---
name: "acl_valid"
section: "3"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["linux", "freebsd", "macos"]
url: "https://new.carta.tech/acl_valid"
---

# acl\_valid(3)

validate an ACL

## NAME

**acl\_valid**, **acl\_valid\_fd\_np**, **acl\_valid\_file\_np**, **acl\_valid\_link\_np** – validate an ACL

## LIBRARY

Standard C Library (libc, -lc)

## SYNOPSIS

**#include \<sys/types.h\>**

**#include \<sys/acl.h\>**

*int*\

**acl\_valid**(*acl\_t acl*);

*int*\

**acl\_valid\_fd\_np**(*int fd*, *acl\_type\_t type*, *acl\_t acl*);

*int*\

**acl\_valid\_file\_np**(*const char \*path\_p*, *acl\_type\_t type*, *acl\_t acl*);

*int*\

**acl\_valid\_link\_np**(*const char \*path\_p*, *acl\_type\_t type*, *acl\_t acl*);

## DESCRIPTION

These functions check that the ACL referred to by the argument *acl* is valid. The POSIX.1e routine, **acl\_valid**(), checks this validity only with POSIX.1e ACL semantics, and irrespective of the context in which the ACL is to be used. The non-portable forms, **acl\_valid\_fd\_np**(), **acl\_valid\_file\_np**(), and **acl\_valid\_link\_np**() allow an ACL to be checked in the context of a specific acl type, *type*, and file system object. In environments where additional ACL types are supported than just POSIX.1e, this makes more sense. Whereas **acl\_valid\_file\_np**() will follow the symlink if the specified path is to a symlink, **acl\_valid\_link\_np**() will not.

For POSIX.1e semantics, the checks include:

- The three required entries (ACL\_USER\_OBJ, ACL\_GROUP\_OBJ, and ACL\_OTHER) shall exist exactly once in the ACL. If the ACL contains any ACL\_USER, ACL\_GROUP, or any other implementation-defined entries in the file group class then one ACL\_MASK entry shall also be required. The ACL shall contain at most one ACL\_MASK entry.

- The qualifier field shall be unique among all entries of the same POSIX.1e ACL facility defined tag type. The tag type field shall contain valid values including any implementation-defined values. Validation of the values of the qualifier field is implementation-defined.

The POSIX.1e **acl\_valid**() function may reorder the ACL for the purposes of verification; the non-portable validation functions will not.

## IMPLEMENTATION NOTES

FreeBSD's support for POSIX.1e interfaces and features is still under development at this time.

## RETURN VALUES

The **acl\_valid()** function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

## ERRORS

If any of the following conditions occur, these functions shall 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.

- \[EBADF\]

  The *fd* argument is not a valid file descriptor.

- \[EINVAL\]

  Argument *acl* does not point to a valid ACL.

  One or more of the required ACL entries is not present in *acl*.

  The ACL contains entries that are not unique.

  The file system rejects the ACL based on fs-specific semantics issues.

- \[ENAMETOOLONG\]

  A component of a pathname exceeded 255 characters, or an entire path name exceeded 1023 characters.

- \[ENOENT\]

  The named object does not exist, or the *path\_p* argument points to an empty string.

- \[ENOMEM\]

  Insufficient memory available to fulfill request.

- \[EOPNOTSUPP\]

  The file system does not support ACL retrieval.

## SEE ALSO

[acl(3)](/acl/3.md), [acl\_get(3)](/acl_get/3.md), [acl\_init(3)](/acl_init/3.md), [acl\_set(3)](/acl_set/3.md), [posix1e(3)](/posix1e/3.md)

## STANDARDS

POSIX.1e is described in IEEE POSIX.1e draft 17. Discussion of the draft continues on the cross-platform POSIX.1e implementation mailing list. To join this list, see the FreeBSD POSIX.1e implementation page for more information.

## HISTORY

POSIX.1e support was introduced in FreeBSD 4.0, and development continues.

## AUTHORS

Robert N M Watson