acl_equiv_mode man page
acl_equiv_mode — check for an equivalent ACL
Linux Access Control Lists library (libacl, -lacl).
acl_equiv_mode(acl_t acl, mode_t *mode_p);
The acl_equiv_mode() function checks if the ACL pointed to by the argument acl contains only the required ACL entries of tag types ACL_USER_OBJ, ACL_GROUP_OBJ, and ACL_OTHER, and contains no permissions other that ACL_READ, ACL_WRITE or ACL_EXECUTE. If the ACL has this form, it can can be fully represented with the traditional file permission bits, and is considered equivalent with the traditional file permission bits.
If acl is an equivalent ACL and the pointer mode_p is not
NULL, the value pointed to by mode_p is set to the value that defines the same owner, group and other permissions as contained in the ACL.
On success, this function returns the value
0 if acl is an equivalent ACL, and the value
1 if acl is not an equivalent ACL. On error, the value
-1 is returned, and errno is set appropriately.
If any of the following conditions occur, the acl_equiv_mode() function returns the value
-1 and sets errno to the corresponding value:
The argument acl is not a valid pointer to an ACL.
This is a non-portable, Linux specific extension to the ACL manipulation functions defined in IEEE Std 1003.1e draft 17 (“POSIX.1e”, abandoned).