The acl() and facl() functions get or set the ACL of a file whose name is given by pathp or referenced by the open file descriptor fildes. The nentries argument specifies how many ACL entries fit into buffer aclbufp. The acl() function is used to manipulate ACL on file system objects.

The following values for cmd are supported:

SETACL

nentries ACL entries, specified in buffer aclbufp, are stored in the file's ACL. All directories in the path name must be searchable.

GETACL

Buffer aclbufp is filled with the file's ACL entries. Read access to the file is not required, but all directories in the path name must be searchable.

GETACLCNT

The number of entries in the file's ACL is returned. Read access to the file is not required, but all directories in the path name must be searchable.

Upon successful completion, acl() and facl() return 0 if cmd is SETACL. If cmd is GETACL or GETACLCNT, the number of ACL entries is returned. Otherwise, -1 is returned and errno is set to indicate the error.

The acl() function will fail if:

EACCESS

The caller does not have access to a component of the pathname.

EFAULT

The pathp or aclbufp argument points to an illegal address.

EINVAL

The cmd argument is not GETACL, SETACL, or GETACLCNT; the cmd argument is SETACL and nentries is less than 3; or the cmd argument is SETACL and the ACL specified in aclbufp is not valid.

EIO

A disk I/O error has occurred while storing or retrieving the ACL.

ENOENT

A component of the path does not exist.

ENOSPC

The cmd argument is GETACL and nentries is less than the number of entries in the file's ACL, or the cmd argument is SETACL and there is insufficient space in the file system to store the ACL.

ENOTDIR

A component of the path specified by pathp is not a directory, or the cmd argument is SETACL and an attempt is made to set a default ACL on a file type other than a directory.

ENOSYS

The cmd argument is SETACL and the file specified by pathp resides on a file system that does not support ACLs, or the acl() function is not supported by this implementation.

EPERM

The effective user ID does not match the owner of the file and the process does not have appropriate privilege.

EROFS

The cmd argument is SETACL and the file specified by pathp resides on a file system that is mounted read-only.

See attributes(5) for descriptions of the following attributes:

getfacl(1), setfacl(1), aclcheck(3SEC), aclsort(3SEC)