ACL associated with .Va path_p is being set. If the .Va type parameter is .Dv ACL_TYPE_ACCESS , the access ACL of .Va path_p shall be set. If the .Va type parameter is .Dv ACL_TYPE_DEFAULT , the default ACL of .Va path_p shall be set. If the argument .Va type specifies a type of ACL that cannot be associated with .Va path_p , then the function fails. .Pp The .Va acl parameter must reference a valid ACL according to the rules described on the .Xr acl_valid 3 manual page if the .Va type parameter is .Dv ACL_TYPE_ACCESS , and must either reference a valid ACL or an ACL with zero ACL entries if the .Va type parameter is .Dv ACL_TYPE_DEFAULT . If the .Va acl parameter references an empty ACL, then the .Fn acl_set_file function removes any default ACL associated with the directory referred to by the .Va path_p parameter. .Ss Fn acl_set_file_at The .Fn acl_set_file_at function operates in exactly the same way as .Fn acl_set_file , except for the differences described here. .Pp If the pathname given in .Va path_p is relative, then it is interpreted relative to the directory referred to by the file descriptor .Va dirfd (rather than relative to the current working directory of the calling process, as is done by .Fn acl_set_file ) . .Pp If .Va path_p is relative and .Va dirfd is the special value .Dv AT_FDCWD , then .Va path_p is interpreted relative to the current working directory of the calling process (like .Fn acl_set_file ) . .Pp If .Va path_p is absolute, then .Va dirfd is ignored. .Pp The .Va at_flags argument can either be 0, or include one or more of the following flags ORed: .Bl -tag .It Dv AT_EMPTY_PATH If .Va path_p is an empty string, operate on the file referred to by .Va dirfd (which may have been obtained using the .Xr open 2 .Dv O_PATH flag). In this case, .Va dirfd can refer to any type of file, not just a directory, and the behavior of .Fn acl_set_file_at is similar to that of .Fn acl_set_fd . .It Dv AT_SYMLINK_NOFOLLOW If .Va path_p refers to a symbolic link, do not dereference it: instead, fail the operation and set the global variable .Va errno to .Er ENOTSUP . This indicates that the symbolic link cannot have ACLs. .El .Sh RETURN VALUE .Rv -std acl_set_file acl_set_file_at .Sh ERRORS If any of the following conditions occur, the .Fn acl_set_file and .Fn acl_set_file_at functions return .Li -1 and set .Va errno to the corresponding value: .Bl -tag -width Er .It Bq Er 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. .Pp Argument .Va type specifies a type of ACL that cannot be associated with .Va path_p . .It Bq Er EBADF The argument .Va path_p is relative but the argument .Va dirfd is neither .Dv AT_FDCWD nor a valid file descriptor. .It Bq Er EINVAL The argument .Va acl does not point to a valid ACL. .Pp The ACL has more entries than the file referred to by .Va path_p can obtain. .Pp The .Va type parameter is not .Dv ACL_TYPE_ACCESS or .Dv ACL_TYPE_DEFAULT . .Pp The .Va type parameter is .Dv ACL_TYPE_DEFAULT , but the file referred to by .Va path_p is not a directory. .Pp An invalid flag was specified in the .Va at_flags argument. .It Bq Er ENAMETOOLONG The length of the argument .Va path_p is too long. .It Bq Er ENOENT The named object does not exist or the argument .Va path_p points to an empty string. .It Bq Er 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. .It Bq Er ENOTDIR A component of the path prefix is not a directory. .Pp The argument .Va path_p is relative and the argument .Va dirfd is a file descriptor referring to a file other than a directory. .It Bq Er ENOTSUP The argument .Va at_flags includes the flag .Dv AT_SYMLINK_NOFOLLOW and .Va path_p is a symbolic link. .Pp The file identified by .Va path_p cannot be associated with the ACL because the file system on which the file is located does not support this. .It Bq Er EPERM The process does not have appropriate privilege to perform the operation to set the ACL. .It Bq Er EROFS This function requires modification of a file system which is currently read-only. .El .Sh STANDARDS IEEE Std 1003.1e draft 17 (\(lqPOSIX.1e\(rq, abandoned) .Pp The behavior of .Fn acl_set_file when the .Va acl parameter refers to an empty ACL and the .Va type parameter is .Dv ACL_TYPE_DEFAULT is an extension in the Linux implementation, in order that all values returned by .Fn acl_get_file can be passed to .Fn acl_set_file . The POSIX.1e function for removing a default ACL is .Fn acl_delete_def_file . .Pp Function .Fn acl_get_file_at is a Linux specific extension. .Sh SEE ALSO .Xr acl_delete_def_file 3 , .Xr acl_get_file 3 , .Xr acl_set_fd 3 , .Xr acl_valid 3 , .Xr acl 5 .Sh AUTHOR Derived from the FreeBSD manual pages written by .An "Robert N M Watson" Aq rwatson@FreeBSD.org , and adapted for Linux by .An "Andreas Gruenbacher" Aq andreas.gruenbacher@gmail.com .