Manipulating the tag type and qualifier in an ACL entry

Updated: May 06, 2022

Each ACL entry must have a tag type, and some also require a qualifier.

Entry type Tag type Qualifier
Owner ACL_USER_OBJ
Named user ACL_USER uid_t
Owning group ACL_GROUP_OBJ
Named group ACL_GROUP gid_t
Mask ACL_MASK
Others ACL_OTHER

The uid_t and gid_t data types are defined in <sys/types.h>.

The ACL entry is an opaque data type, so you need to use these functions to get or set the tag type and the qualifier:

acl_get_qualifier()
Get the qualifier from an ACL entry.
acl_get_tag_type()
Get the type of tag from an ACL entry.
acl_set_qualifier()
Set the qualifier for an ACL entry.
acl_set_tag_type()
Set the tag type of an ACL entry.