---
name: "acl_valid"
section: "3"
platform: "linux"
package: "acl"
version: "2.4.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd", "macos"]
url: "https://new.carta.tech/acl_valid"
---

# acl\_valid(3)

validate an ACL

## NAME

**acl\_valid** – validate an ACL

## LIBRARY

Linux Access Control Lists library (libacl, -lacl).

## SYNOPSIS

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

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

*int*\

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

## DESCRIPTION

The **acl\_valid**() function checks the ACL referred to by the argument *acl* for validity.

The three required entries ACL\_USER\_OBJ, ACL\_GROUP\_OBJ, and ACL\_OTHER must exist exactly once in the ACL. If the ACL contains any ACL\_USER or ACL\_GROUP entries, then an ACL\_MASK entry is also required. The ACL may contain at most one ACL\_MASK entry.

The user identifiers must be unique among all entries of type ACL\_USER. The group identifiers must be unique among all entries of type ACL\_GROUP.

## RETURN VALUE

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, the **acl\_valid**() function returns -1 and sets *errno* to the corresponding value:

- \[EINVAL\]

  The argument *acl* is not a valid pointer to an ACL.

  The 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.

## STANDARDS

IEEE Std 1003.1e draft 17 (“POSIX.1e”, abandoned)

## SEE ALSO

[acl\_check(3)](/acl_check/3.md), [acl\_set\_file(3)](/acl_set_file/3.md), [acl(5)](/acl/5.md)

## AUTHOR

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⟩.